| AUTOR | AFILIACJA | TYTUŁ | ABSTRAKT | SŁOWA KLUCZOWE | ROK | VOL | ISSUE | STRONY | DOI | TYTUŁ CZASOPISMA |
|---|---|---|---|---|---|---|---|---|---|---|
| Regad Abdelmalek 1 Kacimi Noureddine 1 Mebarki Hichem 1 Mohamed Ikhlef Chaouch 1 Djedai Hayette 1 Nehila Abdelhak 2 Damba Nadhir 3 Oudrane Abdellatif 3 | 1)Center of Research in Mechanics (CRM), BP N73B, Freres Ferrad, Ain El Bey, Constantine, 25021-Algeria 2) Department of Research in Space Mechanics, Satellite Development Center, Algerian Space Agency, Oran, Algeria 3) Mechanical Department, University of Ahmed Draïa, Adrar, Algeria | J-INTEGRAL ANALYSIS OF CRACK BEHAVIOR IN COMPOSITE MATERIAL GEOMETRIES | This study investigates the influence of geometric discontinuities specifically, circular holes – on the fracture behavior of fiber-reinforced polymer composite plates containing edge cracks. Using the Finite Element Method (FEM) as a non-destructive numerical tool, we analyze how variations in hole size and positioning affect the stress distribution σyy and the J-integral near the crack tip. The J-integral, used both as a fracture toughness parameter and a crack detection indicator, effectively captures the energy release rate and the severity of crack-tip conditions in anisotropic composite materials. Reference models without holes were first validated before introducing circular holes at varying distances from the crack front. The results reveal that strategically placed holes can reduce local stress concentrations and lower the J-integral values, mitigating the driving force behind crack propagation. These findings highlight the importance of geometric optimization and advanced simulation in improving damage tolerance and fracture resistance of composite structural components. Furthermore, the insights gained are particularly relevant to the aerospace industry, where fiber-reinforced polymer composites are increasingly used in aircraft structures due to their high strength-to-weight ratio and fatigue performance. Understanding fracture behavior under geometrical modifications enhances the structural reliability of such lightweight components under operational conditions. | composite materials, edge crack, J-integral, fracture mechanics, finite element analysis (FEA), crack propagation, stress distribution, geometric discontinuity | 2025 | 1 | 17 | 1-17 | 10.2478/fas-2025-0001 | Fatigue of Aircraft Structures |
| Mohamed Benguediab 1 Tayeb Kebir 2 Abdelkader Lahcene 1 Hichem Mebarki 3 Soumia Benguediab 4 Mustapha Benachour 5 | 1)Materials and Reactive Systems Laboratory, University of Sidi Bel Abbes, P.O. Box 89, Route de Tlemcen, Sidi Bell Abbes 22000, Algeria 2) Artificial Intelligence Laboratory for Mechanical and Civil Structures and Solid, Department of Mechanical Engineering, University Centre of Naama, P.O. Box 66, Naama 45000, Algeria 3) Center of Research in Mechanics (CRM), BP N73B, Freres Ferrad, Ain El Bey St., Constantine 25021, Algeria 4) Department of Civil Engineering and Hydraulic, University of Saida, P.O. Box 138, Cité Ennasr, Saida 20000, Algeria 5) Mechanical Systems & Materials Engineering Laboratory, Mechanical Engineering Department, Faculty of Technology, University of Tlemcen, P.O. Box 230, Chetouane, Tlemcen 13000, Algeria | ENERGETIC AND FRACTOGRAPHIC INVESTIGATION OF CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING | This study investigates fatigue crack propagation in aluminum alloy 2024-T351 under constantamplitude loading (CAL) and variable-amplitude loading (VAL), with a focus on energy parameters. The hysteretic energy dissipated at each load level (or per block) exhibits trends comparable to those observed under CAL conditions. At high propagation rates, both the dissipated hysteretic energy and the crack growth rate vary linearly, consistent with a propagation mechanism characterized by the formation of striations in each cycle. At lower propagation rates, the relationship between crack growth rate and dissipated energy per block follows a power-law form. The analysis is extended through quantitative microfractographic observations using scanning electron microscopy, which reveal the spatial distribution of key fractographic features and the mechanisms governing crack propagation. Based on these findings, an energy-based model is proposed that allows the replacement of load spectra with an equivalent constant-amplitude loading. | Fatigue, crack propagation, energy dissipated, constant amplitude, variable amplitude loading, striations, dimples | 2025 | 1 | 17 | 18-41 | 10.2478/fas-2025-0002 | Fatigue of Aircraft Structures |
| Grzegorz Socha Piotr Dąbrowski Jakub Kaczkowski | Łukasiewicz Research Network – Institute of Aviation, 110/114 Krakowska Ave., 02-256 Warsaw, Poland | EXPERIMENTAL INVESTIGATION AND FAILURE CRITERION DEVELOPMENT FOR CFR COMPOSITE TUBULAR SPECIMENS UNDER COMBINED AXIAL AND PRESSURE LOADING | Carbon-fiber-reinforced (CFR) composites in aircraft structures are subjected to complex, multiaxial loading conditions that may induce fatigue damage prior to final failure. To ensure structural safety, reliable failure criteria must be established for both undamaged and fatigueaffected materials. This study presents experimental investigations of tubular CFR composite specimens subjected to combined axial force and internal pressure, generating complex stress states in the thin-walled gage section. The specimens were loaded to failure along various stress paths, enabling construction of a failure surface in principal stress space. Three distinct failure modes were observed: resin matrix puncture, longitudinal cracking, and circumferential cracking with specimen separation. A probabilistic approach was introduced to account for the large scatter in experimental data, replacing deterministic failure stresses with stress values corresponding to specified survival probabilities. The results indicate that the maximum principal stress criterion, formulated in three-dimensional principal stress space with axes aligned to fiber directions, provides a suitable framework for the investigated composite. Incorporating probabilistic assessment improves reliability in predicting composite failure under complex loading. | Carbon Fiber Reinforced Polymer (CFRP) composites, Tubular specimens, Combined axial and pressure loading, Experimental investigation; Failure criterion, Multiaxial stress state, Mechanical behavior | 2025 | 1 | 17 | 42-57 | 10.2478/fas-2025-0003 | Fatigue of Aircraft Structures |
| Mengke Zhuang1 Nicolas O. Larrosa1 Julian D. Booker1 Christopher E.Truman1 | 1) School of Electrical, Electronic and Mechanical Engineering, Queens Building, University of Bristol, BS8 1TR, Bristol, UK | BAYESIAN-INFORMED FATIGUE LIFE PREDICTION FOR SHALLOW SHELL STRUCTURES | This study introduces a Bayesian-informed framework for fatigue life prediction in shallow shell structures. The methodology focuses on inferring the Equivalent Initial Flaw Size Distribution (EIFSD), a critical parameter for structural durability. Bayesian inference, combined with a Co-Kriging surrogate model, enables statistically robust predictions while accounting for uncertainties in material properties, geometry, and loading. The Dual Boundary Element Method (DBEM) is employed for crack propagation due to its efficiency and re-meshing-free modelling. To improve inference efficiency, an iterative parameter space narrowing strategy is proposed. Instead of exhaustively sampling the entire space, the method begins with coarse discretisation to locate high-probability EIFSD regions, then refines them adaptively. A numerical example involving a fuselage window under cabin pressure demonstrates the method. Surrogate models trained on DBEM-generated data significantly reduce computational cost. The proposed strategy achieves high-precision inference, with only 0.059% error in the inferred mean and 5.2% in standard deviation, while reducing CPU time by 52% compared to dense sampling. | Shallow Shell Structure; Equivalent Initial Flaw Size (EIFS); Dual Boundary Element Method (DBEM); Bayesian inference; Multi-fidelity model | 2024 | 1 | 16 | 1-15 | 10.2478/fas-2024-0001 | Fatigue of Aircraft Structures |
| Takao Okada1 Tomo Takeda1 Hisashi Kumazawa1 Toshiyuki Kasahara2 Sho Miyashita3 Koichi Yamada3 Kasumi Nagao3 Yuichiro Aoki3 | 1) Japan Aerospace Exploration Agency, 7-44-1 Jindaiji Higashi-machi, Chofu-shi, Tokyo 182-8522, Japan 2) Adecco Group Japan, 3-7-2 Sekitoukyuu Bld., Kasumigaseki, Chiyoda-ku, Tokyo, 100-0013, Japan 3) Former Japan Aerospace Exploration Agency | EFFECT OF THERMAL AND EXTERNAL LOAD ON MECHANICAL BEHAVIOUR ON CFRP/ALUMINIUM HYBRID JOINTS | JAXA has been conducted the research to evaluate the fatigue life up to form a certain size of fatigue crack in a CFRP/Aluminum hybrid joint. Thermal stress occurs in the hybrid joints during operation due to the difference of coefficient of thermal expansion between Aluminum and CFRP. In ICAF2023, we presented the experimental and numerical results for the hybrid joint under thermal cycles. In this study, the mechanically fastened hybrid joint specimens composed of two Aluminum plates and two CFRP plates are prepared. Most of the dimensions of the hybrid joint such as thickness, width of the plates and types and pitch of the fasteners and etc. are same as those evaluated in the previous research. The cyclic thermal and external loads are simultaneously applied to the hybrid joint and stress and strain on the Aluminum plate are evaluated experimentally and numerically. From the behavior of the elastic strain, which is the total strain minus the thermal strain, it is shown that when thermal load and external load are coupled, the hysteresis loop becomes larger than when only the external load is repeatedly applied. In addition, it is shown that the strain and stress around the fastener holes in the top row through the load direction are high, and this could be a critical area for fatigue failure. | Hybrid joints, Thermal and external load, Hysteresis loop, Fatigue fracture, Finite element analysis | 2024 | 1 | 16 | 16-28 | 10.2478/fas-2024-0002 | Fatigue of Aircraft Structures |
| Nikolai Kashaev1 Tim Mohr1 Sören Keller1 Uceu Fuad Hasan Suhuddin1 Benjamin Klusemann1,2 Falk Dorn1 Volker Ventzke1 | 1) Institute of Material and Process Design, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, D-21502 Geesthacht, Germany 2) Institute for Production Technology and Systems, Leuphana University of Lüneburg, Universitätsallee 1, D-21335 Lüneburg, Germany | ON THE APPLICATION OF LASER SHOCK PEENING AS A MANUFACTURING AND REPAIR PROCESS TO IMPROVE THE FATIGUE PERFORMANCE OF REFILL FRICTION STIR SPOT-WELDED AA2024-T3 JOINTS | The refill friction stir spot welding (refill FSSW) process is an innovative solid-state spot-welding method, which has evolved from the concept of friction stir welding. Compared to riveting, the process has the advantage of avoiding stress concentration by eliminating holes. In addition, weight can be saved compared to riveting as no additional material is needed. However, the fatigue strength of refill FSSW joints under cyclic loading is still not satisfactory. To address this challenge, laser shock peening (LSP) is investigated as an innovative residual stress engineering technique to improve the fatigue performance of refill FSSW AA2024-T3 joints. Two application scenarios are investigated, one investigating the LSP technique as a complementary manufacturing process to the refill FSSW technology, and the other investigating the LSP technique as a repair process for damaged joints. The fatigue test results showed that the application of the LSP treatment can significantly improve the fatigue behaviour of the refill FSSW overlap joints. In terms of Basquin fatigue strength, the LSP treatment resulted in an improvement by a factor of 1.51 and 2.82 for the one- and two-sided LSP-treated specimens, respectively. The life of specimens with refill FSSW joints that had been specifically pre-damaged by stopping the fatigue test at approximately 51%, 75% and 83% of the number of cycles to the Basquin fatigue strength, applying LSP treatment and continuing the fatigue test was also significantly extended. The results of this study show that LSP is a very effective technique for significantly extending the fatigue life of refill FSSW joints. Therefore, the combination of these two manufacturing processes, refill FSSW and LSP, represents a promising technology for industrial companies that require high fatigue performance for their structural components. | fatigue crack, refill friction stir spot-welding, laser shock peening, residual stress, fatigue life extension | 2024 | 1 | 16 | 29-44 | 10.2478/fas-2024-0003 | Fatigue of Aircraft Structures |
| Benoît Morlet1 Fabrice Congourdeau1 Guy Sola2 Dominique Martini1 Alban Robin1 Vincent Jacques1 | 1) DASSAULT-AVIATION Saint-Cloud 78, quai Marcel Dassault, 92552 Saint-Cloud Cedex, France 2) DASSAULT-AVIATION Mérignac 54 avenue Marcel Dassault, 33701 Mérignac Cedex, France | RESIDUAL STRENGTH ANALYSIS OF A COMPOSITE STIFFENED PANEL AFTER A STIFFENER DEBONDING USING AN INDUSTRIAL NUMERICAL DAMAGE MODEL | The increasing demand for greener aviation technology has driven the adoption of advanced composite materials in aircraft structures, offering significant weight saving and fuel efficiency improvements. Wing structures made of torsion boxes composed of stiffened panels have shown over the decades the benefits provided by composite technology, which is able to adapt the material properties to the structural constraints to which the structure is subjected. A convenient manufacturing technology for stiffened panels consists of co-bonding stiffeners on pre-cured skin. On these structures, the certification authorities require the demonstration of the residual strength at limit load of the panel with a disbonded stiffener. This is typically a post-buckling problem where the complete failure of the panel is due to a secondary buckling mode or the failure of adjacent stiffeners due to the combination of compressive and tearing loads, the larger buckled panel bay generating pull out loads on the adjacent stiffeners. This demonstration is classically performed by tests on large stiffened panels. In a composite wing box where geometrical parameters and loading modes can vary significantly from one zone to another, the numerical simulation can bring significant benefits to reduce the number of tests. This article presents a numerical damage model able to predict the damage and disbond of a co-bonded stiffener and applicable to a large aircraft structural model that can be integrated into a post-buckling simulation. As a validation case, this model has been applied to a multi stiffened composite panel where a central stiffener has been disbonded. The simulation results gave accurate predictions for the buckling loads and modes as well as for the appearance of damages on stiffeners until the panel failure. | Composite, damage model, stiffened panel, post-bucking | 2024 | 1 | 16 | 45-56 | 10.2478/fas-2024-0004 | Fatigue of Aircraft Structures |
| Marcin Praski 1,2 Piotr Kowalczyk 2 Radosław Szumowski 2 Karolina Stankiewicz 2 Andrzej Leski 1, 2 | 1) Military University of Technology, 2 gen. S. Kaliskiego St., 00-908 Warsaw, Poland 2) Łukasiewicz Research Network – Institute of Aviation, 110/114 Krakowska Ave., 02-256 Warsaw, Poland | FEM ANALYSIS OF RESIDUAL STRESSES IN WELDED ALUMINUM AND POLYAMIDE 6 | Thermoplastic composites enable weldable, recyclable aircraft structures, but thermal mismatch between metals and polymers can introduce detrimental residual stresses. This study develops a finite element method (FEM) framework to predict residual stress fields in resistance-welded joints between aluminum 7075 and carbon-fiber-reinforced polyamide 6 (PA6). Transient thermal analyses with multilinear, temperature-dependent properties were coupled to mechanical analyses; contact conditions transitioned from frictional to bonded at PA6 melting. Three thermal cycles (20°C→220°C→20°C, 20°C→240°C→20°C, 20°C→260°C→20°C) were examined to assess peak-temperature effects. The simulations show stress contours that decay with distance from the bond and reveal pronounced peaks in both normal and shear components at weld edges, consistent with shear-lag theory. Within the bonded interior, average stresses are relatively low, whereas edge concentrations identify likely sites for debonding or delamination initiation. The magnitude of residual stresses increases with thermal gradient, underscoring the need for parameter control during welding. The FEM outputs will be validated against uniaxial tension and three-point bending tests on welded specimens, with future work quantifying fatigue-life reduction under combined thermal and mechanical cycling. The results highlight mitigation priorities for bonded repairs and hybrid aerospace structures, including process-curve tuning (current/pressure/cooling) and edge-region design measures. | thermal stress, fem, composite, thermoplastic composite, polyamide 6, residual stress, NDT | 2024 | 1 | 16 | 57-74 | 10.2478/fas-2024-0005 | Fatigue of Aircraft Structures |
| Rando Tungga Dewa 1 M. Ircham Atami 1 Anang Setiawan 1 Fattah Maulana 1 Wafiqni 2 | 1) Department of Mechanical Engineering, Republic of Indonesia Defense University, IPSC Area, Bogor 16810, Indonesia 2) Division of Design and Structural Analysis, Indonesian Aerospace, Bandung 40174, Indonesia | FATIGUE LIFE ESTIMATION OF THE CRITICAL WING STRUCTURE IN A NEW-GENERATION STOL AIRCRAFT | The lower wing section of an aircraft is considered particularly vulnerable to fatigue failure due to the presence of inspection holes, which create stress concentrations and increase local stress in the surrounding material. This study estimates the fatigue life of the lower wing structure, including rivet holes around the inspection openings, in a new-generation Indonesian short takeoff and landing (STOL) aircraft under cyclic flight loads. Fatigue assessment was conducted in five stages: (1) development of a 3D design model of the lower wing skin; (2) stress analysis of the skin without rivet holes, using finite element analysis (FEA), to identify critical areas around the inspection hole; (3) stress analysis of the skin with rivet holes in these critical areas; (4) compilation of a stress spectrum from flight test data; and (5) fatigue life estimation using the cumulative damage method with the application of a scatter factor. The analysis results indicate a maximum fatigue life of 67,750 flight cycles for rivet holes in the lower wing skin, exceeding the industry target of 30,000 cycles. However, when a scatter factor is applied, the maximum fatigue life is reduced to 13,550 flight cycles, establishing the required inspection threshold for the STOL aircraft. | Palmgren-miner rule, Fatigue life, Cumulative damage, Load spectrum, MSC. Patran/Nastran, Center wing box | 2024 | 1 | 16 | 75-88 | 10.2478/fas-2024-0006 | Fatigue of Aircraft Structures |
| Michea Ferrari 1 Juan D. Ocampo 2 Samson Taylor 1 Viola Ferrari 1 Dimitri Wahlen 1 Mattia Lüchinger 1 Mirco Figliolino 3 | 1) RUAG AG, 175, Seetalstrasse, 6032 Emmen, Switzerland 2) St. Mary’s University, 1 Camino Santa Maria, San Antonio, TX 78228, United States of America 3) Armasuisse, Guisanpl. 1, 3003 Bern, Switzerland | OPTIMIZING INSPECTION INTERVALS THROUGH RISK EVALUATION IN AIRCRAFT STRUCTURES | As aircraft fleets age, maintaining operational readiness at an affordable cost becomes increasingly challenging. This is largely due to the rise in Preventive Maintenance Task Requirements (PMTRs) outlined in the Aircraft Maintenance Program (AMP). While aging aircraft may require more frequent inspections, leveraging data from prior inspections enables the optimization of inspection intervals based on risk, ensuring cost efficiency by minimizing unnecessary downtime, while maintaining the required safety level. The primary objective of the AMP is to ensure the airworthiness and operational readiness of an aircraft system throughout their service life. To achieve this, it is essential to establish an acceptable level of risk as a basis for determining optimal PMTR recurrence. The SMART|DT tool, developed with FAA funding, provides a robust framework for conducting risk assessments of aircraft structures using Probabilistic Damage Tolerance Analysis (PDTA), which effectively assesses and manages the risk of structural failure. During the sustainment phase of the Swiss Air Force F/A 18 fleet, data-driven analyses within SMART|DT, and other tailored statistical tools, were performed to evaluate the risks associated with various PMTR intervals. This paper will explain the methodology applied to both Safe-Life and Damage-Tolerance structures, with real-world applications to demonstrate how inspection intervals can be optimized. By doing so, PMTR recurrence can be fine-tuned to enhance aircraft readiness and program affordability while maintaining an acceptable level of safety. | Safe life, damage tolerance, risk assessment, SMART|DT | 2024 | 1 | 16 | 89-101 | 10.2478/fas-2024-0007 | Fatigue of Aircraft Structures |
| Benjamin Delpuech1 Maxime Nutte2 Vincent Jacques3 Benoit Morlet3 | 1) DASSAULT AVIATION, 54 Avenue Marcel Dassault, 33700 Mérignac, France 2) DMAS – ONERA, Université Paris Saclay, 92320 Châtillon, France 3) DASSAULT AVIATION, 78, quai Marcel-Dassault, 92500 Saint-Cloud, France | DEVELOPMENT OF A ROBUST MULTIAXIAL FATIGUE MODEL FOR A/C METALLIC ASSEMBLIES IN AN INDUSTRIAL CONTEXT | In a context of growing importance of mass reduction and reliability of structures towards greener aircrafts, fatigue of metallic materials is a key issue in the structural optimization. The process used by aeronautic industrials to compute the fatigue life is often based on a large empirical experience and meets a need for efficiency in their application, requiring a compromise between accuracy and ease of use. According to legacy crack initiation methodologies, lifetime computation is based on the analysis of elastic stress fields, calculated analytically or by Finite Element Method. Evaluation of lifetime is calibrated on elementary tests, mainly uniaxial, with geometric specificity (bone, hole, notch…). One of the limits of this approach appears when parts are subjected to multi-axial loads. Nowadays, these particular stress states are justified by conservative approaches to ensure flight safety and by tests on full-scale aircrafts. Whether for the operational maintenance or the structural optimization of new aircrafts, it is intended to enhance crack initiation methodologies, taking into account multiaxiality of loads, stress gradient effects, and complex material behaviours. Dassault-Aviation implements a crack initiation lifetime computation based on a local approach. These developments go hand in hand with a PhD (Nutte, 2023) on a multiaxial fatigue criterion in order to predict crack initiation in metallic assemblies. This work was supported by an innovative dedicated test campaign. The identification of material’s parameters is based on uniaxial and multi-axial mechanical tests, specifically designed to calibrate these models. Then, novel geometry of specimen for bolted assemblies, facilitating various biaxial non-proportional loadings, is used to evaluate the methodology. Also, multiaxial fatigue models require a precise assessment of the local mechanical fields to which the structure is subjected. For this, a finite element analysis must be conducted with a level of complexity associated with the level of accuracy targeted. The material constitutive equations used in the finite element analysis are therefore at the heart of these fatigue substantiation approaches. Applications to complex aeronautical structures such as massive 3D parts or assembly by fastener will highlight the benefits and perspectives for this local fatigue approach. It will require the use of multi-scale data science. | Fatigue, Local, Junction, Multiaxial, Test | 2024 | 1 | 16 | 102-118 | 10.2478/fas-2024-0008 | Fatigue of Aircraft Structures |
| Yuhang Pan 1 Zahra Sharif Khodaei 1 M.H. Aliabadi 1 | 1) City and Guilds Building, Department of Aeronautics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK | BASELINE-FREE DETECTION OF PROGRESSIVE FATIGUE DAMAGE USING NONLINEAR ULTRASONIC GUIDED WAVES | Detecting fatigue-induced progressive damage under varying environmental conditions remains a major challenge in structural health monitoring (SHM). This study investigates a baseline-free nonlinear guided wave method, which extracts nonlinear parameters to detect fatigue cracks without requiring baseline signals from the pristine state. The method demonstrates reliable detection of cracks around 3 mm in size, with the nonlinear parameter serving as a sensitive indicator of damage initiation and growth. Its independence from baseline signals enhances practicality for in-service monitoring applications. However, experimental results reveal that the method’s performance is sensitive to temperature variations, with irregular responses observed at different temperatures, which may affect detection consistency. These findings highlight both the potential and the limitations of nonlinear guided wave methods, underscoring the need for temperature compensation strategies to improve their robustness under variable environmental conditions. Overall, the proposed approach contributes to advancing baseline-free SHM techniques by offering a viable solution for progressive crack detection in realistic service environment. | Progressive damage, Structural health monitoring (SHM), Temperature variations, Nonlinear guided wave | 2024 | 1 | 16 | 119-130 | 10.2478/fas-2024-0009 | Fatigue of Aircraft Structures |
| Lilin Tian 1 Jun Wang 1 Chaofeng Zhang 1 Yuchao Guo 1 Liang Chang 1 | 1) National Key Laboratory of Strength and Structural Integrity, Aircraft Strength, Research Institute of China, 710065, Xi’an, China | RANDOM VIBRATION FATIGUE LIFE ANALYSIS OF AEROENGINE BOLTS USING THE FREQUENCY-DOMAIN METHOD | Bolt connections are widely used in aircraft engines due to their advantages of high stiffness, low weight, and ease of assembly and disassembly. However, they are subjected to complex stress states in service, including high preloads, combustion-induced forces, and random vibrations, which may lead to fatigue failure. Since the fatigue performance of bolts directly affects the reliability of engines and their fuel accessories, accurate fatigue life estimation is essential for safe design. This study proposes a frequency-domain method for evaluating the random vibration fatigue life of bolts in aeroengine fuel accessories. A detailed finite element model of the bolted connection was established, with excitation boundary conditions defined by the assembly configuration. Modal, frequency response, and random response analyses were performed to obtain the stress power spectral density (PSD) of the bolts. The Dirlik method, combined with the material’s S–N curve, was then applied to estimate fatigue life under broadband and narrowband vibration excitation. Results show that bolts in the Y-direction experience the highest RMS stresses, leading to the shortest fatigue life – approximately 4.44 hours under critical loading conditions – which does not meet design requirements. The proposed method enables rapid evaluation of bolt fatigue life under random vibration environments, providing a practical tool to support bolt selection and design optimization in aeroengine applications. | bolt fatigue; Dirlik method; random vibration; fatigue life prediction | 2024 | 1 | 16 | 147-160 | 10.2478/fas-2024-0010 | Fatigue of Aircraft Structures |
| Rob Plaskitt 1 Chris Wynn-Jones 1 Andrew Halfpenny 1 | 1) Hottinger Bruel & Kjaer Ltd, United Kingdom | WEIBULL OR LOGNORMAL DISTRIBUTION TO CHARACTERIZE FATIGUE LIFE SCATTER — WHICH IS MORE SUITABLE? — CONTINUED | This paper describes a study to determine whether fatigue test life scatter is best characterised by a Weibull or lognormal statistical distribution for a high strength steel used for landing gear structures. It is a response to “Face 2” of the ICAF 2017 Plantema Memorial Lecture and 2019 follow-up paper with the question; “Weibull or Lognormal Distributions to Characterize Fatigue Life Scatter?” These concluded that a Weibull distribution appears to be more suitable than a lognormal distribution for statistical modelling of fatigue life scatter to define an allowable service life at a specific probability of failure. Those studies used a homogenous dataset of 18 fatigue tests, and a non-homogenous dataset of 86 fatigue tests from a variety of sources. This paper reviewed HBK historical fatigue tests to identify a homogeneous dataset of 371 fatigue tests for a high strength steel used for landing gear structures. Weibull and lognormal statistical modelling of this dataset concluded that its fatigue life scatter is best characterized by the lognormal distribution. | Fatigue life scatter, Weibull, lognormal, statistical distributions | 2024 | 1 | 16 | 131-146 | 10.2478/fas-2024-0011 | Fatigue of Aircraft Structures |
| Miłosz Sobociński 1 Piotr Synaszko 1 Krzysztof Dragan 1 Jakub Kotowski 1 | 1) Air Force Institute of Technology, 6 Księcia Bolesława St., 01-494 Warsaw, Poland | BUILDING A CAD-NATIVE DIGITAL TWIN FOR NDT AND PLM: WORKFLOW, TOOLS, AND CASE STUDY | Digital twins (DTs) can connect inspection data with product models to support safer, more efficient lifecycle decisions. This paper proposes a CAD-native workflow for implementing a digital twin that visualizes and manages non-destructive testing (NDT) results directly on a 3D model. The method supports over-the-surface data (ultrasonic C-scans, UT) via UV mapping and projected images (thermography, TT) via planar projection, both executed in Siemens NX with custom macros for point localization and on-surface measurement. We validate the approach on a bottom nacelle panel from a Honeywell HTF7000 turbofan engine, acquired via 3D scanning and reverse engineering. The resulting digital twin preserves a persistent spatial link between inspection images and geometry, enables remote sizing and review, and centralizes result management in the CAD environment for PLM use cases (e.g., defect history, trend analysis). Timelines indicate higher initial effort but reduced on-site workload and travel for qualified inspectors thereafter. Limitations include large file sizes when storing geometry and multiple images in a single model; we outline a lightweight distribution strategy and future automation/VR enhancements. The findings demonstrate the feasibility and practical value of CAD-resident digital twins for NDT visualization, remote evaluation, and product lifecycle management. | Digital Twin; 3D NDT; CAD; 3D thermography and ultrasonic testing; defects database; Product Lifecycle Management | 2024 | 1 | 16 | 161-187 | 10.2478/fas-2024-0012 | Fatigue of Aircraft Structures |
| Tayeb Kebir 1,2 Mohamed Belhamiani 3 Ahmed Amine Daikh 1,4 Mohamed Benguediab 2 Mustapha Benachour 5 | 1) Artificial Intelligence Laboratory for Mechanical and Civil Structures and Soil, Department of Mechanical Engineering, Institute of Technology, University Center of Naama, Naama 45000, Algeria. 2) Laboratory of Materials and Reactive Systems, University of Sidi Bel Abbes, Algeria. 3) Smart Structures Laboratory, Department of Mechanical Engineering, Belbachir Belhadj University of Ain Temouchent, 46000 Algeria. 4) Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli B.P. 305, R.P. 29000 Mascara, Algeria. 5) Mechanical Systems & Materials Engineering Laboratory, Mechanical Engineering Department, Faculty of Technology, University of Tlemcen, BP 230 – 13000, Tlemcen, Algeria | INVESTIGATING THE EFFECTS OF CRACK ORIENTATION AND DEFECTS ON PIPELINE FATIGUE LIFE THROUGH FINITE ELEMENT ANALYSIS | In response to the steady rise in global demand for energy resources such as gas and oil, there is a pressing need to enhance the efficiency and safety of pipeline transportation systems. These systems, integral for transferring vast amounts of energy, must operate under increasingly higher pressures and larger diameters without compromising reliability. This study focuses on utilizing finite element analysis (FEA) to investigate the influence of crack orientation and the presence of defects on the fatigue life of pipelines. By simulating internal pressure scenarios and examining various defect characteristics with the AFGROW software, this research applies damage tolerance principles to offer insights into the fatigue behavior of pipelines. The findings can be applied to extend the operational life and ensure the integrity of these critical infrastructures, thereby supporting the sustainable and safe transport of energy resources. | pressure equipment, pipelines, fatigue, safety, reliability, loading | 2023 | 1 | 15 | 1-21 | 10.2478/fas-2023-0001 | Fatigue of Aircraft Structures |
| Mateusz Kopec 1 Dominik Kukla 1 Mirosław Wyszkowski 1 Zbigniew L. Kowalewski 1 | 1) Institute of Fundamental Technological Research, Polish Academy of Sciences, 5b Pawińskiego Str., 02-106 Warsaw, Poland | HIGH-TEMPERATURE FATIGUE TESTING OF TURBINE BLADES | This paper evaluates the efficacy of a patented grip for high-temperature fatigue testing by establishing the S-N curve for full-scale nickel-based turbine blades under simulated environmental conditions. Initially, a bending test assessed the stress-displacement characteristics of the component. This was followed by a series of fatigue tests at 950°C, using cyclic bending with force amplitudes from 5.2 kN to 6.6 kN and a constant frequency of 10 Hz. The setup, integrating the grip into a standard testing machine, proved effective for high-temperature tests and successfully determined the service life of full-scale components. | fatigue, high temperature, turbine blade, full-scale fatigue test | 2023 | 1 | 15 | 22-27 | 10.2478/fas-2023-0002 | Fatigue of Aircraft Structures |
| Krzysztof Stanisław Szafran 1 Łukasz Andrzej Jeziorek 2 | 1) Łukasiewicz Research Network – Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland. 2) Łukasiewicz Research Network – Institute of Aviation, EDC, al. Krakowska 110/114, 02-256 Warsaw, Poland | USING OWN ALGORITHMS TO INCREASE THE QUALITY AND FATIGUE RESISTANCE OF FDM PRINTING FOR USE IN DRONES AND SMALL AIRCRAFT | The present article discusses the three-dimensional (3D) printing process in the fused deposition modeling (FDM) or the fused filament fabrication (FFF) technique using the author’s own philosophy of shaping the printing head path. The main requirements are the possibility of eliminating supports and reducing or even eliminating the need for the mechanical processing of 3D prints before their final assembly. The presented methodology was implemented in a computer program written by the author and was used to print typical parts used in aviation. Individual methods of shaping parts typical for the construction of small flying models, such as wings and fuselages, and methods of strengthening and connecting them have been discussed. The proposed solutions are illustrated with photos of readymade prints. This article also discusses the issues that printing high-quality parts may encounter and how to avoid them. Some attention has also been paid to the materials used for printing and their suitability in the construction of aircraft and their fatigue strength. | FDM, FFF, 3D printing, PLA, ABS, polymer, fatigue | 2023 | 1 | 15 | 28-43 | 10.2478/fas-2023-0003 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 | 1) Department of Aerospace Engineering, Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, al. Powstańców Warszawy 12, 35-959 Rzeszów | SOME COMMENTS CONCERNING THE PREPARATION OF AND FATIGUE TESTING OF THE AIRCRAFT’S CABLE-CONTROL SYSTEM | The currently accepted rules that are applied to the aircraft cable-control systems’ operational use are based on the reactive maintenance idea and the comparative tests, inspections, and diagnostics performed at the mandatory intervals. Fatigue tests of the aviation cables are commonly conducted by bending in the range of 90 with constant load. Aircraft cable-control systems are subject to a number of random loads and deformations. Additionally, forces and their values are modified by the wear and tear of cable-pulley raceways, elastic deformations, and changes caused by temperature. The actual values of tension of aviation cable-control systems are relatively low, and bending usually does not exceed the maximum of 35. Moreover, the forces characteristic of the control cables are nonlinear functions of the control surface deflection. This means that the typical fatigue tests we employ help with only comparative estimations and acceptance tests. It is not possible to estimate the operational durability of the systems and forecast inspections and diagnoses intervals based on the mentioned results. The present article utilizes the operational profiles of selected aircraft categories to determine the stochastic load-related deflection spectra for the preparation of cable fatigue-testing programs. Operation profiles are built considering a group of aircraft belonging to the same category, performing similar missions, for example, training missions, photogrammetric missions, aircraft towing, e.q., and having a similar share in the total resource. The special stands for the selected cable fatigue tests have been proposed. The cable test stand ensures the real stochastic loads for the cable use and other actual conditions of load. The proposed stand enables the simultaneous testing of more than one cable at different deformation parameters, for example, wrap angles. The results of the proposed method and tests can be used to estimate the operational durability of aviation-control systems as well as for inspection and diagnosis intervals as well. | aviation cable control systems, cables and ropes fatigue tests, inspection intervals assessment, load spectrum, fatigue life | 2023 | 1 | 15 | 44-57 | 10.2478/fas-2023-0004 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska1 Paweł Żuk2 Michał Bujak2 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland. 2) GE Aerospace Poland, Al. Krakowska 110/114, 02-256 Warsaw, Poland | X-RAY DIFFRACTION MEASUREMENTS FOR INCONEL 718 ALLOY ELEMENTS CREATED BY INCREMENTAL METHODS | The work presented is the result of the implementation of diffraction measurements: phase composition and stresses resulting from additive manufacturing process of nickel superalloy Inconel 718 components print. With the help of diffraction methodologies, the key parameters from the point of view of the quality of prints and their strength were determined. The existence of individual phases in the material after printing was demonstrated, and the surface variation of the stress values was presented, showing its dependence on the geometry of the printed part – measurements were made at various points on the surface of samples with different geometries. In addition, the variation of the stress level was shown depending on the distance of the measurement point from the build platform on which the additive manufacturing process was carried out. Components were printed on the surface of a single build plate in order to study the effect of printing differently oriented samples with respect to the platform geometry, as well as the mutual effect of the temperature of samples printed first on the stress state of elements printed in subsequent steps of the procedure, and the effect of the temperature of elements printed later on the rate of temperature decrease, and consequently on the stress state, of elements printed first. | diffraction, stress, additive manufacturing, DMLM, Inconel 718 | 2023 | 1 | 15 | 58-89 | 10.2478/fas-2023-0005 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Maciej Malicki 1 Anna Trykowska 1 Grzegorz Moneta 1 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | DEVELOPMENT OF DIFFRACTIORESEARCH METHODOLOGIES FOR MEDILOY S-CO ALLOY SPECIMENTS MADE USING LPBF ADDITIVE MANUFACTURING | This study focuses on the application and improvement of diffraction measurement methodologies for the optimization of manufacturing parameters of CoCr alloy components made by additive manufacturing (AM) – particularly for Mediloy S-Co alloy specimens made using Laser Powder Bed Fusion (LPBF) additive manufacturing. We measured the phase composition of specimens obtained in AM processes, the measurement of residual stresses resulting from the manufacture of these printed parts, as well as the effectiveness of stress relaxation through the use of heat treatments dedicated to this type of material. Findings reveal several insights into how printing strategies affect the porosity and residual stresses in additive manufacturing. Specimens with higher porosity, particularly those created using specific strategies that resulted in lower energy densities, exhibited lower residual stresses. Notably, printing direction and energy density were found to significantly affect the mechanical stresses within the specimens, with directional choices playing a critical role in the final properties of the parts. Additionally, our findings underscore the complex relationship between various printing parameters and the development of mechanical stresses, highlighting the impact of adjustments in printing strategy on the properties of printed components. | diffraction, phase analysis, stress, additive manufacturing, selective laser melting (SLM), Mediloy S-Co, Laser Powder Bed Fusion (LPBF) | 2023 | 1 | 15 | 90-114 | 10.2478/fas-2023-0006 | Fatigue of Aircraft Structures |
| Aun Haider 1 | 1) Institute of Aeronautics and Avionics, Air University Islamabad, E-9/4 E-9, Islamabad, Islamabad Capital Territory 44000, Pakistan | A COMPARISON OF FREE AND MAPPED MESHES FOR STATIC STRUCTURAL ANALYSIS | This study addresses the challenge faced by Finite Element Analysts when choosing between free and mapped meshes, especially in terms of convergence stability and solution accuracy. The investigation focuses on 3D solid models under static structural loading, analyzed using Ansys® and MSC Patran®. Both free and mapped mesh types, employing equivalent 3D solid elements, are used to assess an aircraft structural component under design load conditions, with fixed boundaries. For free meshes, Tet10 elements in Patran (equivalent to Solid 72 in Ansys) are used, whereas for mapped meshes, CPENTA / CHEXA elements in Patran (equivalent to Wed6 / Hex8 in Ansys) are employed. Mesh convergence studies ensure that discretization does not affect the numerical solution. Notably, a significant stress increase is observed with successive refinement of free meshes, while mapped meshes achieve mesh independence at coarser refinement levels. Comparison of fringe plots indicates the same location for maximum deformation and equivalent stress in both free and mapped mesh models. The findings demonstrate that free meshes tend to underpredict maximum deformation and equivalent stress compared to mapped meshes, with both meshes showing deformation and stress at consistent locations. The findings underscore the importance of carefully choosing the appropriate mesh type, particularly when analyzing critical structural components, to ensure reliability and accuracy in FEA simulations. | mesh convergence, mesh independence, discretization scheme, Finite Element Analysis, FE Software | 2023 | 1 | 15 | 115-132 | 10.2478/fas-2023-0007 | Fatigue of Aircraft Structures |
| Zbigniew Skorupka 1 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | DYNAMIC TESTING AND FATIGUE ANALYSIS OF THE I-31P NOSE LANDING GEAR | The landing gear is a critical safety component of any aircraft, playing a key role in managing the significant loads experienced during landing and ground maneuvers. In the case of the I-31P aircraft, a redesign of the I-23 landing gear system, required comprehensive testing to validate its performance, after change of landing gear parts manufacturer and minor updates to materials and technologies. This study focuses on the dynamic testing of the I-31P nose landing gear (NLG), particularly to assess its energy dissipation and fatigue resistance under operational conditions. Dynamic tests, performed in accordance with CS-23 standards, utilized strain gauges to monitor potential stress concentrations, especially on the half-fork design. Results demonstrated that the I-31P nose landing gear meets the required safety standards, with key performance metrics such as deflection and load factors within acceptable limits. The findings also highlighted the importance of continued monitoring for potential fatigue issues, offering valuable insights for future design enhancements. | I-31P, nose landing gear (NLG), laboratory tests, dynamic testing | 2023 | 1 | 15 | 133-145 | 10.2478/fas-2023-0008 | Fatigue of Aircraft Structures |
| Michał Siniarski 1 Piotr Synaszko 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, ul. Księcia Bolesława 6, 01-494 Warsaw, Poland | DEVELOPMENT OF AN OPEN-SOURCE ROBOTIC NDT SOLUTION FOR AUTOMATED COMPOSITE REPAIR TESTING | Non-destructive testing (NDT) plays an important role in aircraft maintenance and repair processes, ensuring the structural integrity necessary for safe operation. The paper presents the design and evaluation of an animated, low-cost robotic NDT system tailored for inspecting composite bonding agents. The system integrates commercially available components, including a three-degree-of-freedom robotic arm and a Raspberry Pi 4B, managed by custom Python software with a user-friendly graphical interface. Mechanical Impedance Analysis (MIA) and Eddy Current Testing (ET) methods were employed to assess the system’s performance on representative test specimens. Results indicate that the system delivers reliable and accurate measurements comparable to commercial tools like the MAUS V, while offering simplicity and modularity. Limitations such as scanning speed and handling of complex geometries are acknowledged, with potential solutions proposed for future enhancement. The system provides an affordable and customizable alternative for NDT automation in the aerospace industry. | non-destructive testing, robotics, automation, Eddy Current Testing, Mechanical Impedance Analysis, Python, airworthiness | 2023 | 1 | 15 | 146-154 | 10.2478/fas-2023-0009 | Fatigue of Aircraft Structures |
| Piotr Reymer1,2 Kamil Kowalczyk1 Marta Baran1 Dominik Nowakowski1 Michał Dziendzikowski1 Andrzej Leski2,3 | 1) Air Force Institute of Technology, Ks. Bolesława 6, 01-494 Warsaw, Poland 2) Military University of Technology, gen. Sylwestra Kaliskiego 2, 00 -908 Warsaw, Poland 3) Lukasiewicz Research Network – Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | CRACK PROPAGATION TESTS FOR LOAD SEQUENCES DEVELOPED USING DIFFERENT FLIGHT PARAMETERS OF A TRAINER AIRCRAFT | Military aircraft are subjected to highly variable and unpredictable loads due to diverse mission profiles, armament configurations, and individual piloting styles. This variability complicates the definition of precise load spectra, particularly in cases where data loss occurs due to Flight Data Recorder (FDR) malfunctions or data mishandling. This paper investigates the use of different flight parameters, such as load factor (nz), barometric height (Hb), and horizontal velocity (Vp), to define load sequences for the PZL-130 “Orlik” TC-II military trainer aircraft. These sequences were then used to evaluate crack propagation using Compact Tension (CT) specimens. The results show that the incorporation of additional flight parameters improves the accuracy of crack propagation predictions when compared to direct strain measurements. This study highlights the potential of using available flight data to develop reliable load spectra for fatigue life estimation in military aircraft, even when direct load measurements are not financially feasible. | fatigue crack propagation, flight parameters, load sequence | 2023 | 1 | 15 | 155-165 | 10.2478/fas-2023-0010 | Fatigue of Aircraft Structures |
| Patryk Ciężak1 Loudres Vazquez-Gomez 2 Luca Mattarozzi 2 Alessandro Benedetti 2 Jakub Kotowski3 Piotr Synaszko3 Krzysztof Dragan 3 Dominik Głowacki 4 Konrad Wawryn 5 | 1) Military University of Technology, gen. S. Kaliskiego 2, 00-908 Warsaw, Poland 2) National Research Council – Institute of Condensed Matter Chemistry and Technologies for Energy, Corso Stati Uniti 4, 35127 Padova, Italy 3) Air Force Institute of Technology, Księcia Bolesława 6, 01-494 Warsaw, Poland 4) Warsaw University of Technology, plac Politechniki 1, 00-661 Warsaw, Poland 5) UMF – Unique Model Factory, Poland | USING CORROSION HEALTH MONITORING SYSTEMS TO DETECT CORROSION: REAL-TIME MONITORING TO MAINTAIN THE INTEGRITY OF THE STRUCTURE | This study investigates the use of Corrosion Health Monitoring (CHM) systems to detect and manage corrosion in aviation environments, with a specific focus on enclosed areas within aircraft structures. Corrosion poses significant risks to airport facilities and aircraft, and CHM systems offer real-time monitoring and data-driven approaches for proactive corrosion management. Through case studies conducted at two different test sites, the effectiveness of deploying advanced sensors was demonstrated in identifying corrosion-prone areas, optimizing maintenance schedules, and enhancing safety and structural integrity. The study highlights the variability in corrosion rates between openair and enclosed conditions, emphasizing the need for tailored prevention strategies. It also discusses the challenges of integrating CHM systems into existing maintenance practices and airport infrastructure, addressing issues such as sensor placement, data management, and regulatory compliance, and outlines future directions for R&D in this critical area. By incorporating CHM systems, the aviation industry can transition from reactive to predictive maintenance, improving the reliability and lifespan of assets while reducing costs. | corrosion, CHM, SHM, aviation, aircraft, structure integrity | 2023 | 1 | 15 | 166-182 | 10.2478/fas-2023-0011 | Fatigue of Aircraft Structures |
| Hassina Madjour 1 Hanane Zermane 1 Djemaa Rahmouni 1 Mohammed Djamel Mouss 1 | 1) Laboratory of Automation and Manufacturing, Department of Industrial Engineering, University of Batna 2, Batna, Algeria | COMPARATIVE ANALYSIS OF DEEP LEARNING AND DECISION TREE APPROACHES FOR PREDICTING AIRCRAFT ENGINE REMAINING USEFUL LIFE | Accurate prediction of Remaining Useful Life (RUL) is crucial for Prognostics and Health Management (PHM), particularly in predictive maintenance strategies aimed at ensuring the reliability of industrial systems. This study compares two approaches for RUL prediction of aircraft engines: a deep learning-based one-dimensional Convolutional Neural Network (CNN-1D) and a traditional Decision Tree (DT) algorithm, using data from the C-MAPSS dataset. The results show that the CNN-1D model significantly outperforms the DT model, achieving a Root Mean Square Error (RMSE) of 21.44 on the training set and 27.12 on the test set, compared to the DT model’s RMSE of 23.83 and 28.93, respectively. These findings highlight the superior capability of deep learning techniques in RUL estimation, underscoring their importance in PHM and predictive maintenance applications. | Remaining Useful Life, Deep Learning, Convolution Neural Networks, Predictive Maintenance, Prognostics and Health Management | 2023 | 1 | 15 | 183-200 | 10.2478/fas-2023-0012 | Fatigue of Aircraft Structures |
| Anna Polnik1,2 Hubert Matysiak1 Sławomir Czarnewicz3 Zbigniew Pakieła2 | 1) Baker Hughes, al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Faculty of Materials Science and Engineering, Warsaw University of Technology, ul. Wołoska 141, 02-507 Warsaw, Poland 3) Łukasiewicz Research Network, Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | EFFECT OF STRAIN RANGE AND HOLD TIME ON HIGH TEMPERATURE FATIGUE LIFE OF G17CrMoV5-10 CAST ALLOY STEEL | In this work, cast steel G17CrMoV5-10 was investigated. The material subject to investigation as part of this study is commonly used to manufacture steam turbine casings. Modern steam turbines operate under elevated temperature and complex oscillated loads. Thus, the focus of this study was to investigate material under behavior during low cycle fatigue (LCF) test performance at 500°C with and without hold time in tension. During all types of test, cyclic softening of cast steel was noticed. Increasing of total strain rate and applying hold time significantly reduce fatigue life. During hold time, due to temperature and tension the material creep what is confirmed by increasing inelastic stain accommodation. | fatigue, LCF, hold time, strain, steam turbine | 2022 | 1 | 14 | 1-7 | 10.2478/fas-2022-0001 | Fatigue of Aircraft Structures |
| Piotr Reymer1 Andrzej Leski2,3 Marcin Kurdelski3 | 1) Military University of Technology, Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland 2) Łukasiewicz Research Network, Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland 3) Air Force Institute of Technology, Ks. Bolesława 6, 01-494 Warsaw, Poland | SENSITIVITY ANALYSIS OF THE NASGRO EQUATION BASED ON THE PZL-130 TC-II ORLIK TRAINER AIRCRAFT FULL SCALE FATIGUE TEST | The study investigates the sensitivity of numerical crack propagation estimations based on the Nasgro equation. The equation is widely used for crack propagation calculations since it considers the whole range of crack propagation speed from threshold to critical values of stress intensity factor range (ΔK). The presented investigation is based on the actual results of the full scale fatigue test (FSFT) of the PZL-130 ‘Orlik’ TC-II aircraft. We provide a brief description of the test and the general approach followed in crack propagation estimations originally carried out after the test. The obtained results are verified in terms of variation of the input data. Overall results are compared and discussed. | sensitivity analysis, crack propagation, full scale fatigue test | 2022 | 1 | 14 | 8-17 | 10.2478/fas-2022-0002 | Fatigue of Aircraft Structures |
| Mariusz Frankiewicz1 Michał Karoluk1 Robert Dziedzic1 Tristan Timmel2 Peter Scholz3 | 1) Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Lukasiewicza 5, 50-371 Wroclaw, Poland 2) Institute of Lightweight Structures and Polymer Technology, Technische Universität Chemnitz, Reichenhainer Str. 31-33, 09126 Chemnitz, Germany 3) Fraunhofer Institute for Machine Tools and Forming Technology IWU, Reichenhainer Str. 88, 09126 Chemnitz, Germany | THE INFLUENCE OF MATERIAL CONFIGURATION OF FIBRE-METAL LAMINATES WITH ALUMINA CORE ON FLEXURAL STRENGTH | Fibre metal laminates (FMLs) consisting of layers made of PA6 polyamide prepregs reinforced with glass and carbon fibres and an aluminium alloy core are the new variant of the other types used by aerospace FML materials such as GLARE or CARALL. By using a thermoplastic matrix, they can be shaped by stamping processes, which allows for a more efficient production process than classical laminating methods such as vacuum bagging. In addition to the improved impact energy absorption efficiency, the metallic core can be utilised to effectively bond the composite part to adjacent metallic structures. This article presents the influence of the material configuration of fibre-metal laminates consisting of continuous fibre-reinforced thermoplastic outer layers integrated with a layer of metallic aluminium alloy inserts—a number of layers, type and direction of reinforcing fibres—on the static and fatigue flexural properties. In this study, eight laminate configurations were prepared using a one-step variothermal consolidation process. The results showed that in the three-point flexural fatigue test, the samples exceeded 106 cycles at stresses <30% of the static bending strength. Laminates with predominantly longitudinally reinforced layers showed the highest fatigue strength among the FML samples analysed. The type of reinforcing fibres and the number of layers were less affected on the analysed mechanical properties. | fibre-metal laminates, flexural strength, fatigue, composite materials | 2022 | 1 | 14 | 18-28 | 10.2478/fas-2022-0003 | Fatigue of Aircraft Structures |
| Abdelfetah Moussouni 1 Mustapha Benachour 1 Nadjia Benachour 1 | 1) Faculty of Technology and Science, University of Tlemcen, BP 230 – 13000 ChetouaneTlemcen, Algeria | PREDICTION OF FATIGUE CRACKS USING GAMMA FUNCTION | In the present study it has been endeavored to estimate the fatigue crack propagation in V-notch Charpy specimens of 2024 T351 Al-alloy. For this purpose, a new application of fatigue crack growth (FCG) is developed based on the “Gamma function.” Experimental fatigue tests are conducted for stress ratios from 0.1 to 0.5 under constant amplitude loading. The empiric model depends principally on physical parameters and materials’ properties in non-dimensional form. Deviation percentage, prediction ratio, and band error are used for validation of the performance of the fatigue life. The results determined from Gamma application are in good agreement with experimental FCG rates and those obtained from using Paris law. | fatigue crack growth, stress ratio, fatigue, 2024 T351 Al-alloy, Gamma function | 2022 | 1 | 14 | 29-46 | 10.2478/fas-2022-0004 | Fatigue of Aircraft Structures |
| Agata Świerek1 Józef Krysztofik2 Wojciech Matczak3 Antoni Niepokólczycki1,2 | 1) Calisia University, Nowy Świat 4, 62-800 Kalisz, Poland 2) Łukasiewicz Research Network, Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland 3) Aalberts Surface Technologies, ul. Inwestorska 7, 62-800 Kalisz, Poland | CHECKING THE CORRECTNESS OF THE PROCESS OF BRAZING OF THE HONEYCOMB SEAL TO THE BASE BY ULTRASONIC METHOD | This work is focused on the checking of the correctness of the brazing process of honeycomb seals to stationary elements of aircraft turbine engines. It describes this process, paying attention to the aspects that have a fundamental impact on whether the seal will be brazed to the base as required, or whether unacceptable areas of non-brazing will appear. The aim of the study was to check the possibility of using the ultrasonic method to check the correctness of the brazing process of honeycomb seals and to compare the tests carried out using this method with the mostly used visual tests. The research carried out as part of the work showed very well that there are reasons to use the ultrasonic defectoscopy method to test the correctness of the brazing process of honeycomb seals in the elements of aircraft engines. This method also makes it possible to automate the checking process, fully document it and objectively assess the correctness of the connection. The results obtained in the study provide a very good starting point for further research, the aim of which will be to implement the ultrasonic defectoscopy method for testing the correctness of brazing honeycomb seals into practice in industrial conditions. | turbine aircraft engines, honeycomb seals, hard soldering, non-destructive testing, soldering correctness control | 2022 | 1 | 14 | 47-68 | 10.2478/fas-2022-0005 | Fatigue of Aircraft Structures |
| Grzegorz Moneta 1 | 1) Łukasiewicz Research Network, Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | INSIGHT INTO DAMPING SOURCES IN TURBINES | Blade vibrations in aircraft engines are a significant challenge that must be overcome during the design and development of modern turbine engines. Vibrations lead to cyclic displacements and result in alternating stress and strain in undesired environments (high temperatures, erosion, corrosion of the surface, etc.). Under resonance conditions, stress amplitudes can increase and exceed their safety limits, and in extreme cases, can lead to engine failure. One method to reduce resonance vibrations is to increase damping in the turbine assembly. This paper presents and describes vibration damping sources in the turbine, including aerodynamic, material, and friction damping. Additionally, typical damping values for each damping component are presented and compared. | vibrations, blade, gas turbine, turbine engine, damping, FEM, Finite Element Method, transient analysis, explicit, friction damping, under-platform damper, optimization, sensitivity analysis | 2022 | 1 | 14 | 69-82 | 10.2478/fas-2022-0006 | Fatigue of Aircraft Structures |
| Stanisław Gajek 1 | Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | AUTOMATION OF AIRCRAFT FATIGUE LIFE ESTIMATION | The fatigue is an important factor in aircraft operation. A correct estimation of structure fatigue life is crucial for user and payload safety. However, due to high amount of data gathered during a typical recording of load spectra for different types of flights, the overall results become prone to human error. The paper describes development of a software able to perform an automated, in-depth analysis of data recorded with onboard accelerometers. Using the Rainflow Cycle Counting method, it transforms received data points into a Markov matrix. The prepared array is then recalculated into a half-cycle matrix, which can be collapsed into scalar value of fatigue level using the Palmgren-Miner rule. The method was tested with loads recorded during a typical flight conducted according to the Polish NSTS-06 flight scenario and simulated camera mounting fixed to a multirotor. | Aircraft Fatigue, Rainflow Cycle Counting, Load Spectra, UAV | 2022 | 1 | 14 | 83-103 | 10.2478/fas-2022-0007 | Fatigue of Aircraft Structures |
| Zbigniew Skorupka 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | EFFICIENCY AND FATIGUE/ENDURANCE LABORATORY TESTS OF AVIATION FRICTION BRAKES | Brakes are one of the most important safety systems in moving vehicles and machines. In vehicles such as cars or motorcycles brakes are used for stopping, controlling speed, and sometimes changing direction of travel. In aircraft, the main function of brakes is to reduce landing speed. As landing is one of the most dangerous maneuvers in aircraft operation, brakes must be efficient and reliable in order to ensure safety of the crew, passengers, and cargo. The most efficient brakes nowadays are friction brakes where velocity is controlled by friction of a pair of specially designed materials, which ensure stable and high friction coefficient over the course of the required braking process. The process itself is the dissipation of energy during aircraft movement which generates very high temperatures in friction materials during the time of the braking process. The materials and the whole brakes have to be temperature resistant, and we must ensure braking parameters are stable during the whole process. The same principle relates to the endurance/fatigue of the brake assemblies which must be durable enough to survive as high number of braking cycles as possible without any failure, which can result in fatal consequences. Every friction pair and every newly designed brake assembly must be laboratory tested for efficiency and endurance/fatigue in order to be used in an aircraft or vehicle. In this paper, we present the basic set of laboratory tests in the scope of friction materials and brake assemblies. Results of the tests are used as confirmations/proofs of proper and safe operation of the brakes for use in vehicles, especially in aircraft but also in land-based vehicles. | fatigue, endurance, brakes, friction material, landing gears, laboratory tests, dynamic testing | 2022 | 1 | 14 | 104-113 | 10.2478/fas-2022-0008 | Fatigue of Aircraft Structures |
| Rodzewicz Mirosław1 Głowacki Dominik1 Hajduk Jaroslaw2 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw,Poland 2) Air Force Institute of Technology, Księcia Bolesława 6, 01-494 Warsaw, Poland | COMPARATIVE ANALYSIS OF THE LOAD SPECTRA RECORDED DURING PHOTOGRAMMETRIC MISSIONS OF LIGHTWEIGHT UAVS IN TAILLESS AND CONVENTIONAL CONFIGURATIONS | The purpose of this article is to present the results of the investigation regarding the differences of the load spectra of two unmanned fixed-wing aircraft performing photogrammetry missions: X-8 (flying wing) and PW-ZOOM (conventional configuration). The focus was on the analysis of a number of load cycles for various load increments within the range of the operational loads. The load spectra were determined using the acceleration signal recorded in the autopilot logs as an input. This signal was transferred to the chain of local extreme values scaled in the form of discrete load levels, and then the transfer arrays were derived with use of the rainflow counting algorithm. On this basis, the incremental load spectra were determined for each flight. These load spectra were subjected to statistical analyses to determine the load spectra representative of the flight sessions in a few ways between non-conservative (i.e., focused on average load histories) and conservative (i.e., focused on the worst load histories observed during the flight session). Finally, the fatigue life was calculated by having the structural element of the assumed fatigue properties subjected to the load spectra of both airplanes. A large (exceeding one order of magnitude) difference in the number of load cycles for larger load increments in the analyzed load spectra was shown. This difference is related to the different dynamic characteristics of the two aircraft, in particular the gust response. As a result, there is a several-fold difference in fatigue life. | load spectra, fatigue life, unmanned aircraft, photogrammetry mission | 2022 | 1 | 14 | 114-134 | 10.2478/fas-2022-0009 | Fatigue of Aircraft Structures |
| Michał Sałaciński1 Kamil Dydek2 Andrzej Leski4 Rafał Kozera2 Mateusz Mucha3 Wojciech Karczmarz1 | 1) Air Force Institute of Technology 01-494 Warsaw, Ksiecia Boleslawa 6, Poland 2) Warsaw University of Technology, Faculty of Materials Science and Engineering 02-507 Warsaw, Woloska 141, Poland 3) Polish Air Force University 08-521 Deblin, Dywizjonu 303 35, Poland 4) Łukasiewicz Research Network – Institute of Aviation 02-256 Warsaw, Aleja Krakowska 110/114, Poland | IMPACT OF CARBON NANOTUBES ON THE MECHANICAL AND ELECTRICAL PROPERTIES OF SILICONE | This paper presents the results of a structure study of a dispersion composite on a silicone matrix with a filler in the form of multi-walled carbon nanotubes (MWCNTs). The study aims to determine the effect of the filler on the composite mechanical properties and electrical conductivity. Materials that are electrically conductive and exhibit high mechanical properties can find applications in high-strain sensors. During the study, the characteristic properties of the susceptible materials, silicone alone and silicone with different filler contents (4%, 6%, and 8% by weight), were determined after curing. Microscopic observations were performed to assess the influence of carbon fillers on the material structure and to determine the level of homogeneity of the material. Examination of mechanical properties facilitated the determination of the Shor A hardness (ShA), stiffness, and Poisson’s ratio of the cured composites, depending on the nanotubes’ content. In parallel with the study of mechanical properties, the effect of loading, and the associated deformation of the samples, on the conductivity of the composite was investigated. Based on the results obtained, a discussion was carried out on the type of conductivity characteristic of silicone with different filler content as well as depending on the level of deformation of the samples. | nanotubes; silicon, mechanical properties, electrical properties | 2022 | 1 | 14 | 135-153 | 10.2478/fas-2022-0010 | Fatigue of Aircraft Structures |
| Rafał Luziński 1 Piotr Synaszko 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Bolesława Street, 6, 01-494 Warsaw, Poland | APPLICATION OF DIGITAL RADIOGRAPHY (DR) IN AN APPROACH TO EVALUATE THE TECHNICAL CONDITION OF MIG-29’S VERTICAL STABILIZERS | The purpose of the work presented was to evaluate the capabilities of digital radiography to detect cracks in the internal structure of MiG-29 vertical stabilizers. The test object was a stabilizer previously subjected to fatigue testing and partially torn down for the needs of visual inspection. An inspection of three regions containing cracked parts was performed, with use of a pulsed x-ray generator and digital detector array. The results confirmed the method could be used to detect cracks in an internal structure which could not be inspected with other methods without affecting the stabilizer’s integrity. | NDT, digital radiography, inspection of internal structures, composite structures | 2021 | 1 | 13 | 1-7 | 10.2478/fas-2021-0001 | Fatigue of Aircraft Structures |
| Zbigniew Skorupka 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | LIFT FORCE MEASUREMENT IN LANDING GEARS DYNAMIC TESTS | As one of the key components of the aircraft in terms of both operation and safety landing gears are of special interest of the aviation regulations. During the touch down landing gears need to dissipate as much of the energy as possible maintaining the lowest volume and weight as required by the aviation design restrictions. According to the aviation regulations landing gears have to be tested in order to prove the dissipation of the calculated landing energy and to evaluate actual loads acting on the fuselage via the mounting nodes of the landing gears. The tests need to replicate the real landing conditions as closely as possible – including the lift force (or lift) acting on the aircraft during landing. The lift force during landing is not sufficient to maintain the aircraft in flight but acts as the relief force to the aircraft weight resulting in lowering loads applied to the fuselage and decreasing landing energy needed to be dissipated. The lift force or lift has to be taken into account during laboratory tests of landing gears. The lift force needs to be simulated in all of the landing gears dynamic tests: performance optimization, proof of the operation for the certification, and the fatigue evaluation. There are two main methods of applying the lift during the tests: equivalent/effective mass or direct lift application. The latter is used at the Landing Gear Laboratory of the Lukasiewicz Research Network – Institute of Aviation (where author works on daily basis). The lift is applied by the pneumatic cylinders built in the test stand. Until recently the control of the lift force value was performed indirectly by the measurement of the pressure inside the pneumatic system. Recently the experimental direct measurement system using force transducers was introduced in order to directly measure the lift force during every test. In the presented paper, the author gives an overview of the lift force measurement system including its design and the results of the preliminary use evaluation. | fatigue, Landing Gears, laboratory tests, dynamic testing, lift force measurement | 2021 | 1 | 13 | 8-16 | 10.2478/fas-2021-0002 | Fatigue of Aircraft Structures |
| Marek S. Łukasiewicz 1 | 1) Warsaw University of Technology, Faculty of Power and Aeronautical Engineering, Nowowiejska 24, 00-665 Warsaw, Poland | LOAD SPECTRUM ANALYSIS WITH OPEN SOURCE SOFTWARE – AN APPLICATION EXAMPLE | Processing of digital experimental data has become a key part of virtually every research project. As sensors get both more diverse and cheaper, the amount of information to be handled greatly increases as well. Especially fatigue failure modelling requires by its nature large numbers of samples to be processed, and visualised. The presented paper is based on analysis of load data gathered in flight on an unmanned aircraft. A few versions of an analysis program were developed and considered for the use case. Each implementation included ingesting the data files, creating transfer arrays and the “rain flow counting” algorithm. For the sake of the ease of use and functionality, the version based on Python programming language was selected for presentation. Short development iteration time of this approach allowed gaining new insights by tweaking parameters to better represent actual acquired data. Both the results and the software itself can be easily viewed in a web browser and run with modifications without the need to install any software locally. The developed software is meant as a demonstration of capabilities of open source computation tools dedicated to aerospace and mechanical engineering research, where they remain relatively unpopular. | load spectrum, rainflow counting, data visualisation | 2021 | 1 | 13 | 17-30 | 10.2478/fas-2021-0003 | Fatigue of Aircraft Structures |
| Józef Krysztofik 1 Maciej Malicki 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | DETECTION OF SUB-SURFACE DEFECTS IN SEMI-FINISHED PRODUCTS FROM ALUMINUM ALLOYS BY THE EDDY CURRENT METHOD | The article presents the results of tests aimed at detecting discontinuities in the subsurface layer of elements intended for further processing. For the initial identification of discontinuities, the method of computed tomography was used. Based on the tomographic images of selected typical defects and measurements of the electrical conductivity of the material, the parameters for the eddy current tests were determined. A series of discontinuities in the subsurface layer to a depth of about 0.48 mm were detected. This allowed, at a given stage of machining, relevant elements to be selected for further processing. | eddy current testing, tomographic testing, subsurface discontinuities, standard depth of penetration, effective depth of penetration | 2021 | 1 | 13 | 31-39 | 10.2478/fas-2021-0004 | Fatigue of Aircraft Structures |
| Grzegorz Moneta 1 Jerzy Jachimowicz 2 Marek Pietrzakowski 3 Adam Doligalski 1 Jarosław Szwedowicz 4 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland 3) Warsaw University of Technology, plac Politechniki 1, 00-661 Warsaw, Poland 4) Zurich University of Applied Sciences, Technikumstrasse 9, 8400 Winterthur, Switzerland | INSIGHT INTO VIBRATION SOURCES IN TURBINES | Despite of nearly 100 years of turbine engine development and design, blade vibrations remain a great engineering challenge. The rotating turbine blades’ vibrations lead to cyclic oscillations, which result in alternating stress and strain in harsh environments of high temperature and pressure. In modern aeroengines, high hot flow velocities might generate erosion and corrosion pitting on the metal surfaces, that leverage remarkably mean stresses. The combination of both mean and alternating stresses can lead to unexpected engine failures, especially under resonance conditions. Then, alternating stress amplitudes can exceed the safety endurance limit, what accelerates the high cyclic fatigue leading quickly to catastrophic failure of the blade. Concerning the existing state-of-the-art and new market demands, this paper revises forced vibrations with respect to excitation mechanisms related to three design levels: (i) a component like the blade design, (ii) turbine stage design consisting of vanes and blades and (iii) a system design of a combustor and turbine. This work reviews the best practices for preventing the crotating turbine and compressor blades from High Cyclic Fatigue in the design process. Finally, an engine commissioning is briefly weighed up all the pros and cons to the experimental validations and needed measuring equipment. | vibrations, blade, gas turbine, turbine engine, strain gauge, tip timing, Additive Manufacturing | 2021 | 1 | 13 | 40-53 | 10.2478/fas-2021-0005 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Andrzej Kubit 2 Tomasz Trzepieciński 2 Grzegorz Moneta 1 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Rzeszów University of Technology, Al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland | EXPERIMENTAL AND NUMERICAL STRESS STATE ASSESMENT IN REFILL FRICTION STIR SPOT WELDING JOINTS | Refill Friction Stir Spot Welding (RFSSW) is a technology used for joining solid materials that was developed in Germany in 2002 by GKSS-GmbH as a variant of the conventional friction stir spot welding (FSSW) [1]. In the RFSSW technology, the welding tool consists of a fixed outer part and rotating inner parts, which are called a pin and a sleeve. The tool for RFSSW is designed to plasticize the material of the parts to be joined by means of a rotary movement. The design of the tool allows independent vertical movement of both elements of the welding tool. This allows obtaining spot welds without creating holes that could weaken the structure. The main advantage of RFSSW is the potential for replacing the technologies that add weight to the structure or create discontinuities, such as joining with screws or rivets. Thus, RFSSW has great potential in the automotive, shipbuilding and aviation industries. Furthermore, the technology can be used to join different materials that could not be connected using other joining methods. The main objective of this work is to understand the physical and mechanical aspects of the RFSSW method – including the residual stress state inside the weld and around the joint. The results of the investigations can help to determine optimal parameters that could increase the strength and fatigue performance of the joint and to prove the significant advantage of RFSSW connections over other types of joints. The work assumes the correlation of two mutually complementary investigation methods: numerical analyses and experimental studies carried out with diffraction methods. The comparison between numerical and experimental results makes potentially possible the determination of degree of fatigue degradation of the material by observing the macroscopic stress state and the broadening of the diffraction peak width (FWHM), which is an indicator of the existence of micro-stress related to the dislocation density and grain size. | RFSSW, X-ray diffraction, finite elements modelling, stress state, aluminium alloys | 2021 | 1 | 13 | 54-71 | 10.2478/fas-2021-0006 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Łukasz Pawliszak 1 Grzegorz Moneta 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | APPLICATION OF LABORATORY DIFFRACTION METHODS IN CHARACTERIZATION OF ELEMENTS MADE BY ADDITIVE SLM METHODS – STATE OF THE ART | The greatest challenge of widely developed incremental manufacturing methods today is to obtain, as a result of the manufacturing process, such components that will have acceptable strength properties from the point of view of a given application. These properties are indirectly determined by three key characteristics: the level of surface residual stress, the roughness of the component and its porosity. Currently, the efforts of many research groups are focused on the problem of optimizing the parameters of incremental manufacturing so as to achieve the appropriate level of compressive residual stress, the lowest possible porosity and the lowest possible roughness of parts obtained by 3D methods. It is now recognized that determining the level of these three parameters is potentially possible using experimental X-ray diffraction methods. The use of this type of radiation, admittedly, is only used to characterize the surface layer of elements, but its undoubted advantage is its easy availability and relatively low cost compared to experiments carried out using synchrotron or neutron radiation. | X-ray diffraction, residual stress measurements, additive manufacturing, SLM | 2021 | 1 | 13 | 72-80 | 10.2478/fas-2021-0007 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Łukasz Pawliszak 1 Grzegorz Moneta 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | LASER POWDER BED FUSION AND SELECTIVE LASER MELTED COMPONENTS INVESTIGATED WITH HIGHLY PENETRATING RADIATION | Methods of incremental manufacturing, i.e. 3D printing, have been experiencing significant growth in recent years, both in terms of the development of modern technologies dedicated to various applications, and in terms of optimizing the parameters of the process itself so as to ensure the desired mechanical and strength properties of the parts produced in this way. High hopes are currently being pinned on the use of highly penetrating types of radiation, i.e. synchrotron and/or neutron radiation, for quantitative identification of parameters characterizing objects produced by means of 3D printing. Thanks to diffraction methodologies, it is feasible to obtain input information to optimize 3D printing procedures not only for finished prints but also to monitor in situ printing processes. Thanks to these methodologies, it is possible to obtain information on parameters that are critical from the perspective of application of such obtained elements as stresses generated during the printing procedure itself as well as residual stresses after printing. This parameter, from the point of view of tensile strength, compression strength as well as fatigue strength, is crucial and determines the possibility of introducing elements produced by incremental methods into widespread industrial use. | neutron diffraction, synchrotron diffraction, residual stress measurements, additive manufacturing, SLM, LPBF | 2021 | 1 | 13 | 81-98 | 10.2478/fas-2021-0008 | Fatigue of Aircraft Structures |
| Marzena Wichniarz 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | CERTIFICATION OF TESTING LABORATORIES –THE BASIS OF RELIABILITY AMONG RESEARCH VENDORS IN AVIATION | Material characterization and assessment is a crucial stage in most of aviation and aeronautical research and a basis for further design and testing of more complex aircraft elements and structures. Material test’s reliability can only be guaranteed by conducting them at independent and reliable laboratories, operating based on a management system assessed by a third-party such as the accreditation according to the ISO/ IEC 17025 or NADCAP or having the qualification of the second-party based on specific customer requirements. This paper introduces basic requirements for material testing laboratories according to accreditation systems and describes its responsibilities as qualified and reliable testing suppliers. | certification, accreditation, NADCAP, ISO/ IEC 17025, standardization, material test, standard, management system, quality, laboratory, validation, reliability | 2021 | 1 | 13 | 99-105 | 10.2478/fas-2021-0009 | Fatigue of Aircraft Structures |
| Krzysztof Stanisław Szafran 1 Marcin Michalczyk 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | RESEARCH ON HOVERCRAFT – FATIGUE CRACKS IN THE ENGINE FRAME | Rescue patrol hovercrafts must meet the basic condition – high reliability of use in extreme conditions. The introduction to the work shows damage to the propulsion system and the fan tunnel structure resulting from a fatigue fracture of the attachment wound to the propulsion unit hull. In this paper, the author describes some ways of improving the engine frame structure. In the first phase of the exploitation crack testing of the hovercraft frame, the probable causes of damage were determined. The necessary output data for analysis of the load course were obtained from the operating documentation. The approximate number of variable load cycles acting on the frame truss rod was determined. Using the comparative testing methods, the service life of the frame was estimated. Probable resonance frequencies of the vibrating bars in the truss were determined. Vibration tests of the power transmission assemblies were carried out, which allowed to determine the amplitudes and frequencies of free vibrations. Finally, a modification of the frame shifting the resonant frequency range was proposed. In conclusions, changes to the design and a schedule of inspections were proposed. The newly designed engine frame should have an extended service life. | rescue, hovercraft exploitation, fatigue degradation, mission safety | 2021 | 1 | 13 | 106-115 | 10.2478/fas-2021-0010 | Fatigue of Aircraft Structures |
| Tayeb Kebir 1 José A.F.O. Correia 2 Mohamed Benguediab 3 Abdellatif Imad 4 | 1) Department of Technical Sciences, Institute of Science and Technology, University Center Salhi Ahmed, Naama, Algeria 2) Researcher & Invited Professor, CONSTRUCT & Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal 3) Laboratory of Materials and Systems Reactive, Faculty of Technology, Universty of Sidi Bel Abbes, Algeria 4) Laboratory of Mechanical of Lille, University of Lille1, Polythech’Llle1, France | A FCG MODEL AND THE GRAPHICAL USER INTERFACE UNDER MATLAB FOR PREDICTING FATIGUE LIFE: PARAMETRIC STUDIES | The focus of this research work was predicting the fatigue life of mechanical components used for industrial and transport systems. To understand how the phenomenon of fatigue occurs in a material, the fatigue crack growth is studied. The purpose of this work was to create a graphical user interface (GUI) under Matlab to allow researchers to conduct the parametric studies of fatigue crack propagation to predict fatigue life. In this work, three models for fatigue crack propagation were used: those of Paris, Walker and Forman in order to study the three parameters: the Paris exponent m, load ratio R and hardness KIC, respectively. In addition, a novel model FCG was developed to study the influence of the hardening parameters (K′, n′) on fatigue crack propagation. The comparison of the simulation results with those in the literature shows good agreement. | Fatigue life prediction; Graphical User Interface, fatigue crack growth; cyclic hardening; Paris; Walker; Forman | 2021 | 1 | 13 | 116-139 | 10.2478/fas-2021-0011 | Fatigue of Aircraft Structures |
| Ayiei Ayiei1 Luke Pollock1 Fatima Najeeb Khan2 John Murray3 Glenn Baxter4 Graham Wild5 | 1) School of Engineering, RMIT University, Melbourne 3000, Australia 2) The University of Management and Technology, Johar Town, Lahore, Punjab 54770, Pakistan 3) School of Engineering, Edith Cowan University, Joondalup 6027, Australia 4) School of Tourism and Hospitality Management, Suan Dusit University, Thailand 5) School of Engineering and Information Technology, UNSW, Canberra 2612, Australia | THE ROLE OF LEADERSHIP IN AVIATION SAFETY AND AIRCRAFT AIRWORTHINESS | Ensuring aircraft are technically safe to operate is the realm of airworthiness, literally worthy of being in the air. This is achieved not only with technological tools and techniques, or with just personnel and manpower, it is guided and supervised by managers and leaders. As such, the objective of this paper is to understand the role leadership plays in maintaining aviation safety and aircraft airworthiness. To this end, a case study of the Hawker Sidley Nimrod XV230 accident that occurred on September 2, 2006 near Kandahar in Afghanistan, was utilized. The study concluded that leadership is a key aspect, specifically finding that leaders are responsible for articulating the organizations vision, strategic objective setting, and monitoring the achievement of those objectives. It was concluded that operational airworthiness is directly dependent on the leadership ability to provide direction, workplace culture, continued learning, and establish risk management systems for safe and airworthy operations. | aviation safety, airworthiness, aircraft accidents, leadership | 2020 | 1 | 12 | 1-14 | 10.2478/fas-2020-0001 | Fatigue of Aircraft Structures |
| Bartosz Madejski1 Maciej Malicki1 Sławomir Czarnewicz1 Konrad Gruber2 | 1) Łukasiewcz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Wrocław University of Science and Technology, Faculty of Mechanical Engineering, Łukasiewicza Street 5, 50-371 Wrocław, Poland | MICROSTRUCTURAL AND MECHANICAL PROPERTIES OF SELECTIVE LASER MELTED INCONEL 718 FOR DIFFERENT SPECIMEN SIZES | Selective laser melting (SLM) falls into the category of additive manufacturing technologies that are being increasingly used in the aerospace industry. This study presents the results of the examination of the microstructure and mechanical properties of selective laser melted Inconel 718. The tests were carried out for samples of different geometry (thickness, shape). The investigation showed the effect of the specimen’s size and the printing direction on the microstructure and mechanical properties. In the microstructural investigation, light and scanning electron microscopes were used. The microstructure investigation included measurements of the grain size and the carbides’ content. In order to estimate porosity computer tomography was used. Tensile tests were carried out at room temperature. The results showed differences in mechanical and microstructural properties of different size specimens. | additive manufacturing, tensile test, microstructure investigation, IN718, Inconel 718 | 2020 | 1 | 12 | 15-26 | 10.2478/fas-2020-0002 | Fatigue of Aircraft Structures |
| Akshansh Mishra 1,2 | 1) Department of Mechanical Engineering, Politecnico Di Milano, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy 2) Centre for Artificial Intelligent Manufacturing Systems, Neural Net, India | DISCRETE WAVELET TRANSFORMATION APPROACH FOR SURFACE DEFECTS DETECTION IN FRICTION STIR WELDED JOINTS | Friction Stir Welding joint quality depends on input parameters such as tool rotational speed, tool traverse speed, tool tilt angle and an axial force. Surface defects formation occurs when these input parameters are not selected properly. The main objective of the recent paper is to develop Discrete Wavelet Transform algorithm by using Python programming and further subject it to the Friction Stir Welded samples for the identification of various external surface defects present. | Machine Vision; Surface Defects; Friction Stir Welding; Python programming | 2020 | 1 | 12 | 27-35 | 10.2478/fas-2020-0003 | Fatigue of Aircraft Structures |
| Tamer Saraçyakupoğlu 1 | 1) Istanbul Gelisim University, Department of Aeronautical Engineering, 34315, Istanbul, Turkey | THE FRACTOGRAPHIC INVESTIGATION OF AN AEROENGINE ACCESSORY GEARBOX QUILL SHAFT | This paper analyzes the fracture of the quill shaft. An investigation of a twin-engine trainer aircraft incident has been reported. The incident occurred due to the right electric generator out and low oil pressure. The main failure based on the warnings and the subsequent incident was identified. The failure involved the fatigue fracture of the quill shaft on the J85 turbojet engine's accessory drive gearbox (ADG) and Input Drive Assembly (IDA). It was determined that the fracture had been originated by the torsional loads impacting the quill shaft that connects the ADG and IDA. The quill shaft was broken as the loads excessed the limit values designed by the manufacturer as a system protection part. Although the main failure was successfully identified, further analysis regarding the reaching to the triggering cause of the fracture was performed. Through the detailed fractographic and metallographic studies, the rootcause of the fracture was determined as the misalignment of the quill shaft between ADG as the driving unit and IDA as the driver unit. | J-85, Accessory Drive Gearbox, Crack, Fracture, Torsional Overload | 2020 | 1 | 12 | 36-46 | 10.2478/fas-2020-0004 | Fatigue of Aircraft Structures |
| Amaury Chabod 1 Nicolas Baron 1 | 1) HBK France PRENSCIA, 3 chemin de la Dîme, 95700 Roissy-en-France | DIGITAL TWIN FOR FATIGUE ANALYSIS | The main design parameters that impact the fatigue of components are geometry, material and loading. Simulation with Finite Element Analysis (FEA) and tests on a vibrating table are often used to understand the dynamic behaviour of components and thus validate those items. Accelerated tests are used for the mission profile and test definition, as described in GAM-EG-13, MIL-STD-810F and RTCA DO-160E. The shock response spectrum (SRS) and the extreme response spectrum (ERS) allow for a comparison of the power spectrum density (PSD) and the acceleration factor applied in terms of fatigue severity through the fatigue damage spectrum (FDS). In addition, the hypothesis of linear damage accumulation enables the combination of several events for specifying a mission profile. Ultimately, the mission profile, which represents a usage that might span over several years, can be reduced to a shorter duration with a damage extraction technique. This is particularly useful for the definition of vibrating table specifications. An advantage of the virtual vibrating table is the reduction of the number of prototypes and the understanding of failure modes. To achieve this objective, finite element analysis in the frequency domain (harmonic analysis) is used and the structural stress response is evaluated with a PSD loading. A statistical model of rainflow allows assessing the damage on the components. The presentation also shows the effects of the damping factor on damage results. To achieve accurate results and define a Digital Twin, the correlation between test results and the finite element analysis is fundamental. Experimental modal analysis, based on the measured acceleration responses, helps to validate calculated modal frequencies and to assess the damping for each mode. This study shows the importance and the sensitivity on damping of the structural response, and in turn on fatigue. | Fatigue analysis, digital twin method, modal analysis, test-FEA correlation | 2020 | 1 | 12 | 47-56 | 10.2478/fas-2020-0005 | Fatigue of Aircraft Structures |
| Paulina Kamińska 1 Piotr Synaszko 1 Patryk Ciężak 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland | ANALYSIS OF THE CORROSION RESISTANCE OF AIRCRAFT STRUCTURE JOINTS WITH DOUBLE-SIDED RIVETS AND SINGLE-SIDED RIVETS | An important factor having a negative impact on the technical condition of aircraft structure elements is the adverse effect of the atmosphere, which causes formation of corrosion in aircraft structures, especially in riveted lap joints. The electric potential difference between the sheet material and the rivet, in the presence of humid air, may cause electrochemical corrosion. The paper presents specimens that imitate the repair on the Mi-24 helicopter with the use of blind rivets in places where solid double-sided rivets could not be used. The aim of the research was to assess the corrosion resistance of lap joints with the use of single-sided and double-sided rivets. The analysis of corrosion resistance was carried out based on accelerated aging tests in a salt spray chamber. The salt chamber tests were aimed at determining the changes taking place in the specimens exposed to the marine environment. In the course of periodic observations changes in the mass of the specimens and in the form of corrosion losses were recorded. These activities were aimed at determining whether the exposure of specimens in the salt chamber causes electrochemical corrosion or pillowing. In addition, the specimens were subjected to static strength tests to assess the effect of corrosion on the strength properties of riveted joints. | rivet joints, double-sided rivets and one-sided rivets, corrosion, accelerated ageing tests | 2020 | 1 | 12 | 57-68 | 10.2478/fas-2020-0006 | Fatigue of Aircraft Structures |
| Zbigniew Skorupka 1 | 1) Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114 Warsaw, Poland | DYNAMIC FATIGUE TESTS OF LANDING GEARS | Landing gears are one of the main components of an aircraft. The landing gear is used not only during take-off and landing but also, in most cases, during ground manoeuvres. Due to its function, the landing gear is also one of the key safety components of the aircraft due to dissipating landing loads acting on the aircraft. The mentioned loads come from both the vertical and horizontal speeds during touchdown and by the aircraft’s losing the speed by braking. The landing gear is then loaded with constantly changing forces acting in various directions during every landing, with the only difference coming from their magnitude. The repeatable loading conditions cause significant wear of the landing gear. This wear can be divided into two categories, one is the wear of consumable parts such as the brake linings and the other is the fatigue wear of the structural components. The latter type of wear is much more dangerous due to its slow, and in many cases, unnoticeable progression. Fatigue wear can be estimated by numerical analyses – this method works with a great degree of probability on single components but due to the complexity of the landing gear as a whole it is not precise enough to be applied to the full structure. In order to evaluate the fatigue of the whole landing gear the best method accepted by regulations is the laboratory testing method. It involves a series of various drop tests resembling the real landing condition distribution. The aim of the tests is to check the fatigue wear of the landing gear and to prove its reliability for certification and/or operational purposes. In this paper the author describes the basics of the landing gear fatigue wear, possibilities of its evaluation and presents laboratory dynamic method used for extensive tests in life-like operation conditions. | fatigue, landing gears, laboratory tests, dynamic testing | 2020 | 1 | 12 | 69-77 | 10.2478/fas-2020-0007 | Fatigue of Aircraft Structures |
| Andrzej Leski1 Wojciech Wronicz2 Piotr Kowalczyk2 Michał Szmidt2 Robert Klewicki2 Karol Włodarczyk2 Grzegorz Uliński2 | 1) Military University of Technology, Sylwestra Kaliskiego Str. 2, 00-908 Warsaw, Poland 2) Łukasiewicz Research Network ‒ Institute of Aviation, Krakowska Av. 110/114, 02-256, Warsaw, Poland | MODULAR TEST STAND FOR FATIGUE TESTING OF AERONAUTICAL STRUCTURES – VERIFICATION OF ASSUMPTIONS | The Modular Test Stand was developed and manufactured to decrease the cost of fatigue testing and reduce the time of its completion as well as to enable testing specimens under more complex load conditions. The stand consists of three connected sections, similar to a wing box, all being loaded in the same way. Thanks to that, several specimens can be tested simultaneously. This configuration requires that stress and strain distribution should be reasonably uniform, as assumed in the design stage. The structure can be loaded with bending or torsion. A whole section, selected structural node or a specimen mounted in the structure as well as a repair or a sensor can be a test object. Two stands, one for bending and one for torsion were prepared. This paper presents the verification of the assumed strain and stress distributions on the skin panels. The measurements were performed with the use of Digital Image Correlation (DIC) as well as strain gauges. DIC measurements were performed on one skin panel of the central section. Five strain gauge rosettes were installed on both panels of the one section. In addition, one rosette was applied to one skin panel in each of two other sections. Measurements were performed on the stand for torsion as well as on the stand for bending. The results of DIC analysis and strain gauge measurement during torsion show uniform shearing strain distributions on the panels. During bending, on the tensioned side, the strains obtained indicate quite uniform strain distributions. On the compressed side, local buckling of the skin panels results in high strain gradients. Strain levels obtained with the use of a DIC analysis and strain gauge measurements were similar. Moreover, horizontal displacements of markers in the spar axis during DOI: 10.2478/fas-2020-0008 FATIGUE OF AIRCRAFT STRUCTURES Volume 2020: Issue 12, pp. 78-91 bending was determined based on a series of photographic. The deflection line obtained in this way has a shape similar to arc, which is characteristic of the constant bending moment. The stand was tested with torsional and bending loads in order to verify the design assumptions. The results of strain distributions on the skin panels with the use of DIC and strain gauges as well as the deflection line of the spar axis indicate that the Modular Test Stand performs as assumed and can be used for tests. | Fatigue, Test, Airframe, Veryfication, Strain Gauge, DIC | 2020 | 1 | 12 | 78-91 | 10.2478/fas-2020-0008 | Fatigue of Aircraft Structures |
| Jerzy Jachimowicz 1 Grzegorz Moneta 2 | 1) Military University of Technology, Sylwestra Kaliskiego Str. 2, 00-908 Warsaw, Poland 2) Łukasiewicz Research Network ‒ Institute of Aviation, Krakowska Av. 110/114, 02-256, Warsaw, Poland | IMPACT OF MANUFACTURING TOLERANCES ON STRESS IN A TURBINE BLADE FIR-TREE ROOT | Low Cycle Fatigue (LCF) is one of most common mechanisms behind turbine blade failures. The reason is high stress concentration in notch areas, like fir-tree root groves, which can cause cyclic stress beyond the safe threshold. The stress levels strictly depend on the manufacturing accuracy of the fir-tree lock (for both fitted together: blade root and disk groove). The probabilistic study aimed at determination of stress was performed using Finite Element Method (FEM) simulation on a population of 1000 turbine models (disk + blades +friction dampers), where fir-tree lock dimensions were sampled according to the normal distribution, within limits specified in the documentation. The studies were performed for different manufacturing quality levels: 3-Sigma, 6-Sigma and 3-Sigma with tolerance ranges reduced twice. Based on the results, the probabilistic distributions, probabilities and expected ranges of values could be determined for: material plastification, stress, strain, LCF lifetime, etc. The study has shown how each tooth of the root is loaded and how wide a stress range should be expected in each groove. That gives information on how the definition of tolerances should be modified to make the construction more optimal, more robust, with lower likelihood of damage, taking into account the cost-quality balance. It also shows how the Six Sigma philosophy can improve the safety of the construction, its repeatability and predictability. Additionally, the presented numerical study is a few orders of magnitude more cost- and time-effective than experiment. | fir-tree root, turbine, lock, blade, disk, manufacturing tolerances, Monte-Carlo simulations, Six Sigma, Low Cycle Fatigue, Design of Experiment | 2020 | 1 | 12 | 92-101 | 10.2478/fas-2020-0009 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 | 1) Department of Components Manufacturing and Production Organization, Faculty of Mechanics and Technology, Rzeszow University of Technology, Kwiatkowskiego 4, 37-450 Stalowa Wola, Poland | SOME COMMENTS ON FATIGUE LIFE TESTS OF AIRCRAFT CABLE CONTROL SYSTEMS | Cable control systems are widely used in aircraft and gliders. This paper deals with the problem of collecting real loads acting cable control systems and cable tests preparation (load spectrum) and performance. The author proposes a method for defining real loads acting on control systems, preparing and carrying out fatigue tests of cables revealing symptoms of fretting. The fatigue tests results can be used to predict service life, to plan and prepare periodic and details inspections. This method could be used to increase service life of aircraft control cables and could help to replace the commonly used Time-Based Maintenance (TBM) strategy with the Damage Tolerance (DT). | aircraft’s cable control systems, cable service life, cable fatigue tests | 2020 | 1 | 12 | 102-112 | 10.2478/fas-2020-0010 | Fatigue of Aircraft Structures |
| Krzysztof Stanisław Szafran 1 Ireneusz Kramarski 2 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) HORNET, ul. Dębowa 72/33, 05-100 Nowy Dwor Mazowiecki, Poland | SERVICE LIFE EXTENSION OF PARACHUTES WITH USE OF NON-DESCTRUCTIVE AND PARTIALLY DESTRUCTIVE TESTING METHODS OF TEXTILE MATERIALS | The specificity of personal rescue and reserve parachutes is the fact that they are practically never used for jumping during their service life as they are intended for use only in emergency situations. Therefore, these parachutes throughout the entire period of use are only periodically aired and repacked every 6-12 months. Airing and repacking is necessary even if the parachute is only stored. Rescue and reserve parachutes’ components wear unevenly because the canopy with the suspension lines is inside the container and the cover, while the external components of the harness and the container undergo typical operational wear. Therefore, the service life of rescue parachutes can even reach 20 years (this refers to the canopy with the suspension lines alone). During normal exploitation, parachutes are subjected to non-destructive visual and tactile inspection in preparation for packing. When a parachute reaches its maximum service life, extension of its service life can be calculated based on its technical condition. The procedure for extending parachute’s service life involves non-destructive tests at a fabric air permeability test stand and partially destructive tests at the strength test stand. In the paper, both methods are described and their advantages and disadvantages are discussed. Also, observations some regarding the packers’ work and the desired new properties of raw materials that could be introduced to the parachute industry are presented. | parachute systems, textile materials, fatigue degradation, service life, aviation safety | 2020 | 1 | 12 | 113-122 | 10.2478/fas-2020-0011 | Fatigue of Aircraft Structures |
| Marta Baran1 Dominik Nowakowski1 Janusz Lisiecki1 Sylwester Kłysz1,2 | 1) Air Force Institute of Technology, Księcia Bolesława 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury in Olsztyn, Department of Technical Sciences, Michała Oczapowskiego 2, 10-719 Olsztyn, Poland | MECHANICAL TESTS APPLIED TO STRUCTURAL HEALTH MONITORING: AN OVERVIEW OF PREVIOUS EXPERIENCE | Laboratory for Materials Strength Testing (LMST) has been conducting accredited mechanical research for aviation from 2003. Among accredited procedures are e.g. low and high cycle fatigue tests, fracture toughness tests and fatigue crack growth rate tests. The main goal of them is obtaining materials constants and characteristics. However knowledge how to conduct these tests could be used also in other applications, for instance in the work on development of Structural Health Monitoring systems (SHM). When cracks propagate in a controlled way in laboratory conditions, it allows verifying the operation of a single sensor or a network of sensors. In this paper, an overview of mechanical tests carried out at the Laboratory for Materials Strength Testing within Air Force Institute of Technology (AFIT) work on research and development of SHM systems is presented. Specimens prepared from materials such as aluminum alloys (among other withdrawn PZL-130 Orlik TC-II aircraft) and CFRP composite were tested under different mechanical loads, i.e., cycle and impact loads. In the presented research, both constant amplitude and spectrum loads were applied. | BVID, CFRP, composite damage, fatigue crack, SHM | 2020 | 1 | 12 | 123-135 | 10.2478/fas-2020-0012 | Fatigue of Aircraft Structures |
| Shawn You1 X. Shawn Gao2 Arlin Nelson3 | 1) MTS Systems Corporation, 14000 Technology Drive, Eden Prairie, MN 55344, USA | BREAKING THE TESTING PYRAMID WITH VIRTUAL TESTING AND HYBRID SIMULATION | Virtual testing and hybrid simulation have become an important trend in airplane design and validation. The traditional Testing Pyramid (or Building Block) approaches that emphasis on uniaxial coupon test and full structure certification test are being challenged. Researchers are trying to use advanced testing and simulation methods to replace the Testing Pyramid approach. Before physical testing, virtual testing can be conducted to simulate the physical test. Virtual model of the full testing system including controller, actuators, and fixtures can be constructed and validated. In this work, an example has been developed and validated to show the potentials of the virtual testing process. Hybrid simulation is an approach of analyzing an analysis model and physical structure integrated system under realistic loading conditions. Hybrid simulation combines the lab testing with numerical analysis to explore the benefits of both methodologies. In this study, a hybrid simulation for a simplified airplane wing was conducted to demonstrate the process. Virtual testing and hybrid simulation are alternative methods of Testing Pyramid approach. Full scale tests are still required for certification but the more that is known about the test article, the greater chances of success in the full-scale certification testing. | virtual testing, hybrid simulation, reduced order model, cross coupling, ANSYS, Opensees, OpenFresco | 2019 | 1 | 11 | 1-10 | 10.2478/fas-2019-0001 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Wojciech Zieliński 1 Łukasz Piątkowski 1 Michał Dziendzikowski 1 Artur Kurnyta 1 Rafał Wrąbel 1 Tomasz Cichocki 1 Andrzej Leśniczak 1 Marcin Kurdelski 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Księcia Bolesława Street 6, 01-494 Warsaw, Poland | MI-24 HELICOPTER FULL SCALE FATIGUE TEST CONCEPT | This paper presents a general concept of the Full Scale Fatigue Test of the Mi-24 helicopter including the test layout and load distribution, as well as describes the milestones to be achieved. Additionally, some initial work conducted in order to determine both the mass and load distribution in the structure is described. The main goal of the test is to verify the low cycle fatigue life of the helicopter structure (fuselage, tail boom, wings and landing gear). The test will be divided into two main stages at which flight and landing loads will be applied. The authors demonstrate the general test concept, the helicopter’s structure fixture and the arrangement of the hydraulic actuators at both stages in order to achieve representative loads during the test. The proposed concept is based on AFIT’s previous experience in full scale structural testing, available literature and the experience of the test staff. | Full Scale Fatigue Test, Mi-24 helicopter | 2019 | 1 | 11 | 11-18 | 10.2478/fas-2019-0002 | Fatigue of Aircraft Structures |
| Dominik Nowakowski1 Marta Baran1 Janusz Lisiecki1 Sylwester Kłysz1,2 Piotr Synaszko1 | 1) Air Force Institute of Technology, ul. Księcia Bolesława 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury in Olsztyn, ul. Michała Oczapowskiego 2, 10-719 Olsztyn, Poland | EXAMINATION OF HONEYCOMB CORE COMPLIANCE IN SANDWICH STRUCTURE | The objective of the research presented in this paper was to determine the honeycomb core compliance of a sandwich structure of the horizontal stabilizer of the MiG-29 fighter jet in the static compression test. The study of the specimen was conducted based on the ASTM C365/C365M standard. The article presents the results of experimentally determined dependencies and strength parameters, i.e. the force-displacement dependence, the compressive modulus and the honeycomb core deformations. | honeycomb core, horizontal stabilizer, MiG-29 fighter jet, static compression test, compliance | 2019 | 1 | 11 | 19-27 | 10.2478/fas-2019-0003 | Fatigue of Aircraft Structures |
| Marta Baran1 Janusz Lisiecki1 Sylwester Kłysz1,2 Piotr Synaszko1 | 1) Air Force Institute of Technology, ul. Księcia Bolesława 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury in Olsztyn, ul. Michała Oczapowskiego 2, 10-719 Olsztyn, Poland | COMPARATIVE STUDY ON FATIGUE LIFE OF CFRP COMPOSITES WITH DAMAGES | In this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method. The tests were performed using the fixtures manufactured according to the ASTM D7137/7137M standard. The specimens were compressed to determine the residual strength. This value was afterwards used to specify the force levels for the fatigue tests. The fatigue tests were carried out under force control – with a sinusoidal shape, stress ratio R equal to 0.1 and frequency f 1Hz. Maximum force in a loading cycle Pmax was being increased after each thousand of cycles N until its value was close to the residual strength determined in the previously mentioned tests. In this work, the following relationships were presented: force-displacement P-δ for both static and fatigue tests and displacement-loading cycles δ-N for fatigue tests. A method of conducting the fatigue tests of CFRP composite was proposed, in which both the CAI specimens and CAI fixture were used. This allowed researchers to accelerate making initial comparisons between the two groups of specimens with damages – grouped relative to the way of conditioning. | CAI, CFRP, compression, Compression After Impact, damage, dropweight impact test, fatigue test, residual strengt | 2019 | 1 | 11 | 28-38 | 10.2478/fas-2019-0004 | Fatigue of Aircraft Structures |
| Łukasz Lindstedt 1 Mirosław Rodzewicz 1 Cezary Rzymkowski 1 Krzysztof Kędzior 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics plac Politechniki 1, 00-661 Warsaw, Poland | IMPACT LOADS AND CRASH SAFETY OF THE COCKPIT OF A COMPOSITE GLIDER | One major problem associated with gliding is the safety of the crew during landings in the country outside the airfield. The analysis of glider-accident statistics shows that such out-landings may significantly influence the safety. Therefore, of vital importance are the crashworthiness properties of the glider fuselage structure. The subject of the study was the PW-5 glider fuselage made of composites and subjected to high loads typical of glider crashes. The aim was to provide experimental data for validation of a numerical model of the cockpit-pilot system during impact. Two experimental tests with the composite glider cockpit were performed using a typical car-crash track. During the first test the cockpit with a dummy inside was crashed onto the ground at the angle of 45 degrees at a speed of 55 km/h. Accelerations and deformations at chosen points in the cockpit as well as signals coming from the dummy sensors and forces in the seat belts were recorded. The second test was an impact into a concrete wall at a speed of about 80 km/h. The full-scale tests were accompanied by a number of quasistatic and dynamic laboratory tests on samples of composite material. The experimental tests provided valuable results for the parametrical identification of a simulation model developed using the MADYMO software. | crash safety, composite glider, model experimental validation | 2019 | 1 | 11 | 39-55 | 10.2478/fas-2019-0005 | Fatigue of Aircraft Structures |
| Michał Sałaciński1 Rafał Kowalski2 Michał Szmidt3 Sławomir Augustyn4 | 1) Air Force Institute of Technology, Księcia Bolesława 6, 01-494 Warsaw, Poland 2) 41st Training Air Base, Brygady Pościgowej, 08-530 Dęblin, Poland 3) Łukasiewicz Research Network ‒ Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 4) Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | A NEW APPROACH TO MODELLING AND TESTING THE FATIGUE STRENGTH OF HELICOPTER ROTOR BLADES DURING REPAIR PROCESS | The fatigue test was carried out on an element of a rotor blade removed from the Mi-2 helicopter. The purpose of the test was to check the fatigue strength of the repaired rotor blade. Metal composite rotor blades have a metal spar in the form of a box and the trailing sections in the form of metallic honeycomb sandwich panels. The trailing sections are bonded to the spar. The repair had been carried out at the point where the trailing section became debonded from the spar at the Air Force Institute of Technology in Warsaw using a methodology developed for carrying out repairs of rotor blades’ damage. All types of the Mi family helicopters are equipped with metal composite rotors blades. Depending on MTOW (Maximum Take-Off Weight) and destination of helicopters, blades differ in dimensions, but their design solutions are practically the same. For this reason, the developed repair methodology can be used for all characteristic rotor blades structures for Mi helicopters. The fatigue test was performed at the Łukasiewicz - Institute of Aviation in Warsaw, using a hydraulically driven fatigue machine. The fatigue test was carried out by performing over 1.1 million load cycles. In repair places, upon completion of fatigue testing, no damage was found. | rotor blade, helicopter, fatigue test, repairs, bonding, composites | 2019 | 1 | 11 | 56-67 | 10.2478/fas-2019-0006 | Fatigue of Aircraft Structures |
| Rafał Luziński 1 Jarosław Ziemkiewicz 1 Piotr Synaszko 1 Andrzej Żyluk 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland | A COMPARISON OF COMPOSITE SPECIMENS DAMAGE AREA MEASUREMENTS PERFORMED USING PULSED THERMOGRAPHY AND ULTRASONIC NDT METHODS | Carbon fiber reinforced plastics (CFRPs) are widely used in aerospace structures due to their high stiffness, strength and good fatigue properties. They are however vulnerable to loads perpendicular to their plane and, while impacted, can suffer significant internal damage decreasing their overall strength. Detecting and sizing such damage is an important task of the non-destructive inspection (NDI) methods. This study was conducted to detect and quantify damage in a set of six impacted even rectangular CFRP specimens designed from a MiG-29 vertical stabilizer’s skin. The inspection was done using the ultrasonic (UT) method (based on mobile scanner – MAUS V) and the pulsed infrared thermographic (IRT) method. Each specimen’s inside and outside (impacted) surface was inspected separately with IRT, while the outside surface was then inspected with UT. UT provided the most precise measurements of the damage area, while the IRT inspection of the outside surface (which would be accessible on a real aircraft structure) provided underestimated values due to the damage’s depth and geometry. | NDT,NDI, ultrasonics, infrared thermography, CFRP, BVID, impact damage, composite structures | 2019 | 1 | 11 | 68-77 | 10.2478/fas-2019-0007 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Andrzej Michałowski 1 Sławomir Czarnewicz 1 | 1) Łukasiewicz Research Network – Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | DETERMINATION OF STRESS VALUES IN THE SURFACE LAYER OF INCONEL 718 SAMPLES DEDICATED TO FATIGUE TESTS | This work deals with the problem of X-ray stress determination on the samples dedicated to fatigue tests. A number of research studies point out the fact that the processing of hard, difficult to machine materials like nickel superalloys, reveals more than one trend of residual stress versus working parameters of behaviour (Lavella and Berruti, 2010). Many papers have shown that the residual stresses are dependent on a combination of a number of factors. When the above is taken into account simultaneously with the requirements of the internal General Electric specification for the fatigue tests samples preparation (Metallic test specimen preparation, low stress, 2017) the problem of turning and grinding parameters gathers significance. It is well known that the quality of the surface layer, produced during machining, is of vital importance for the fatigue life specially for the components of aircraft produced form nickel superalloys e.g. Inconel 718 (Kortabarri et al., 2011). That is why the surface layer’s properties are described in detail by the standards. The aim of the work is to determine one of the most influential features from the point of view of fatigue life, i.e. the stress state on the surface layer with one non-destructive method – the diffraction analysis. | turning, grinding, X-ray diffraction, stress analysis, Inconel 718 | 2019 | 1 | 11 | 78-86 | 10.2478/fas-2019-0008 | Fatigue of Aircraft Structures |
| Paulina Kamińska 1 Jarosław Ziemkiewcz 1 Piotr Synaszko 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland | COMPARISON OF PULSE THERMOGRAPHY (PT) AND STEP HEATING (SH) THERMOGRAPHY IN NON-DESTRUCTIVE TESTING OF UNIDIRECTIONAL GFRP COMPOSITES | This paper presents two techniques of active thermography i.e. the pulsed thermography technique and the step heating technique. The aim of this article is to compare these two techniques and present the possibilities, advantages and limitations of their use in the context of non-destructive testing of composite materials. The experimental section presents the results of tests carried out on samples of the polymer composites reinforced with glass fiber. | pulsed thermography, step-heating thermography, composites, NDT, NDE, GFRP | 2019 | 1 | 11 | 87-102 | 10.2478/fas-2019-0009 | Fatigue of Aircraft Structures |
| Krzysztof Stanisław Szafran 1 Ireneusz Kramarski 2 | 1) Łukasiewicz Research Network – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) HORNET, ul. Dębowa 72/33, 05-100 Nowy Dwor Mazowiecki, Poland | FATIGUE DEGRADATION OF THE RAM-AIR PARACHUTE CANOPY STRUCTURE | In this work, the authors continue researching issues related to fatigue of aircraft structures made of fabrics. Parachute systems are widely used in military, sport and recreational aviation. Braking parachutes as well as skydiving and troop parachutes are characterized by the repeated use of parachute canopies, which are exposed to wear and fatigue. Until now, parachutes were difficult to design aviation systems due to their complex and unsteady opening characteristics, large changes in the geometry of canopies, suspension lines and tape risers as well as exposure to stochastic atmospheric turbulence. The fatigue of the canopy fabric, suspension lines and tape risers is a problem that must be addressed by textile designers and designers of reusable parachute systems. The authors of this work demonstrate the complexity of operating a parachute in hard multiple use conditions and propose ways to extend the parachute’s service life without compromising safety. | parachute systems, aerodynamic decelerator, ram-air canopy, fatigue degradation, aviation safety | 2019 | 1 | 11 | 103-112 | 10.2478/fas-2019-0010 | Fatigue of Aircraft Structures |
| Andrzej Leski 1 | 1) Łukasiewicz Research Network – Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | IMPROVING THE ACCURACY OF FATIGUE DAMAGE CALCULATIONS FOR ARCHIVED DATA | Historical operational usage data give a ground for fatigue damage estimation. Quality of sensors and recorders two or more decades ago were lower then modern one. Lack of resolution in nz-level measurement and recording leads to some errors in fatigue damage calculations. In this paper author propose a method to improve the accuracy of fatigue damage calculations for archived data. The method takes advantage of typical distribution of accumulated cycles for aircrafts. Small correction in representative nz value taken in calculations can reduce the error in fatigue damage assessment. | Fatigue damage, nz, aircrafts, recorders, calculation, cycles, error | 2019 | 1 | 11 | 113-120 | 10.2478/fas-2019-0011 | Fatigue of Aircraft Structures |
| Błażej Morawski1 Dominik Głowacki1 Anna Głowacka2 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, plac Politechniki 1, 00-661 Warsaw, Poland 2) Warsaw University of Technology, Institute of Machine Design Fundamentals, plac Politechniki 1, 00-661 Warsaw, Poland | LOW-COST DATA ACQUISITION UNIT FOR FLIGHT TESTS | The purpose of this paper is to present the design of a data recorder for flight tests of a full-scale aircraft and an UAV. The recorder is built based on the Arduino microprocessor platform and LabVIEW development environment. The data recorder will be used mainly for helicopter flight tests. | helicopter flight test, LabVIEW, Arduino | 2019 | 1 | 11 | 121-130 | 10.2478/fas-2019-0012 | Fatigue of Aircraft Structures |
| Magdalena Czaban 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | AIRCRAFT CORROSION – REVIEW OF CORROSION PROCESSES AND ITS EFFECTS IN SELECTED CASES | From the safety point of view, one of the most important issues regarding aircraft operations is ensuring the durability of the structural components. Corrosion processes can have a significant effect on the integrity of structural materials and are usually associated with aircraft aging. Due to the variety of materials used, environments and loads impacting the planes, a wide range of different types of corrosion may occur in aircraft structures. The main aim of this study is to present some theoretical knowledge related to corrosion processes as well as problems of aircraft structures associated with corrosion occurrence. Firstly, the paper presents a brief overview of what corrosion is and what different types of corrosion are. Secondly, some selected aircraft failures caused by corrosion are shortly presented and discussed. | integrity of structure, corrosion processes, failures caused by corrosion | 2018 | 1 | 10 | 5-20 | 10.2478/fas-2018-0001 | Fatigue of Aircraft Structures |
| Małgorzata Zalewska 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | INFLUENCE OF THE FATIGUE LOAD LEVEL AND THE HOLE DIAMETER ON THE LAMINATE STRUCTURE’S FATIGUE PERFORMANCE | Damage tolerance of composite aircraft structure is one of the main areas of research, important when a new product is being developed. There are a number of variables, such as damage characteristics (dent depth, delamination area) and loading parameters (load type, amplitude of cyclic loading, load sequence) that need to be investigated experimentally [1]. These tests of composite materials are usually performed at an element level and are carried out in order to validate the analytical model, developed to predict the full-scale component’s behaviour. The paper presents the results of compression testing of the [36/55/9] carbon fibre/epoxy laminate, manufactured with the Automated Fibre Placement technology (AFP) and subjected to static and fatigue loads. The laminate compression loading mode was achieved through sandwich 4-point flexure. At the stage of fatigue testing, two parameters were investigated: the damage size, simulated by the hole diameter and the fatigue load level. Based on the test results, the laminate fatigue load limit equal to 75% of the OHC failure load was evaluated. By collating the static and fatigue tests results, the damage tolerance characteristic of the considered laminate was created. | composite, fatigue, damage | 2018 | 1 | 10 | 21-30 | 10.2478/fas-2018-0002 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska1 Andrzej Baczmański2 Sebastian Wroński2 Mirosław Wróbel3 Christian Scheffzük4,5 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland 2) AGH-University of Science and Technology, WFiIS, Kraków, Poland 3) AGH-University of Science and Technology, WIMiIP, Kraków, Poland 4) Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia 5) Karlsruhe Institute of Technology, AGW, Karlsruhe, Germany | THE HARDENING IN ALLOYS AND COMPOSITES AND ITS EXAMINATION WITH A DIFFRACTION AND SELF-CONSISTENT MODEL | The paper presents the results of diffraction stress measurement in Al/SiC composite and in 2124T6 aluminum alloy during the in situ tensile test. The main aim of the work is to observe the stress values for different stages of tensile test for the composite after applying two types of thermal treatment and for the alloy used as a matrix in this composite, to identify the type of hardening process. The experimental results were compared against the calculations results obtained from the self-consistent model developed by Baczmański [1] - [3] to gain the information about the micromechanical properties (critical resolved shear stress τcr and hardening parameter H) of the examined materials. This comparison allowed researchers to determine the role of reinforcement in the composite as well as the impact of the heat treatment on the hardening of the material. | metal-matrix composites (MMCs), hardening, micro-mechanics, neutron diffraction | 2018 | 1 | 10 | 31-46 | 10.2478/fas-2018-0003 | Fatigue of Aircraft Structures |
| Maciej Malicki 1 Kamil Sobczak 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | VERIFICATION OF THE COMPUTED TOMOGRAPHY RESULTS OF ALUMINUM ALLOY WELDED JOINT | Computed tomography (CT) of aluminum welded joint specimen has been performed. On the tomographic cross sections some defects have been found. To verify them the metallography cross sections of welded has been done. It was found that selected defects are micro cracks. | computed tomography (CT), welded joints, defects, micro cracks | 2018 | 1 | 10 | 47-52 | 10.2478/fas-2018-0004 | Fatigue of Aircraft Structures |
| Mariusz Kubryn1 Henryk Gruszecki1 Leszek Pieróg1 Jerzy Chodur1 Janusz Pietruszka1 Józef Brzęczek2 | 1) Polskie Zakłady Lotnicze Sp. z o.o., Mielec, Poland 2) Politechnika Rzeszowska, Rzeszów, Poland | THE FATIGUE LIFE OF CABLES IN AIRCRAFT FLIGHT CONTROL SYSTEMS | The cable flight control systems are commonly used for the control of small airplanes. In these systems, the cables are the only elements transmitting loads from the pilot to the control surfaces. During a flight the cables are moving through pulleys and are subjected to variable loads. A simple analysis of stress in the cable shows that the stress generated by the cyclical bending on the pulleys causes the fatigue of the wires. This phenomenon was noticed on a military aircraft of the M28 family during periodic maintenance inspection in 2007. The endurance tests of KSAN cables of the diameter equal to 3.5 mm and 1.8 mm were performed at the PZL MIELEC. The tests showed the limited fatigue life of the cables due to a progressive increase in the number of broken wires. | fatigue, cable flight control systems, cable endurance tests | 2018 | 1 | 10 | 53-62 | 10.2478/fas-2018-0005 | Fatigue of Aircraft Structures |
| Wojciech Wronicz 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | EXPERIMENTAL VALIDATION OF RIVETING PROCESS FE SIMULATION | Rivets are critical areas in metal airframes from the fatigue point of view. Fatigue behaviour of riveted joints depends strongly on the residual stress system around the rivet holes. The both most convenient and most common method of determining these stresses is the Finite Element (FE) analyses. The validation of models used is necessary to ensure the reliability of results. This paper presents the validation process of the riveting FE simulations for the universal and the countersunk rivets. At first, the material model of the rivets was validated with the use of the force–displacement curves of the press stamp obtained experimentally. Because of the displacement measurement method, it was necessary to take into account the flexibility of the stand. After that, good correlation between the numerical simulations and the experiment was obtained for both rivet types. At the second stage, strains around driven heads measured with the use of strip gauge patterns were compared with the results of the FE simulations. Quite good correlation was obtained for the countersunk rivet. In the case of the universal rivet, the numerical results are significantly higher values than the measured ones. Differences in correlation of the experiments and FE simulations for the analysed rivet types probably result from material differences of the rivets. | rivets, riveting process modelling, experimental validation | 2018 | 1 | 10 | 63-72 | 10.2478/fas-2018-0006 | Fatigue of Aircraft Structures |
| Angelika Wronkowicz-Katunin 1 | 1) Silesian University of Technology, Institute of Fundamentals of Machinery Design,Gliwice, Poland | A BRIEF REVIEW ON NDT&E METHODS FOR STRUCTURAL AIRCRAFT COMPONENTS | The paper presents a summary of non-destructive testing and evaluation (NDT&E) methods applied in inspections of structural aircraft components. This brief review covers the most commonly applied methods such as visual and penetrant inspections, tap-testing, eddy current inspections, shearography, thermography, acoustic emission testing, radiographic and tomographic inspections, and ultrasonic inspections. The general operating principles of these methods as well as their main advantages, limitations and application areas are described below. | NDT&E methods, non-destructive testing, non-destructive evaluation, aircraft structures, composite structures | 2018 | 1 | 10 | 73-81 | 10.2478/fas-2018-0007 | Fatigue of Aircraft Structures |
| Angelika Wronkowicz-Katunin1 Krzysztof Dragan2 | 1) Silesian University of Technology, Institute of Fundamentals of Machinery Design, Konarskiego 18A, 44-100 Gliwice, Poland 2) Air Force Institute of Technology, Laboratory of Non-Destructive Testing, Ks. Bolesława 6, 01-494 Warsaw, Poland | EVALUATION OF IMPACT DAMAGE IN COMPOSITE STRUCTURES USING ULTRASONIC TESTING | Barely visible impact damage is one of the problems commonly occurring in composite elements during an aircraft operation. The authors described the mechanisms of impact damage formation and propagation in composite structures. The paper presents a performed analysis of an influence of impact parameters on the resulting damage, i.e. its detectability by means of visual observation as well as its extent determined based on ultrasonic tests results. The tests were conducted on the CFRP specimens with a wide range of impact damage cases obtained with combinations of variable impact energy and shapes of impactors. Additionally, an algorithm based on image processing and image analysis methods is proposed for the purpose of the effective evaluation of the ultrasonic data obtained. | impact damage, composite structures, non-destructive testing, ultrasonic testing, image analysis | 2018 | 1 | 10 | 82-92 | 10.2478/fas-2018-0008 | Fatigue of Aircraft Structures |
| Krzysztof Stanisław Szafran 1 Ireneusz Kramarski 2 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) HORNET, ul. Dębowa 72/33, 05-100 Nowy Dwor Mazowiecki, Poland | FATIGUE DEGRADATION OF THE STRUCTURE OF PARACHUTE SYSTEMS | Parachute systems are in widespread use in aviation. Up to now, parachutes are the most uncertain air vehicles because of their complex and unsteady opening characteristics, changes in geometry up to 30% and vulnerability from unsteady atmospheric turbulence. Fatigue is a problem that the designers of long living parachute systems need to cope with. Authors demonstrate complexity of parachute exploitation and means to lower opening forces and extend service life without influencing safety. | Parachute systems, fatigue degradation, aviation safety system | 2018 | 1 | 10 | 93-103 | 10.2478/fas-2018-0009 | Fatigue of Aircraft Structures |
| Krzysztof Szafran1 Nikolaj Delas2 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) National Aviation University, Kyiv, Ukraine | ACCUMULATION OF FATIGUE MICRODEFECTS – ENTROPY INTERPRETATION | The authors of the paper presented some of the models describing the process of micro-cracks’ development. In this study, the process of a selected model of micro-cracking was analyzed. In the model it was assumed that the damage to the material has some “thermodynamic properties” or rather universal properties inherent in most complex systems. In order to calculate the long-term fatigue strength properties of a structure, it is important to have a good understanding of the distribution parameters of the number of defects of different sizes. A model was built using the entropy principle, which is effectively used to test complex systems that are difficult to formalize. As a result of many experimental studies it was found that the development of fatigue damage is closely related to the process of plastic deformation of the material at the contact point of local defects. The results of computer calculations and simulations led to the conclusions presented in the final part of this paper. | distribution of microcracks, entropy interpretation of microcracks, fatigue curve formula | 2018 | 1 | 10 | 104-116 | 10.2478/fas-2018-0010 | Fatigue of Aircraft Structures |
| Andrzej Katunin 1 Michał Zuba 1 | 1) Institute of Fundamentals of Machinery Design, Silesian University of Technology, Konarskiego 18A, 44-100 Gliwice, Poland | Identification of Delamination in Composite Beams Using the Fractal Dimension-Based Damage Identification Algorithm | Damage detection and identification is one of the most important tasks of proper operation of technical objects and structures. It is, therefore, essential to develop efficient and sensitive methods of early damage detection. Delamination is the type of damage occurring in laminated composites that is one of the most dangerous and most difficult to detect. In this paper, the computational study was performed on the numerical data of the modal shapes of laminated composite beams with simulated delaminations in order to detect them using a fractal dimension-based approach. The obtained results allowed for improvement of detection accuracy as compared to previously applied wavelet-based approach. An additional benefit was decreasing the computational time. Basing on the obtained results it is reasonable to consider the presented approach as a promising alternative to currently applied signal processing methods used for supporting nondestructive testing of structures. | structural damage identification, fractal dimension, non-destructive testing, composite structures, delamination | 2017 | 1 | 9 | 5-16 | 10.1515/fas-2017-0001 | Fatigue of Aircraft Structures |
| Andrzej Leski1 Michał Szmidt1 Piotr Synaszko2 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Air Force Institute of Technology, Ks. Bolesława 6, 01-494 Warsaw, Poland | Localization of Sound Sources during Full Scale Fatigue Test of the Vertical Stabilizer with the Acoustic Holography Technique | An acoustic holography and its practical applications in engineering began to develop at the end of the 20th century. Currently, this technique is being commonly used to locate sound sources. This paper presents the use of an acoustic camera to locate sound sources during the Full Scale Fatigue Test of the MiG-29 stabilizer. During fatigue tests, the tested structure issues a series of sounds in the form of glitches, creaks or beats. These sounds are typical for a structure subjected to dynamic loading, but they can also be a source of diagnostic information about places of fatigue failures. The paper presents the results of measurements made during the fatigue test. Thanks to the analysis of the measurement results, it was possible to identify areas that are the basic source of sounds. | holography, Full Scale Fatigue Test, damage detection, microphone arrays | 2017 | 1 | 9 | 17-25 | 10.1515/fas-2017-0002 | Fatigue of Aircraft Structures |
| Bartosz Madejski 1 Grzegorz Socha 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | Calibration of the Ductile Failure Criterion for Nickel-Based Superalloys Taking into Account the Localization of the Strain | Static tension test allows characterization of material strength properties. This simple test provides input data for numerical calculation of structural components made of the tested alloy. Elastic, plastic and failure behavior of the structural component in question is simulated, using, for example, the FEM package, based on parameters obtained as the result of tensile testing. When using the results of the tensile test for modeling the material failure it is important to estimate correctly plastic strain corresponding to failure. It is common practice to use elongation of the specimen gage part for the calculation of failure strain. On the other side, the most popular ductile failure criterion used by engineers performing numerical simulation of the material’s behavior relies on the equivalent plastic strain as the criterial quantity. Those two parameters can differ significantly. In order to calculate the equivalent plastic strain correctly, we have to remember about strain localization (necking) appearing during tensile tests and take into account the fact that during tensile testing we have three non-zero strain tensor components. Ignoring this fact, and using only elongation as the criterial quantity can lead to enormous simulation error. This error is analyzed in this paper for nickel based superalloy tested at elevated temperatures. | equivalent plastic strain, tensile test, failure criterion | 2017 | 1 | 9 | 27-37 | 10.1515/fas-2017-0003 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 | 1) Institute of Aviation, Materials and Structures Research Center, al. Krakowska 110/114, 02-256 Warszawa, Poland | Methods for Different Orders Stresses Estimation with Diffraction Methods | The publication describes how diffraction methods and mathematical bases can be used for measurement of various types of stresses in single-phase and multiphase materials. Firstly, the paper defines the stresses and classifies them from the scale of their interactions point of view. Subsequently, the phenomenon of radiation diffraction on the crystalline lattice is presented including formulas describing this phenomenon and the dependencies enabling stress measurements. The key part of the paper is the description of one of the second order stress estimation methods based on diffraction data and a selfconsistent model. | stress, diffraction methods for stress estimation, orders of stresses. | 2017 | 1 | 9 | 39-54 | 10.1515/fas-2017-0004 | Fatigue of Aircraft Structures |
| Marcin Zapłotny1 Andrzej Katunin1 Krzysztof Dragan2 | 1) Institute of Fundamentals of Machinery Design, Silesian University of Technology, Konarskiego 18A, 44-100 Gliwice, Poland 2) Air Force Institute of Technology, Ks. Bolesława 6, 01-494 Warsaw, Poland | Enhancement of Damage Detectability in Aircraft Structures using the Fusion of NDT Results | Following the damage tolerance philosophy in aircraft design and operation, one of the most significant stages of maintenance is non-destructive testing of structures. It is, therefore, essential to use testing methods sensitive to particular damage types occurring in aircraft structures during operation. In this paper, the authors present a study on selection and comparison of methods of information fusion applied to testing the results of inspection of composite structures used in aircraft elements, obtained using various ultrasonic methods. The presented approach of fusion of ultrasonic scans allows for enhancement of damage detection and identification due to the presence of different parts of information about detected damage obtained from different initial information sources in a single resulting set. Such an approach can be helpful at the decision-making stage during inspection of aircraft elements and structures. Besides the methodology, the GUI-based software for performing fusion of various types of ultrasonic data is presented. | aircraft composite structures, ultrasonic testing, information fusion, non-destructive testing | 2017 | 1 | 9 | 55-74 | 10.1515/fas-2017-0005 | Fatigue of Aircraft Structures |
| Marek Rośkowicz 1 Piotr Leszczyński 1 | 1) Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | Evaluation of the Suitability of the Strain-Gauge Method for Measuring Deformations During the Fatigue Tests of Avi ation Composite Structures | The paper discusses the results of selected fatigue tests of a motor glider’s insulated spar structure. The results of the experimental tests were used to assess the potential of the strain-gauge method for diagnosing the spar damage involving the unbolting of one of metal fittings in the spar pin. The usefulness of the deformation measurement method in the composite structure diagnostic process was confirmed, while simultaneously drawing attention to the need for conducting a process optimizing the number of sensors and their distribution on a tested object, in the context of the sensitivity of diagnostic signals received. | aviation composite structures, fatigue tests, strain-gauge method, deformation measurements. | 2017 | 1 | 9 | 75-84 | 10.1515/fas-2017-0006 | Fatigue of Aircraft Structures |
| Mateusz Fałek 1 Elżbieta Szymczyk 1 Jerzy Jachimowicz 1 | 1) Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | Study on Possible Replacement of the Aluminum Spar with a Composite Structure Illustrated with the Case of Agricultural Aircraft | Composite materials are increasingly being used in aviation. Specific stiffness and strength of composite materials (especially CFRP laminate, sandwich structure) are higher compared to metal alloys. They are beneficial features of materials used in aviation. Mass reduction of aircraft structures (e.g. due to the use of composite materials) contributes to an aircraft’s better performance in terms of its range, top speed and ceiling and consequently causes an increase in airplanes capacity. Moreover, the use of high-strength and lightweight materials in aviation contributes to longer life time and lower exploitation costs. The aim of the paper was the study the possibilities of replacing the aluminum spar of an airplane wing with a composite structure. In order to compare the mass and strength of the aluminum with the composite spar, the global shell and local solid models were created and finite elements analysis was performed. The analysis was carried out for the front spar of the wing of the agricultural aircraft PZL-106. | brak | 2017 | 1 | 9 | 85-99 | 10.1515/fas-2017-0007 | Fatigue of Aircraft Structures |
| Piotr Reymer1 Marcin Kurdelski1 Andrzej Leski2 Andrzej Leśniczak1 Michał Dziendzikowski1 | 1) Air Force Institute of Technology, Ks. Bolesława 6, 01-494 Warsaw, Poland 2) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | Introduction of an Individual Aircraft Tracking Program for the Polish Su-22 | The Su-22 fighter-bomber is a military aircraft used in the Polish Air Force (PLAF) since the mid 1980’s. By decision of the Ministry of National Defence Republic of Poland, the assumed service life for this type of aircraft was prolonged up to 3200 flight hours based on the Full Scale Fatigue Test (FSFT) results. The FSFT was conducted using the real load profile defined during the Operational Load Monitoring Program (OLM) and the 3200 hour service life was also based on this load profile. In order to assure safe operation of all the 18 Su-22 aircraft, the Individual Aircraft Tracking program was introduced. The program was based on the results of the FSFT as well as the analysis of the flight parameters recorded by the THETYS onboard flight recorder. In this paper, the authors present the methodology, assumed fatigue hypothesis and preliminary results of the IAT program for the Polish Su-22. | Individual Aircraft Tracking, Su-22 fighter-bomber | 2017 | 1 | 9 | 101-108 | 10.1515/fas-2017-0008 | Fatigue of Aircraft Structures |
| Shashidhar K Kudari1 C. M. Sharanaprabhu2 | 1) Department of Mechanical Engineering, CVR. College of Engineering, Hyderabad, India 2) Department of Mechanical Engineering, PES ITM, Shivamogga, Karnataka, India | The Effect of Anodizing Process Parameters on the Fatigue Life of 2024-T-351-Aluminium Alloy | The effect of an anticorrosive layer on the fatigue life of 2024-T-351-aluminium alloy has been studied in the present investigation. The fatigue tests were conducted on the aluminium alloy with and without anodizing to evaluate the fatigue life. The results indicate that the fatigue life of the anodized specimens is significantly shorter than that of untreated specimens. Further, experiments were conducted to evaluate the effect of the anodizing process parameters on the fatigue life of anodized specimens. These results show that the fatigue life of anodized aluminium alloy can be improved by controlling the anodizing process parameters such as process temperature, voltage, and time of immersion. | aluminium alloy, fatigue, corrosion, oxidation, anodizing | 2017 | 1 | 9 | 109-115 | 10.1515/fas-2017-0009 | Fatigue of Aircraft Structures |
| Tayeb Kebir1 Mohamed Benguediab1 Abdellatif Imad2 | 1) Department of Mechanical Engineering, Faculty of Technology, Laboratory of Materials and Reactive Systems (LMRS), University of Sidi Bel-Abbes, Algeria 2) Polytech’Lille1, Laboratory of Mechanical of Lille (LML), University of Lille1, France | A Model for Fatigue Crack Growth in the Paris Regime under the Variability of Cyclic Hardening and Elastic Properties | Over the last 60 years, several models have been developed governing different zones of fatigue crack growth from the threshold zone to final failure. The best known model is the Paris law and a number of its based on mechanical, metallurgical and loading parameters governing the propagation of cracks. This paper presents an analytical model developed to predict the fatigue crack propagation rate in the Paris regime, for different material properties, yield strength (σy), Young’s modulus (E) and cyclic hardening parameters (K’, n’) and their influence by variability. The cyclic plastic deformation at a crack tip or any other cyclic hardening rule may be used to reach this objective, for to investigate this influence, these properties of the model are calibrated using available experimental data in the literature. This FCGR model was validated on Al-alloys specimens under constant amplitude load and shows good agreement with the experimental results. | cyclic plastic strain, elastic properties, cyclic hardening parameters, Young’s modulus, variability, crack tip, fatigue crack growth, constants of the Paris law, Al-alloys | 2017 | 1 | 9 | 117-135 | 10.1515/fas-2017-0010 | Fatigue of Aircraft Structures |
| Wojciech Wdowiński1 Elżbieta Szymczyk2 Jerzy Jachimowicz3 Grzegorz Moneta4 | 1) Ansaldo Energia, Switzerland 2) Military University of Technology, Warsaw, Poland 3) Military University of Technology, Warsaw, Poland 4) Ansaldo Energia, Switzerland | Design and Strength Analysis of Curved-Root Concept for Compressor Rotor Blade in Gas Turbine | The motivation of the article is fatigue and fretting issue of the compressor rotor blades and disks. These phenomena can be caused by high contact pressures leading to fretting occurring on contact faces in the lock (blade-disk connection, attachment of the blade to the disk). Additionally, geometrical notches and high cyclic loading can initiate cracks and lead to engine failures. The paper presents finite element static and modal analyses of the axial compressor 3rd rotor stage (disk and blades) of the K-15 turbine engine. The analyses were performed for the original trapezoidal/dovetail lock geometry and its two modifications (new lock concepts) to optimize the stress state of the disk-blade assembly. The cyclic symmetry formulation was used to reduce modelling and computational effort. | finite element method, turbine engine, rotor disk, rotor blades, blade-disc connection, shape optimization | 2017 | 1 | 9 | 137-155 | 10.1515/fas-2017-0011 | Fatigue of Aircraft Structures |
| Wojciech Wronicz 1 Jerzy Kaniowski 1 Maciej Malicki 1 Paweł Kucio 1 Robert Klewicki 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | Experimental and Numerical Study of NACA and Conventional Riveting Procedure | Fatigue behaviour is one of the most important properties of modern airplanes and rivets influence it strongly. According to the literature, the NACA riveting offers a multiple increase in the fatigue life of joints. The aim of this paper is to investigate the benefits offered by the NACA riveting procedure with respect to the residual stress and strain distribution after riveting as well as rivet hole expansion. Experimental and numerical approaches were adopted. The conventional riveting with both the universal and countersunk rivets was compared with the NACA riveting. The countersunk angle and depth in the case of the NACA riveting was modified somewhat relative to the values met in the literature. For these three cases, strain gauge measurements during riveting, hole expansion measurements and FE calculations were performed. The hole expansion measurement with the use of Computer Tomography(CT) was proposed. Only the FE calculations unambiguously indicate better fatigue properties of the NACA riveting. The proposed method of hole expansion measurement requires further research to increase its accuracy. | rivet, NACA riveting, fatigue, hole expansion, computed tomography | 2017 | 1 | 9 | 157-170 | 10.1515/fas-2017-0012 | Fatigue of Aircraft Structures |
| Antoni Niepokólczycki1 Andrzej Leski2 Krzysztof Dragan2 | 1) Institute of Aviation, Al. Krakowska 110/114, Warsaw, Poland 2) Air Force Institute of Technology, ul. Księcia Bolesława 6, 01-494 Warsaw, Poland | REVIEW OF AERONAUTICAL FATIGUE INVESTIGATIONS IN POLAND (2013-2014) | This review was presented on the 34 Conference of the International Committee on Aeronautical Fatigue and Structural Integrity, Helsinki, Finland, June 1-2, 2015. It contains description of main works and investigations in fatigue of aircraft structures performed in Poland during the years 2013 and 2014. | fatigue of aircraft structures | 2016 | 1 | 8 | 5-48 | 10.1515/fas-2016-0001 | Fatigue of Aircraft Structures |
| Andrzej Katunin 1 | 1) Institute of Fundamentals of Machinery Design, Silesian University of Technology, Konarskiego 18A, 44-100 Gliwice, Poland | LIGHTNING STRIKE PROTECTION OF AIRCRAFT COMPOSITE STRUCTURES: ANALYSIS AND COMPARATIVE STUDY | Lightning strikes are a serious problem during operation of aircraft due to the increasing applicability of polymeric composites in aircraft structures and the weak electrical conducting properties of such structures. In composite structures, lightning strikes may cause extended damage sites which require to be appropriately maintained and repaired leading to increased operational costs. In order to overcome this problem various lightning strike protection solutions have been developed. Some of them are based on the immersion of metallic elements and particles while others use novel solutions such as intrinsically conductive polymers or other types of highly conductive particles including carbon nanotubes and graphene. The concept of fully organic electrically conductive composites based on intrinsically conductive polymers is currently being developed at the Silesian University of Technology. The results obtained in numerous tests, including concerning electrical conductivity and the capability to carry on high-magnitude electrical charges as well as certain operating properties need to be compared with existing solutions in lightning strike protection of aircraft. The following study presents the properties of the material developed for lightning strike protection and a comparative study with other solutions. | lightning strike protection, conductive composite, aircraft structures | 2016 | 1 | 8 | 49-54 | 10.1515/fas-2016-0002 | Fatigue of Aircraft Structures |
| Józef Krysztofik 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | EVALUATION OF DAMAGE DEGREE OF INCONEL 718 USING NONDESTRUCTIVE INDICATORS OF DAMAGE | This paper presents the results of the quantitative evaluation of the degree of damage caused by plastic strain accumulated in static tensile tests and creep tests. To detect changes in the structure of the material and in order to determine the degradation of the materials, nondestructive methods were used, namely the ultrasonic and eddy current methods. In ultrasonic testing, attenuation and acoustic birefringence were used as damage indicators. In the case of the eddy current method, changes in the phase angle of impedance were observed in the material. The material tested was Inconel 718 alloy. Inconel alloys are often find application in extreme working conditions including in the power engineering industry, aviation and aerospace. A new type of specimen with the variable cross-sectional area of the measuring part was used in the tests. This allowed researchers to obtain a continuous distribution of plastic strain and enabled analysis of the material with respect to different damage degrees. The correlation between the degree of damage, expressed by the measure of deformation, and the value of nondestructive indicators was determined. On the basis of it, the dependence indicating the ability to nondestructive evaluation of the degradation degree of the material, subjected to loads exceeding the yield limit was obtained. | damage parameter, nondestructive testing, Inconel 718 | 2016 | 1 | 8 | 55-64 | 10.1515/fas-2016-0003 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, al. Krakowska 110/114, 02-256 Warszawa, Poland | ELECTROPOLISHING PROCEDURE DEDICATED TO IN-DEPTH STRESS MEASUREMENTS WITH X-RAY DIFFRACTOMETRY | Electropolishing is the sole reliable method of removing the outer layer of the specimen without changing its stress state. This feature of the electropolishing procedure allows researchers to investigate the in-depth stress distribution. Developing of the method in a diffraction laboratory is crucial because there is no universal theory for the electropolishing procedure allowing the removal of the layers of different thickness. This is due to the multiplicity of different factors affecting the electropolishing results. A factor of vital importance from the point of view of indepth stress measurements is the thickness of the electropolishing layer. Hence the importance of the procedures for the electropolishing of a layer of a precisely defined thickness. This work deals with the problem of the selection of the parameters in the electropolishing process for two types of materials: stainless steel and aluminium alloy. The tests of mutual correlation of current intensity, voltage applied and time of the procedure and its results are presented in the paper. | In-Depth stress distribution, Electropolishing, Diffraction methods | 2016 | 1 | 8 | 65-72 | 10.1515/fas-2016-0004 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Wojciech Wronicz 1 Maciej Malicki 1 | 1) Institute of Aviation, Materials and Structures Research Center, al. Krakowska 110/114, 02-256 Warszawa, Poland | THE IN-DEPTH STRESS DISTRIBUTION FOR 1H13 SPECIMEN AFTER CUTTING | Measuring the in-depth stress state is of vital importance for materials scientists. Strain gauges methods are capable of yielding information only about the surface stress state. Diffraction methods using synchrotron or neutron radiation, which allow totally non-destructive stress measurements inside the material, are not widely available. In this context, the best widely available method combines the X-ray diffraction stress measurements and gradual removal of the outer layer by means of electropolishing. Here, this method was applied to the specimen made of 1H13 stainless steel cut with under water on a corundum cut-off wheel. The idea was to investigate how deeply an additional stress state resulting from cutting was introduced and whether the technique of combining of X-ray diffractometry and electropolishing can be used widely for determining the stress state inside the specimen. | Depth stress distribution, Electropolishing, Diffraction methods, 1H13 stainless steel. | 2016 | 1 | 8 | 73-79 | 10.1515/fas-2016-0005 | Fatigue of Aircraft Structures |
| E. Gadalińska1 A. Baczmański2 Y. Zhao3 L. Le Joncour3 S. Wroński2 B. Panicaud3 M. Francois3 C. Braham4 T. Buslaps5 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) AGH-University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Kraków, Poland 3) ICD-LASMIS, Université de Technologie de Troyes (UTT), UMR CNRS 6281, rue Marie Curie, CS 4206, 10004 Troyes, France 4) PIMM, Arts et Métiers ParisTech (ENSAM), 151 Bd de l’Hôpital 75013 Paris, France 5) ESRF, 6 rue J. Horowitz, 38500 Grenoble Cedex, France | ADVANCED DEFORMATION STAGES IN DUPLEX STEEL INVESTIGATED USING NEUTRON AND SYNCHROTRON RADIATION | The grain scale of materials is an area still open for investigations within the field of materials science. The most helpful tools to perform this type of research are diffraction methods. Within the research project presented in this paper two experiments were carried out employing two different types of radiation: neutron (ISIS) and synchrotron (ESRF). The aim of the work was to describe the stress state in the necking zone during the occurrence of a damage phenomenon (Fig. 1.) in separate phase and to check the level of the homogeneity. The supplemental tools were the finite elements method and self-consistent modeling – it testified, confirmed and completed our experimental results and allowed us to formulate the justifiable conclusions. | Two-Phases materials, Mechanical behaviour, Diffraction methods | 2016 | 1 | 8 | 80-91 | 10.1515/fas-2016-0006 | Fatigue of Aircraft Structures |
| Maciej Malicki 1 Elżbieta Gadalińska 1 Maciej Chmiel 1 | 1) Institute of Aviation, Materials and Structures Research Center, al. Krakowska 110/114, 02-256 Warszawa, Poland | THE IMPACT OF DAMAGE IN ANNELING INCONEL 718 ON HARDNESS MEASURED BY THE VICKERS METHOD | In the previous work [1] it was shown that strain hardening had considerable impact on the hardness of Inconel 718. In order to verify the weakening of the material associated with the damage mechanism in the tested material, the hardness tests were performed on the stretched specimen which was subsequently heat treated. The tests revealed that, after heat treatment, the measured hardness was reduced with an increasing degree of the plastic deformation present prior to heat treatment. | Damage parameter, Vickers hardness, Inconel 718, Tensile test, Heat treatment | 2016 | 1 | 8 | 92-96 | 10.1515/fas-2016-0007 | Fatigue of Aircraft Structures |
| Dominik Głowacki 1 Mirosław Rodzewicz 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | THE ELABORATION OF THE METHOD OF FATIGUE TESTING OF THE ROTOR OF THE MOSUPS PLANE PROPULSION SYSTEM | This paper concerns fatigue testing of the rotor of the propulsion system for the MOSUPS – an unmanned aircraft designed in a joint wing configuration, and equipped with a ducted propeller. The work presents the analysis of the stresses and deformations of the rotor structure as well as the form of the loading cycle. The aim of the paper is to introduce the concept of a simplified method of fatigue testing of multi-blade rotors. With the sophisticated geometry of the rotor in mind – the authors applied the FEM tools and implemented the ANSYS and nCode programs. The prototype of the fatigue stand built by the authors is also presented in the paper. | UAV, Propulsion system, Stress analysis, Fatigue tests | 2016 | 1 | 8 | 97-103 | 10.1515/fas-2016-0008 | Fatigue of Aircraft Structures |
| Michał Sałacinski1 Andrzej Leski2 Michał Stefaniuk1 | 1) Air Force Institute of Technology, Ksiecia Boleslawa 6 street, 01-494 Warsaw, Poland 2) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | APPROACH TO CRITICAL CRACK OPENING DISPLACEMENT MODELING OF DAMAGE IN METAL SHEETS AFTER COMPOSITE PATCH BONDED REPAIR | The paper proposes a method of calculating the maximum displacement in the aircraft metal structure repaired by CPBR (bonded composite patch repair). The calculations were made based on specimens. The specimens were prepared according to the current requirements used in aviation. The 2024-T3 alloy metal sheet was a structure. To repair the structure used the boron-epoxy composite patch in prepreg technology was used. The metal structure was modeled as an isotropic elastic body. The metal structure coated with the composite patch was modeled as an orthotropic structure. Based on this, the stress was determined in the metal structure. The size opening displacement in the metal structure was determined based on the model of linear elastic fracture mechanics for the plane stress state. The calculation results were verified by measuring the displacement in laboratory conditions. The laboratory tests made it possible to demonstrate the accuracy of the proposed approach. | composites, aerospace, composite patch bonded repair | 2016 | 1 | 8 | 104-110 | 10.1515/fas-2016-0009 | Fatigue of Aircraft Structures |
| Michal Dziendzikowski 1 Slawomir Klimaszewski 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | FATIGUE CRACKS DETECTION USING PZT TRANSDUCERS UNDER THE INFLUENCE OF UNCERTAIN ENVIRONMENTAL FACTORS | This paper presents technique for qualitative assessment of fatigue crack growth monitoring, utilizing guided elastic waves generated by the sparse PZT piezoelectric transducers network in the pitch – catch configuration. Two Damage Indices (DIs) correlated with the total energy received by a given sensor are used to detect fatigue cracks and monitor their growth. The indices proposed carry marginal signal information content in order to decrease their sensitivity with respect to other undesired non-controllable factors which may distort the received signal. The reason for that is to limit the false calls ratio which besides the damage detection capability of a system, plays a crucial role in applications. However, even such simplified damage indices can alter over a long term, leading to the misclassification problem. Considering a single sensing path, it is very difficult to distinguish whether the resultant change of DIs is caused by a damage or due to decoherence of these DIs. Therefore, assessment approaches based on threshold levels fixed separately for DIs obtained on each of the sensing paths, would eventually lead to a false call. An alternative approach is to compare changes of DIs for all sensing paths. Developing damage distorts the signal only for the sensing paths in its proximity. In order to decrease the misclassification risk, a method of compensating such DIs drift is proposed. The main features and damage detection capabilities of this method will be demonstrated by conducting a laboratory fatigue test of an aircraft panel. The proposed approach has been verified on a real structure during fatigue test of a helicopter tail boom. | Structural Health Monitoring, PZT transducers, fatigue cracks detection, environmental factors compensation | 2016 | 1 | 8 | 111-115 | 10.1515/fas-2016-0010 | Fatigue of Aircraft Structures |
| Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | COMPARISON OF RESIDUAL STRESS STATE ON SHEETS FAYING SURFACE AFTER STANDARD AND NACA RIVETING-NUMERICAL APPROACH | One crucial characteristic of the aircraft structure are fatigue properties and rivets are usually critical areas in metal airframes due to fatigue cracks nucleation. According to literature, the NACA riveting method offers a huge increase in fatigue life of riveted lap joints. This paper presents FE simulations of quasi-static riveting on a press for standard countersunk rivets and the NACA riveting in two configurations: with a normal brazier rivet and a brazier rivet with a compensator. The analyzed configurations have been compared based on the stress courses on the sheets faying surfaces after riveting process. Due to a lack of data, the rivet length and the squeezing force value were assumed for NACA riveting based on FE simulations. The results indicated beneficial influence of the NACA riveting in the outer sheet (with a countersunk) and disadvantageous influence in the inner sheet. This effect was stronger in the case of the rivet with a compensator. | NACA riveting, fatigue, FE, joints | 2016 | 1 | 8 | 116-126 | 10.1515/fas-2016-0011 | Fatigue of Aircraft Structures |
| Józef Krysztofik 1 Wojciech Manaj 1 Grzegorz Socha 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | THE APPLICATION OF ACOUSTIC ANISOTROPY TO EVALUATION OF MATERIAL PROPERTIES | Structural properties of materials change under stress, temperature and work environment. These changes are generally unfavorable. They cause a reduction in strength of materials. This has an impact on the safety and service life of machines and constructions. In the chemical and petrochemical industry the destruction of a structure can be activated by chemical substances. In the energy industry, a key element in assisting the destruction is temperature. In aviation, the typical cause of damage is the process of fatigue. Regardless of the differences regarding/concerning the mechanisms of degradation, typical of the sectors of industry, the end result is the emergence of microvoids and microcracks in the material. In the final phase of the process, dominant cracks are formed. The term of measure of material damage, introduced by Kachanov and Rabotnow, can be effectively used also when considering the impact of microdamages on measurable macroscopic acoustic quantities. A damage parameter proposed by Johnson allows to correlate changes in acoustic birefringence of the material with the parameter describing the degree of damage. In this article the authors presented the nondestructive tests results concerning Inconel 718 alloy subjected to damage caused by plastic deformation. This paper focuses on the evaluation of acoustic properties in relation to the degradation of the materials tested. | nondestructive testing, acoustic birefringence, damage parameter, Inconel 718 | 2015 | 1 | 7 | 5-11 | 10.1515/fas-2015-0001 | Fatigue of Aircraft Structures |
| Krzysztof Dragan1 Michał Dziendzikowski1 Artur Kurnyta1 Michal Salacinski1 Sylwester Klysz1,2 Andrzej Leski1 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury, ul. Oczapowskiego 2, 10-719 Olsztyn, Poland | COMPOSITE AEROSPACE STRUCTURE MONITORING WITH USE OF INTEGRATED SENSORS | One major challenge confronting the aerospace industry today is to develop a reliable and universal Structural Health Monitoring (SHM) system allowing for direct aircraft inspections and maintenance costs reduction. SHM based on guided Lamb waves is an approach capable of addressing this issue and satisfying all the associated requirements. This paper presents an approach to monitoring damage growth in composite aerospace structures and early damage detection. The main component of the system is a piezoelectric transducers (PZT) network integrated with composites. This work describes sensors’ integration with the structure. In particular, some issues concerning the mathematical algorithms giving information about damage from the impact damage presence and its growth are discussed. | structural health monitoring, PZT sensor network, barely visible impact damage | 2015 | 1 | 7 | 12-17 | 10.1515/fas-2015-0002 | Fatigue of Aircraft Structures |
| Daniel K. Dębski 1 | 1) Warsaw University of Technology, Narbutta 84 Street, 02-524 Warsaw, Poland | NONLINEAR FATIGUE DAMAGE ACCUMULATION | One important element of any computational fatigue analysis is the adoption of a hypothesis of fatigue damage accumulation. The most commonly used is the hypothesis of linear accumulation of fatigue damage called the Palmgren-Miner hypothesis. This linear hypothesis does not take into account a factor of great importance: the mutual influence of consecutive fatigue load sequences on each other. In the presented paper, only two consecutive load sequences linked by mutual relations have been analyzed and the results of the analysis have been shown. A more complex form which takes into account the full load history would create complex formula difficult to use. Perhaps, we should go in this direction, especially that today we have enormous computing power at our disposal. | cumulative fatigue damage; fatigue damage accumulation; cumulative damage rules; load interaction effects; fatigue life prediction | 2015 | 1 | 7 | 18-23 | 10.1515/fas-2015-0003 | Fatigue of Aircraft Structures |
| Piotr Synaszko 1 Michał Sałaciński 1 Łukasz Kornas 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE EFFECT OF ENVIRONMENTAL FLIGHT CONDITIONS ON DAMAGE PROPAGATION IN COMPOSITE SANDWICH STRUCTURE | The aim of the study was to determine the traceability of damage growth caused by inclusions of water in the composite sandwich structure. It was assumed that as a result of temperature changes during the flight and accompanying phase transformation, the zone containing water inclusions increases. The growth is caused by the destruction (mainly the tearing of walls) of the core. As part of the work, this assumption was verified experimentally. For the experiment to be successful it was necessary to simulate actual flight conditions. The simulation involved inducing phase transformations of water in the core cell as a function of time and temperature. Before and after the experiments the non-destructive tests using pulsed thermography were performed. The test results revealed an increase in the number of cells occupied by water. Adequate specimens were designed and manufactured. The study showed that cyclical changes in temperature affected the propagation of water in core sandwich structures. Further, it was found that the increase in the surface area of water-containing inclusions could be monitored using thermographic techniques. | honeycomb structures, detection of water ingress, thermografic techniques | 2015 | 1 | 7 | 24-27 | 10.1515/fas-2015-0004 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Marcin Kurdelski 1 Andrzej Leski 1 Krzysztof Jankowski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE DEFINITION OF THE LOAD SPECTRUM FOR SU-22 FIGHTER-BOMBER FULL SCALE FATIGUE TEST | The Su-22 fighter-bomber is a military aircraft used in the Polish Air Force since the mid 1980’s. By the decision of the Polish Ministry of Defense the predicted service life for this type of aircraft will be extended to 3200 flight hours. Due to the fact that some aircraft were nearing the end of the service life guaranteed by the manufacturer, the actual service life, determined based on the flight profile in the Polish Air Force, had to be validated. Consequently, the Full Scale Fatigue Test (FSFT) had to be carried out in order to verify that the required service life was attainable. This article describes the process of preparation of the load spectra used in the Su-22 FSFT. Due to the fact that the Su-22 has a variable sweep wing the whole test was divided into three Stages (landing, flight and flap loads) carried out at different wing sweep angles (30°/45°/30°). The spectra were developed using the historical data gathered from Flight Data Recorders (FDR), strain signals acquired during the Operational Load Monitoring program (OLM) and aerodynamic calculations. | Full Scale Fatigue Test, Su-22 fighter-bomber, load spectrum | 2015 | 1 | 7 | 28-33 | 10.1515/fas-2015-0005 | Fatigue of Aircraft Structures |
| Marcin Kurdelski 1 Michał Stefaniuk 1 Wojciech Zieliński 1 Tomasz Bartoszek 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE VERIFICATION OF THE TECHNICAL CONDITIONS OF A COMBAT-TRAINER JET`S AIRFRAME | The combat-trainer jet aircraft is an important element in the process of fighter pilot training. This type of aircraft provides a means of transition from basic training on low-speed propeller trainers to piloting high-speed and highly maneuverable fighter aircraft. Nowadays, in Poland, the PZL TS-11 “ISKRA” jet trainers, designed in 1960s, are employed for training purposes. Because of financial considerations this trainer hasn’t been yet replaced by modern aircraft that conforms to current specifications and needs. As is the case with other aircraft in service of the PLAF, the TS-11 fleet has a large reserve of remaining Hourly Service Life (HSL). This opens an opportunity to extend the Calendar Service Life (CSL), so as it matches the HSL. To this end, a series of technical and research activities needed to be undertaken. The Air Force Institute of Technology is conducting the necessary verification of airframe structural conditions in cooperation with the Military Aviation Works No. 1 J.S.C. (branch in Dęblin) responsible for the overhaul and repair operations. The AFIT’s activities in this program include: • deformation analysis of the selected surface areas of the wing and the fuselage; • assessment of hidden corrosion in riveted joints; • non-destructive testing of selected riveted joints. This paper describes the deformation analysis. As of today, the first stage of the deformation inspection has been completed. At this stage, baseline surface measurements were obtained. Further inspections shall be performed cyclically. The future measurements will be used to establish the areas that deform due to the aircraft operation. | Ageing fleet, Extension of Service Life, deformation analysis | 2015 | 1 | 7 | 34-40 | 10.1515/fas-2015-0006 | Fatigue of Aircraft Structures |
| Michał Dziendzikowski 1 Wojciech Zieliński 1 Łukasz Obrycki 1 Marta Woch 1 Piotr Synaszko 1 Krzysztof Dragan 1 Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | PREDICTIVE MODELS FOR TRANSIENT LOADS OF THE VERTICAL STABILIZER OF AN AIRCRAFT DEVELOPED USING CANONICAN CORRELATION ANALISION | Knowledge about loads occurring in the structure during aircraft operation is vital from the point of view of the damage tolerance approach to aircraft design. In the best-life scenario, such information could be available from a network of sensors, e.g. strain gauges, installed in the aircraft structure to measure local stresses. However, operational loads monitoring (OLM) systems are still not widely applied. Instead, what is available is a set of flight parameters, which by the laws of inertia and aerodynamics help determine the dominant part of loads acting on a given element. This paper discusses the canonical correlation analysis (CCA) as a method for selecting the flight parameters used to predict aircraft loads. CCA allows for the identification of both different modes of stress distribution as well as flight parameters which are best suited for their prediction. The paper presents the application of this method to identify loads acting on the vertical stabilizer of an aircraft. | damage tolerance, loads prediction, loads monitoring | 2015 | 1 | 7 | 41-46 | 10.1515/fas-2015-0007 | Fatigue of Aircraft Structures |
| Piotr Samoraj 1 Michał Sałaciński 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | CONCEPTION OF NEW AIR TARGET SZERSZEŃ-2 | The project to introduce modifications to the air target SZERSZEŃ has been undertaken by the Air Force Institute of Technology. SZERSZEŃ has been used by the Polish Army for 10 years, during which time a number of modifications were introduced. Given this fact, it was decided to develop a new version of this UAV based on the experience gained during its maintenance and operation. Another aspect of this project is to focus on improving the repeatability of production by optimizing the technology processes. To achieve this aim the new instrumentation for the production of composite parts in prepreg technology was designed. The paper reviews the production possibilities for this aircraft using a new technology and presents the advantages of the modified construction and the new technology. | UAV air target, design, technology, integration of control systems | 2015 | 1 | 7 | 47-51 | 10.1515/fas-2015-0008 | Fatigue of Aircraft Structures |
| Bartosz Madejski 1 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | INTERNAL ROUND ROBIN TESTS FOR OPERATORS OF MECHANICAL TESTS | For the characterisation of materials, the aeronautical industry accesses the expertise and the support of independent test laboratories. For the execution of characterisation tests of materials it is important that the test laboratory can fulfil the requirements of the testing expertly and continuously improves knowledge related to the tests. Quality systems are very helpful in this respect. One element of quality management systems is the internal round robin tests. This paper presents a procedure of teaching new operators to carry out tests. In addition, this article underlines how the importance of interlaboratory tests for finding and eliminating mistakes made by new operators. The analysis was performed for tensile tests. This test enables the assessment of operators and significantly improves the quality of tests. | internal round robin tests, tensile tests, quality system, interlaboratory tests | 2015 | 1 | 7 | 52-60 | 10.1515/fas-2015-0009 | Fatigue of Aircraft Structures |
| Jacek Nawrocki1 Kamil Gancarczyk2 Wojciech Manaj3 Robert Albrecht4 Rafał Cygan5 Krzysztof Krupa1 | 1) Research and Development Laboratory for Aerospace Materials, Rzeszow University of Technology, Poland 2) Department of Material Science, Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, Poland 3) Institute of Aviation, Warsaw, Poland 4) Institute of Materials Science, University of Silesia, Katowice, Poland 5) Pratt & Whitney Rzeszów” S.A, factory, Poland | THE EFFECT OF SUPERALLOY STRUCTURE ON ULTRASONIC WAVE PARAMETERS | This paper analyses the nickel based superalloy Inconel 713C casts typically used in high and low pressure turbines of aircraft engines. The ingots were manufactured in the Research and Development Laboratory for Aerospace Materials at the Rzeszów University of Technology. The superalloy structures were analysed by the following methods: X-ray diffraction orientation measurement and ultrasonic wave propagation. Ultrasonic techniques are mainly used to measure the blade wall’s thickness. Measurement accuracy is determined by the velocity of the ultrasonic wave in the material tested. This work evaluates the effect of the nickel-based superalloy microstructure on the velocity of the ultrasonic wave propagation. Three different macrostructures: equiax (EQ), directionally solidified (DS) and single crystal (SX) were analysed. The authors determined the crystal misorientation in the obtained casts as the deviation of [001] crystallographic direction from the withdrawal axis or the main axis of the ingots. The measurements performed allowed researchers to identify significant differences in the wave velocity between EQ, DS and SX structures. | ultrasonic nondestructive testing, superalloy, turbine blade, macrostructure, crystalline orientation | 2015 | 1 | 7 | 61-65 | 10.1515/fas-2015-0010 | Fatigue of Aircraft Structures |
| Wojciech Manaj 1 Wojciech Wronicz 1 Andrzej Michałowski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | PREPARATION OF SAMPLES USED IN FATIGUE TESTING OF AIRCRAFT MATERIALS | The application of a new type of alloy requires the evaluation of its properties, which is typically achieved with destructive methods. For this purpose, among others, static and fatigue mechanical tests are performed. Tests are performed on standardized samples in a way which reflects the level of stress occurring in real elements. These tests should limit random errors associated with sample preparation. For this reason the proper preparation of samples is crucial, not only in terms of their geometric dimensions but also in terms of the residual stress level. A sample preparation process was developed, involving checking samples’ surface for cracks, scratches, roughness, and the state of stress. The measurements are performed with nondestructive methods so as not to affect the proceeding research. In this study, the residual stress and features of a mechanically prepared surface were characterized. The specimens were subjected to various surface finishes mainly, lathe turning and grinding surface conditions. The effects of residual surface stress (measured by XRD) were studied after machining and polishing. | mechanical processing, stress measurement, X-ray diffraction | 2015 | 1 | 7 | 66-68 | 10.1515/fas-2015-0011 | Fatigue of Aircraft Structures |
| Maciej Malicki 1 Bartosz Madejski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | THE IMPACT OF DAMAGE IN INCONEL 718 ON HARDNESS MEASURED BY THE VICKERS METHOD | To prevent failure of machine components it is necessary to measure material damage generated in a component throughout its entire lifetime. Damage can be quantified by means of damage parameters. This paper considers the usefulness of hardness measurements to evaluate damage parameter in Inconel 718. Vickers hardness tests were performed on a specimen with a variable cross section area after tensile testing. The specimen’s geometry enabled the evaluation of damage parameter in respect of hardness measurements made on one individual specimen. | Damage parameter, Vickers hardness, Inconel 718, Tensile test | 2015 | 1 | 7 | 69-79 | 10.1515/fas-2015-0012 | Fatigue of Aircraft Structures |
| Linda K. Kliment 1 Kamran Rokhsaz 1 | 1) Department of Aerospace Engineering, Wichita State University, Wichita, KS 67260-0044, United States of America | COMPARISON OF THE FLIGHT LOADS SPECTRA OF TWO BUSINESS JETS | Operational flight loads have been analyzed from two business jets, a Global 5000 and a Global Express XRS. It is shown that both airframes were subjected to nearly the same number of ground-air-ground cycles, even though the flight times were much different. Flights have been divided into various phases, and loads and turbulence data have been categorized by altitude bands within each phase. Cumulative occurrences of incremental vertical gust load factors have been compared and shown to be comparable for the two airframes. Maneuver load factors have been shown to spread over a wider range of values for the 5000 in every phase. This has been confirmed through comparison of combined loads with those from a CRJ100 and an ERJ-145XR. Derived gust velocities, obtained from the load factors are presented in the form of exceedance spectra. These results from both aircraft are shown to agree well | load spectrum, derived gust velocity, business jet operations | 2014 | 1 | 6 | 5-20 | 10.1515/fas-2014-0001 | Fatigue of Aircraft Structures |
| Aleksander Kural 1 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | WIRELESS ENERGY SUPPLY TO AIRCRAFT STRUCTURAL HEALTH MONITORING NODES USING ULTRASONIC LAMB WAVES | This article is based on research done during the author’s PhD at Cardiff University, UK. A prototype of a novel wireless energy transmission system aimed at the use with wireless aircraft structural health monitoring (SHM) sensor nodes is described. The system uses ultrasonic guided plate waves (Lamb waves) to transmit energy along an aluminium plate, similar to those used in aircraft structures. Three types of piezoelectric transducers generating and receiving the ultrasonic vibration were compared. The Smart Material MFC M8528-P1 was found to achieve the best performance, allowing the transmission of 17 mW across a 54 cm distance, while being driven with a 20 V signal. Laser vibrometer imaging and LISA software simulation of the Lamb wave propagation in the experimental plate were also performed. Based on these, ideas for a further development of the system were proposed. | Structural Health Monitoring, wireless ultrasonic energy transmission system, transmission transducers tests | 2014 | 1 | 6 | 21-28 | 10.1515/fas-2014-0002 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska1 Andrzej Baczmański2 Kamil Sołoducha2 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) AGH-University of Science and Technology, WFIS, Al. Mickiewicza 30, 30-059 Kraków, Poland | SYNCHROTRON RADIATION APPLICATION FOR LATTICE STRAIN MEASUREMENTS | The methods most commonly used for the determination of the elastic lattice deformation and distortion are diffraction methods, which enable to perform measurements of stresses and elastic properties of polycrystalline materials. The main advantages of diffraction methods are associated with their non-destructive character and the possibility to be used for macrostress and microstress analysis of multiphase and anisotropic materials. Diffraction methods enable taking measurements selectively only for a chosen alloy phase. This is very convenient when several phases are present in the sample since measurements of separate diffraction peaks allow the behaviour of each phase to be investigated independently. In this work, a method for analysis of diffraction with synchrotron radiation is described. The methodology is based on the measurements of lattice strains during “in situ” tensile testing for several hkl reflections and for different orientations of the sample with respect to the scattering vector. Some initial results are presented. | diffraction, synchrotron radiation, lattice strain, micromechanical properties of duplex steel, in situ tensile test | 2014 | 1 | 6 | 29-38 | 10.1515/fas-2014-0003 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | COMPARISON OF SELECTED RIVET AND RIVETING INSTRUCTIONS | Sheet metal parts are widely used in airframes. Most sheet metal parts used in aircraft assembly are joined using rivets. A number of riveting parameters directly influence fatigue properties of a structure. These include a rivet length, driven head diameter, tolerance of a rivet hole and a rivet shank diameter, and a protective layer among others. Unfavourable selection or change of these parameters can lead to stress concentrations and early crack nucleation. Crack growth can cause failure of a whole structure. The selection of the riveting process parameters is usually described in a company’s internal instruction (process specifications). Some parameters can be defined in an aircraft's technical specifications. Riveting instructions among other production documentation are part of a company's closely guarded know-how. The author obtained access to two riveting instructions used in Poland and three such documents used in western Europe. The author was permitted to publish the comparison of the parameters from these documents but he is not supposed to reveal any other information. For the reasons stated above, the following cryptonyms were used in the article: Poland-1, Poland-2, West-1, West-2 and West-3. The quality of a joint also depends on rivets parameters that are defined in rivets standards. For this reason, selected rivets defined in the Polish and Russian industry standards as well as western standards are compared in this paper. Tolerances of a rivet and a hole diameter, clearances between a rivet and a hole, rivet lengths anticipated for driven head formation as well as driven head dimensions are taken into account. | Riveted joints, rivets, riveting parameters, riveting instructions and standards | 2014 | 1 | 6 | 39-62 | 10.1515/fas-2014-0004 | Fatigue of Aircraft Structures |
| Wojciech Wronicz 1 Jerzy Kaniowski 1 | 1) Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland | THE ANALYSIS OF THE INFLUENCE OF RIVETING PARAMETERS SPECIFIED IN SELECTED RIVETING INSTRUCTIONS ON RESIDUAL STRESSES | The riveting parameters strongly affect residual stresses induced during riveting, which in turn have an impact on the fatigue life of riveted joints. Since rivets are established as critical from the fatigue point of view, the fatigue life of riveted joints often determines the life of the whole structure. The authors were able to become acquainted with three riveting instructions (process specifications) used by the aerospace companies from western Europe. This work presents the analysis of the riveting parameters' influence on residual stresses around the rivets. The impact of the clearance between a rivet shank and a hole as well as driven head dimensions and a rivet length were investigated based on the numerical simulations. The aim of the analysis was to determine the range of stresses variation when the requirements of the riveting instructions are fulfilled. For the purposes of comparison, the calculations were performed also with the parameters as specified in the Polish industry standards. For all calculations, the geometry of the universal rivet MS20470 was used. The results show that residual stresses can vary strongly depending on the parameters in the instructions and standard requirements. | Riveting, residual stress, FEA, simulation | 2014 | 1 | 6 | 63-71 | 10.1515/fas-2014-0005 | Fatigue of Aircraft Structures |
| Janusz Lisiecki 1 Dominik Nowakowski 1 Piotr Reymer 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | FATIGUE PROPERTIES OF POLYURETHANE FOAMS, WITH SPECIAL EMPHASIS ON AUXETIC FOAMS, USED FOR HELICOPTER PILOT SEAT CUSHION INSERTS | Seat cushion inserts in military helicopters crew seats, as suggested by the helicopters manufacturers, are made of traditional polyurethane foams. Elastic polyurethane auxetic foams are materials that exhibit different utility properties compared to traditionally used polyurethane foams, such as polyether or polystyrene foams. All the differences result from the primary physical property of elastic polyurethane auxetic foams which is a negative Poisson’s ratio. Auxetic materials are characterized by better utility properties than conventional foam materials – they can potentially increase safety in the event of a crash and offer higher comfort during regular use. Application of auxetic materials as seat cushion inserts would also decrease harmful health effects of vibrations. This paper presents the results of the fatigue tests carried out on different foam samples by pressing an indenter into the foams' surface that was much larger than the indenter’s surface. A maximum value of the load used during the test was within a defined range in every fatigue cycle. In order to test 150x150x50 mm foam samples a special indenter was designed and manufactured according to the PN-EN ISO 3385 and PN-EN ISO 2439 standards. The indenter’s dimensions were consistent with the standards in relation to the tested foams' size. The fatigue tests of both conventional and auxetic foams were carried out according to the above given standards by applying 80,000 load cycles at 70 cycle/min frequency. Tests of viscoelastic foam and multilayer foam specimens, for which the upper layer was made of viscoelastic foam, were carried out according to the ASTM D 3574 standard applying 12 ,000 load cycles at 10 cycle/min frequency. All the tests were carried out using the MTS 370.10 strength testing machine. Changes in thickness and density were determined throughout the tests. Moreover, the influence of the volumetric compression ratio on the fatigue properties of auxetic foam samples and the dependence of foam deflection on the number of cycles were examined. Finally, the test results obtained for conventional and auxetic foams were compared and discussed. | cellular plastics, fatigue properties investigations, helicopter pilot seats | 2014 | 1 | 6 | 72-78 | 10.1515/fas-2014-0006 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Andrzej Leski 1 Wojciech Zieliński 1 Krzysztof Jankowski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE CONCEPT OF A FULL SCALE FATIGUE TEST OF A SU-22 FIGHTER BOMBER | This article presents a concept of the full scale fatigue test of a Su-22 fighter bomber. The authors define the general concept and goals of the test as well as the tasks to be accomplished in the preparation stage. The current work status is summarized and future tasks are defined. | full scale fatigue test, Su-22 fighter bomber, life extension program | 2014 | 1 | 6 | 79-87 | 10.1515/fas-2014-0007 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 Henryk Gruszecki 1 Leszek Pieróg 1 Janusz Pietruszka 1 | 1) Polskie Zakłady Lotnicze Sp. z o.o., ul. Wojska Polskiego 3, 39-300 Mielec, Poland | SELECTED ASPECTS RELATED TO PREPARATION OF A FATIGUE TEST PLAN OF A METALLIC AIRFRAME | Service life of the PZL M28 is computed based on the results of the full-scale fatigue tests of the structure [1]. As the PZL M28 is a commuter category airplane according to the 14 CFR Part 23 and CS-23 regulations, the test objects were: (1) wing and wing load carry-through structure, (2) empennage and attached fuselage structure. Additionally, there were fatigue tests carried out for the landing gear and other selected elements including control system elements. The aircraft load carry-through structure is metallic and the cabin is unpressurized. The fatigue tests were conducted stage-by-stage. As tests progressed, it was possible to extend the aircraft target service life, applying the safe-life philosophy with reference to the primary components of the load carrythrough structure. The article brings into attention selected issues related to the fatigue tests plan preparation, with focus on wing and wing load carry-through structure test. | metallic airframe structure, full scale fatigue tests | 2014 | 1 | 6 | 88-94 | 10.1515/fas-2014-0008 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 Jerzy Chodur 1 Janusz Pietruszka 1 | 1) Polskie Zakłady Lotnicze Sp. z o.o., ul. Wojska Polskiego 3, 39-300 Mielec, Poland | SELECTED ASPECTS RELATED TO PREPARATION OF FATIGUE TESTS OF A METALLIC AIRFRAME | The basis for the computation of the service life of the PZL M28 was the results of the full-scale fatigue tests of the structure [1]. As the PZL M28 is a commuter category airplane according to the 14 CFR Part 23 and CS-23 regulations, the test objects were: (1) wing and wing load carrythrough structure, (2) empennage and attached fuselage structure. Additionally, there were fatigue tests carried out for the landing gear and other selected elements including control system elements. The aircraft load carry-through structure is metallic and the cabin is unpressurized. The fatigue tests were conducted stage-by-stage. As the tests progressed, it was possible to extend the aircraft’s target service life, applying a safe life philosophy with reference to the primary components of the load carry-through structure. This paper brings into attention selected issues related to the fatigue tests preparation (the stage following the preparation of the test plan), with focus on the wing and wing load carrythrough structure. | metallic airframe structure, full scale fatigue tests | 2014 | 1 | 6 | 95-101 | 10.1515/fas-2014-0009 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 Jerzy Chodur 1 Janusz Pietruszka 1 | 1) Polskie Zakłady Lotnicze Sp. z o.o., ul. Wojska Polskiego 3, 39-300 Mielec, Poland | SELECTED ASPECTS RELATED TO THE APPLIED LOADS CONTROL DURING FATIGUE TESTS OF A METALLIC AIRFRAME | Service life of the PZL M28 is computed based on the results of the full-scale fatigue tests of the structure [1]. As the PZL M28 is a commuter category airplane according to the 14 CFR Part 23 and CS-23 regulations, the test objects are: (1) wing and wing load carry-through structure, (2) empennage and attached fuselage structure. Additionally, there are fatigue tests carried out for the landing gear and other selected elements including control system elements. The aircraft load carry-through structure is metallic and the cabin is unpressurized. The fatigue tests are conducted stage-by-stage. As tests progress, it is possible to extend the aircraft target service life, applying the safe life philosophy with reference to the primary components of the load carry-through structure. | metallic airframe structure, full scale fatigue tests | 2014 | 1 | 6 | 102-106 | 10.1515/fas-2014-0010 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 Henryk Gruszecki 1 Leszek Pieróg 1 Franciszek Deszcz 1 Janusz Pietruszka 1 | 1) Polskie Zakłady Lotnicze Sp. z o.o., ul. Wojska Polskiego 3, 39-300 Mielec, Poland | STRESS ANALYSIS OF THE PZL M28’S AIRFRAME SUBJECTED TO REPAIRS DURING FATIGUE TESTS | The PZL M28’s service life is determined based on the fatigue tests of the wing and wing loadscarrythrough structure. During the fatigue test, the first occurrence of significance was the appearance of a in the area of the wing where loads are applied from the strut. It was demonstrated during further activities that repairs of the wing and other basic assemblies enabled, when performed at an appropriate time, the airplane’s service life to be significantly increase. In the case of each design change implemented in the airframe subject to the fatigue testing, a stress analysis of the airframe was required in order to check if local changes, i.e. local repairs, did not affect the stress level in other tested areas. This helped to avoid significant stress redistribution in the airframe after the repair, so the fatigue test was still valid for all areas of interest. | metallic airframe structure, full scale fatigue tests | 2014 | 1 | 6 | 107-112 | 10.1515/fas-2014-0011 | Fatigue of Aircraft Structures |
| Michał Dziendzikowski1 Krzysztof Dragan1 Artur Kurnyta1 Łukasz Kornas1 Adam Latoszek1 Magdalena Zabłocka1 Sylwester Kłysz1,2 Andrzej Leski1 Marek Chalimoniuk1 Janusz Giewoń1 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury, ul. Oczapowskiego 2, 10-719 Olsztyn, Poland | AN APPROACH TO STRUCTURAL HEALTH MONITORING OF COMPOSITE STRUCTURES BASED ON EMBEDDED PZT TRANSDUCERS | One approach to developing a system of continues automated monitoring of structural health is to use elastic waves excited in a given medium by a piezoelectric transducers network. Depending on their source and the geometry of the structure under consideration elastic waves can propagate over a significant distance. They are also sensitive to local structure discontinuities and deformations providing a tool for detecting local damage in large aerospace structures. This paper investigates the issue of Barely Visible Impact Damages (BVIDs) detection in composite materials. The model description and the results of impact tests verifying damage detection capabilities of the proposed signal characteristics are presented in the paper. | structural health monitoring, PZT sensor network, barely visible impact damages | 2014 | 1 | 6 | 113-118 | 10.1515/fas-2014-0012 | Fatigue of Aircraft Structures |
| Krzysztof Jankowski 1 Piotr Reymer 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | SIMULATING CRACK PROPAGATION OF A SELECTED STRUCTURAL COMPONENT OF THE PZL-130 ORLIK TC-II AIRCRAFTS | This paper presents the process of estimating crack propagation within a selected structural component of the PZL-130 Orlik TC-II using a numerical model. The model is based on technical drawings and measurements of the real structure. The proper definition of the geometry, including the location and size of the gap between elements, is significant for mesh generation. During the simulation process the gap is combined node by node. Each time, the strain energy release rate (G) is calculated. The stress intensity factor and geometry correction factor are defined for consecutive crack lengths, and used further on to estimate crack propagation. | structural integrity, crack propagation simulation, geometry correction factor | 2014 | 1 | 6 | 119-127 | 10.1515/fas-2014-0013 | Fatigue of Aircraft Structures |
| Krzysztof Dragan1 Michał Dziendzikowski1 Artur Kurnyta1 Adam Latoszek1 Andrzej Leski1 Sylwester Kłysz1,2 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury, ul. Oczapowskiego 2, 10-719 Olsztyn, Poland | AN ON-LINE MULTIWAY APPROACH TO IN-SITU NDI LOOKING AT THE PZL-130TCII | Providing a reliable and universal Structural Health Monitoring (SHM) system allowing for remote aircraft inspections and a reduction of maintenance costs is a major challenge confronting the aerospace industry today. SHM based on guided Lamb waves is one of the approaches capable of addressing the issue while satisfying all the associated requirements. This paper presents a holistic approach to the continuous real time damage growth monitoring and early damage detection in aircraft structure. The main component of the system is a piezoelectric transducers (PZT) network. It is complemented by other SHM methods: Comparative Vacuum Monitoring (CVMTM) and Resistance Gauges at selected aircraft hot spots. The paper offers the description of damage detection capabilities including the analysis of data collected from the PZL-130 Orlik aircraft full-scale fatigue test. | Structural Health Monitoring, PZT Sensor Network, Fatigue Crack Detection, Full Scale Fatigue Test | 2013 | 1 | 5 | 5-11 | 10.2478/fas-2013-0001 | Fatigue of Aircraft Structures |
| Katarína Draganová 1 Josef Blažek 1 Dušan Praslička 1 František Kmec 1 | 1) Department of Aviation Technical Studies, Faculty of Aeronautics, Technical University of Kosice, Rampova 7, 041 21 Kosice, Slovakia | POSSIBILE APPLICATIONS OF MAGNETIC MICROWIRES IN AVIATION | Magnetic microwires have been rediscovered due to a number of the unusual magnetic properties and their potential applications. The paper concerns glass-coated magnetic microwires composed of a ferromagnetic metallic core with a diameter of 0.6 – 30 μm and of a glass coat with a thickness of 2 – 20 μm. The fabrication process and magnetic properties of these microwires are described. Due to their unique properties microwires can be used as a sensing element of sensors. Microwire-based sensors can be used in a wide range of aviation applications as magnetic field sensors, tensile stress sensors or temperature sensors. The main advantages of microwire-based sensors are associated with their small dimensions and weight, which play a very important role in aviation. | Aviation, Magnetic microwires sensors, Magnetic field sensors, Mechanical stress sensors, temperature sensors | 2013 | 1 | 5 | 12-17 | 10.2478/fas-2013-0002 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska1 Andrzej Baczmański2 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) AGH-University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Kraków, Poland | MICROMECHANICAL PROPERTIES AND STRESS MEASUREMENTS WITH DIFFRACTION METHODS | Diffraction methods are commonly used for the determination of the elastic lattice deformation and distortion from the displacement and broadening of the diffraction peak. These methods enable researchers to measure stresses and elastic properties of polycrystalline materials. The main advantages of diffraction methods are their non-destructive character and the possibility of macrostress and microstress analysis for multiphase and anisotropic materials. Measurements are performed selectively only for crystallites contributing to the measured diffraction peak, i.e. for the grains having lattice orientations for which the Bragg condition is satisfied. When several phases are present in the sample, measurements of separate diffraction peaks allow for the behaviour of each phase to be investigated independently. This method can be applied without any limitations to flat specimens. Numerical calculations of residual stresses around the rivets imply a very high stress gradientin the case of tangential stresses as well in the case of radial stresses. Attempting to verify these predictions, the residual stress measurements with an X-ray diffractometer were performed on riveted samples after the riveting process. In addition, complementary measurements of strain values with strain gauges during the riveting process were performed as well as the finite elements modelling. The aim of these measurements was to determine the stress values around the rivets and to compare results obtained with different techniques. On the other hand, the multi-scale crystallographic model of elastoplastic deformation is very convenient for the study of elastoplastic properties in microscopic and macroscopic scales. Comparison of experimental data with model predictions allows us to understand the physical phenomena that occur during a sample's deformation at the level of polycrystalline grains. Moreover, the micro and macro parameters of elastoplastic deformation can be experimentally established. It should be stated that the characterisation of the residual stress field and elastic properties is important in the study of the mechanical behaviour of polycrystalline materials, including plasticity and damage phenomena. In this work, a new analysis method of neutron diffraction results obtained during in-situ tensile load is proposed and tested. The methodology is based on the measurements of lattice strains during in-situ tensile testing for several hkl reflections and for different orientations of the sample with respect to the scattering vector. As the result, the full stress tensor for preferred texture orientations in function of the applied stress can be determined using the crystallite group method. The experimental data are presented and compared with the self-consistent model calculations performed for groups of grains selected by different hkl reflections. | X-ray diffraction, stress measurements on riveted samples, duplex steel, composites, stress measurements during in-situ tensile test, stress concentarion tensor, necking phenomenon | 2013 | 1 | 5 | 18-39 | 10.2478/fas-2013-0003 | Fatigue of Aircraft Structures |
| Mirosław Rodzewicz 1 Dominik Głowacki 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | INVESTIGATIONS INTO LOAD SPECTRA OF UAVS AIRCRAFT | The paper contains a description of a novel approach to the load spectra estimation applied to UAVs. The authors have developed a number of tools in the LabVIEW environment enabling an in-depth analysis of flight-log data. One major achievement was the separation of the load spectra induced by steering and the load spectra induced by turbulence. The authors have shown a significant influence of both of the main load sources on the fatigue life of the UAV airframe, calculated based on the P-M hypothesis. This approach to fatigue testing of composite UAV airframes needs to take into account the rate of load variations as these may affect the fatigue life of tested structures. The paper presents several schemes of calculation algorithms and a number of well-illustrated examples of the tests and investigations results. | UAV loads, load spectrum, manual control, autopilot | 2013 | 1 | 5 | 40-52 | 10.2478/fas-2013-0004 | Fatigue of Aircraft Structures |
| Artur Kurnyta 1 Krzysztof Dragan 1 Michał Dziendzikowski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | ASSESSMENT OF SENSOR TECHNOLOGIES FOR AIRCRAFT SHM SYSTEMS | SHM is a monitoring system which uses sensors, actuators and data transmission, acquisition and analysis, permanently integrated with the inspected object. The objective of SHM is to detect, localize, identify and predict development of fatigue fractures, increasing safety and reliability. This paper presents an assessment of sensor technologies used in aircraft SHM system. Due to the fact that most of these measurement methods are relatively new and still under development the present appraisal focuses on a number of parameters with reference to each method, including a sensor’s installation issues, reliability, power consumption, sensor infrastructure, sensitivity and cost and availability. The work is predominantly focused on the assessment of permanently bonded sensors, such as foil strain gages, Comparative Vacuum Monitoring (CVM), Piezo sensors (PZT), Eddy-Current Transducers (ECT). Finally, all these methods are briefly discussed. | SHM, sensor, fatigue crack, crack detection methods, usage monitoring | 2013 | 1 | 5 | 53-59 | 10.2478/fas-2013-0005 | Fatigue of Aircraft Structures |
| Miroslav Šmelko 1 Dušan Praslička 1 Josef Blažek 1 | 1) Technical University of Kosice, Faculty of Aeronautics, Rampova 7, 041 21 Kosice, Slovakia | ADVANCED MAGNETIC MATERIALS FOR AERONAUTICS | In the field of magnetic sensors, magnetic microwires with positive magnetostriction are the materials of the future. Their mechanical and magnetic properties render them ideal materials for applications in aeronautics. A single microwire with a 40 μm diameter and a length of 10 mm is capable of capturing information about tensile stresses, magnetic fields, temperature and distance. This information is carried by a parameter called the Switching Field, HSW, which is specific for different types of microwire. Numerous physical qualities affect the HSW and through sensing of HSW, these qualities may be quantified. (A number of physical qualities affecting HSW can be sensed and quantified by means of a contactless induction method.) What distinguishes the system developed by the present authors from other measuring systems based on magnetic microwires is the positioning of a microwire outside the coil system. Thanks to this improvement it is possible to use microwires embedded directly in the construction material. Small dimensions microwires do not damage the structure of the construction material. The absence of a galvanic connection makes this technology even more interesting compared with traditional forge gauges. Offering the possibility of the simultaneous measuring of four parameters, this technology can be used in a wide range of aviation applications. Measurements of an external magnetic field can be used for the navigation and stabilization of an aerial vehicle. Tensile stress and distance measuring can be helpful to understand some processes occurring under the surface of the construction material and also to perform fatigue monitoring or structure load monitoring. Another big advantage of magnetic microwires is the low price. Just 1 gram of base material is sufficient to prepare about 40 km of microwire. All these features combine to offer us a material ideal for Smart Sensors, possibly available for use in the near future. | Microwires, Strain Gauge, Mechanical Stress, Contactless | 2013 | 1 | 5 | 60-65 | 10.2478/fas-2013-0006 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | LOCAL PHENOMENA DURING RIVETING PROCESS | The paper presents experimental and numerical study of the local phenomena during the riveting process. It is commonly accepted that technological factors of the riveting process has a strong influence on the fatigue life of riveted joints. The authors analysed the papers concerned the experimental researches of the riveting force influence on fatigue life. The magnitude of the life increase caused by the riveting force increase suggests the authors that this is not only the result of beneficial stress system but the change of the joint formation mechanism has taken place. This was an inspiration to undertake more detailed researches of the riveting process. The strain progress during the riveting process has been experimentally investigated for four types of aluminium rivets used in airframes. Measurements confirm very high strains near the driven head. For some types of rivets the reversal strain signal has been recorded. Several FE model has been use to investigate the riveting process. The axisymmetric and solid models were used. The agreement of experimental and numerical results in some cases were good, in other cases the numerical models demand further development. In any calculations, the reversal strain effect has not been obtained, This suggest that it is result of the phenomenon which has not been taken into account in numerical modelling. The working hypothesis has been assumed that during the riveting process adhesive joints (called cold welding) were formed and destroyed during the process, what was the reason of the observed reversal strain signal. The authors are going to continue this investigation. | Riveting, fatigue, strain gauge, FE, residual stress, airframes | 2013 | 1 | 5 | 66-78 | 10.2478/fas-2013-0007 | Fatigue of Aircraft Structures |
| Krzysztof Dragan1 Łukasz Kornas1 Michał Kosmatka1 Andrzej Leski1 Michał Sałaciński1 Piotr Synaszko1 Jarosław Bieniaś2 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland 2) Lublin University of Technology, Nadbystrzycka 38D street, 20-618 Lublin, Poland | DAMAGE DETECTION AND SIZE QUANTIFICATION OF FML WITH THE USE OF NDE | Composite materials have been developed in recent years. A new generation of structural composite materials for advanced aircraft is Fibre Metal Laminates (FML). They are hybrid composites consisting of alternating thin layers of metal sheets and fiber-reinforced composite material. FMLs have both low weight and good mechanical properties (high damage tolerance: fatigue and impact characteristics, corrosion and fire resistance). Quality control of materials and structures in aircraft is an important issue, also for Fibre Metal Laminates. For FML parts, a 100% non-destructive inspection for internal quality during the manufacturing process is required. In the case of FML composites, the most relevant defects that should be detected by non-destructive testing are porosity and delaminations. In this paper, a number of different non-destructive methods for the inspection of Fibre Metal Laminates were studied. The possibility of quality control of manufactured FML laminates detection of defects as well as the procedures and processes are presented and discussed. | fibre metal laminates, composites, non-destructive testing | 2012 | 1 | 4 | 5-9 | 10.2478/v10164-012-0051-8 | Fatigue of Aircraft Structures |
| Krzysztof Dragan1,2 Michał Dziendzikowski1 Andrzej Leski1 Ziemowit Dworakowski1 Tadeusz Uhl2 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland 2) AGH-University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Kraków, Poland | AN APPROACH TO DAMAGE DETECTION IN THE AIRCRAFT STRUCTURE WITH THE USE OF INTEGRATED SENSORS – THE SYMOST PROJECT | This paper presents an approach to damage growth monitoring and early damage detection in the structure of PZL – 130 ORLIK TC II turbo-prop military trainer aft using the statistical models elaborated by the Polish Air Force Institute of Technology (AFIT) and the network of the sensors attached to the structure. Drawing on the previous experiences of the AFIT and AGH in structural health monitoring, the present research will deploy an array of the PZT sensors in the structure of the PZL -130 Orlik TC II aircraft. The aircraft has just started Full Scale Fatigue Test (FSFT) that will continue up to 2013. The FSFT of the structure is necessary as a consequence of the structure modification and the change of the maintenance system - the transition to Condition Based Maintenance. In this paper, a novel approach to the monitoring of the aircraft hot-spots will be presented. Special attention will be paid to the preliminary results of the statistical models that provide an automated tool to infer about the presence of damage and its size. In particular, the effectiveness of the selected signal characteristics will be assessed using dimensional reduction methods (PCA) and the so-called averaged damage indices will be delivered. Moreover, the results of the signal classification based on the neural network will be presented alongside the numerical model of the wave propagation. The work contains selected information about the project scope and the results achieved at the preliminary stage of the project. | averaged damage index, Full Scale Fatigue Test, damage growth monitoring | 2012 | 1 | 4 | 10-16 | 10.2478/v10164-012-0052-7 | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 Jerzy Kaniowski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | X-RAY DIFFRACTION MEASUREMENTS FOR RIVETED JOINTS. THE APPLICATION OF A NOVEL METHODOLOGY | The X-ray diffraction method is the best, widely available, non-destructive measurement method used to determine the residual and load stresses in crystalline materials. This method can be applied without any limitations to flat specimens. Depending on the equipment geometry, the type of material and geometry of the specimen, there are many limitations, restrictions and recommendations which have to be fulfilled to obtain reliable results. This was the reason for working out a methodology for X-ray diffraction stress measurements for riveted specimens. The first case to analyze is the necessity of choosing an X-ray tube suitable for the specimen material which will give the diffraction peaks in the range of 2Θ angles between 120° and 180°. Afterwards it is crucial to make the best selection of Bragg’s angle 2Θ. In the vast majority of cases the best selection is the possibly biggest 2Θ angle because of the best accuracy of the measurement. However, for example for aluminum alloys (for K Cr radiation), this choice is not so obvious. It is much more convenient to perform measurements not for the highest diffraction angle. The best selection in this case is 2Θ=139,3°, and not 156,7°. Other selections which are necessary to be made before measurements are the collimator diameter, time of exposure, tilts and φ oscillations. The proper selection of these parameters is crucial for the fast and efficient performing of measurements and for obtaining reliable results. Before performing the measurement, especially in the case of the specimen with complicated geometry (for example in the case of riveted specimens made of aluminum alloys), it is necessary to analyze the results obtained paying special attention to the possibility of the appearing of the rivet head/driven rivet head shadow during the measurement. The work describes differences between the X-ray stress measurement results obtained without any interference and the results received after eliminating the selected diffraction peaks for which the shadow of rivet head/driven rivet head has appeared. | brak | 2012 | 1 | 4 | 17-28 | 10.2478/v10164-012-0053-6 | Fatigue of Aircraft Structures |
| Andrzej Leski1 Sylwester Kłysz1,2 Janusz Lisiecki1 Gabriel Gmurczyk1 Piotr Reymer1 Dariusz Bochenek1 Dariusz Zasada3 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury, ul. Oczapowskiego 2, 10-719 Olsztyn, Poland 3) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | INTRODUCTION OF FATIGUE MARKERS IN FULL SCALE FATIGUE TEST OF AN AIRCRAFT STRUCTURE | Air Force Institute of Technology participates in the service life assessment programme SEWST. The aim of this programme, funded by the Polish Ministry of Defense, is to modify the operation system of PZL-130 "Orlik" TC-II turbo propelled trainer aircraft. The structural part of the programme is focused on the Full Scale Fatigue Test of the whole airframe to be conducted at the VZLU in the Czech Republic. The load spectrum for the test was developed by the AFIT based on the flight test results. The basic load block represents 200 simulated flight hours and consists of 194 flights showing different levels of severity. At the end of the Full Scale Fatigue Test a teardown inspection is planned during which it would be most beneficial to be able to determine crack propagation rate by means of a crack surface inspection. Markers are usually visible on most fatigue crack surfaces, however they occur randomly therefore it is almost impossible to conclude anything about the crack history. Since the preliminary load block consisted of separate flights (flight loads together with landing and taxing loads) showing significantly different levels of severity, the easiest way to modify the load block was to change the order of flights within the block. Hence a pilot programme was started at the AFIT which was focused on the determination of the influence of flight sequence on crack appearance. Several load blocks were determined using various techniques of rearranging the order of flights within the preliminary load spectrum. This approach ensured the preservation of the initial severity of the load block and simultaneously enabled a significant increase in the probability of the markers occurrence introducing neither artificial underloads nor overloads that would most probably affect the crack propagation rate. Fatigue crack surfaces were inspected using Scanning Electron Microscope. As a result of the investigations a series of images were obtained showing the specimen microstructure with visible markers arranged in the desired sequences. Based on the obtained pictures the most promising load block arrangements were chosen for the Full Scale Fatigue Test. | Full Scale Fatigue Test, fatigue markers, load block rearrangement | 2012 | 1 | 4 | 29-37 | 10.2478/v10164-012-0054-5 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | THE SYNTHETIC DESCRIPTION OF THE RESULTS, SCIENTIFIC ACHIEVEMENTS AND PRACTICAL APPLICATIONS OF THE EUREKA − IMPERJA PROJECT, E3496! − “IMPROVING THE FATIGUE PERFORMANCE OF RIVETED JOINTS IN AIRFRAMES” | The goal of the project was to increase the fatigue life of the riveted joints in order to achieve an increase in the aircraft service life, a smaller number of inspections and, consequently, lower aircraft operating costs. This goal was achieved by the analysis and optimization of the riveting process as well as by improving the fatigue life prediction methods (crack initiation and propagation). The project outcomes enable a more precise fatigue life estimation and an increase in Time Before Overhaul (TBO) for currently used aircraft, as well as optimize the design of new aircraft from the fatigue point of view. All activities in the aerospace area are subjected to regulations. Significant formal changes have taken place in the aircraft design regulations in recent years. The European Aviation Safety Agency, established in the EU in 2002, introduced the Certification Specification (CS), which contains the airworthiness code and acceptable means of compliance for particular types of an aircraft. In 1997, in the US, the Code of Federal Regulations (CFR) was introduced relating to all areas of life including politics, law and economy. The Title 14 CFR contains aircraft design regulations. Other changes included the introduction of the damage tolerance as a basic methodology for commuter aircraft. The standards recommended by the Certification Specification and the Title 14 CFR are the American Society for Testing and Materials (ASTM) Standards for Material Tests and the NASM1312 Standard Practice Fastener Test Method Standards for Riveted Joint Tests. | brak | 2012 | 1 | 4 | 38-57 | 10.2478/v10164-012-0055-4 | Fatigue of Aircraft Structures |
| Artur Kurnyta 1 Piotr Reymer 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | PRELIMINARY VERIFICATION OF SELECTED SOLUTIONS FOR CRACK DETECTION | Throughout its service life an aircraft is subjected to varying loads. Because of those periodically appearing stresses, undesirable and irreversible changes in structure may occur. As a consequence, cracks are formed, which reduce aircraft structural strength, significantly affecting structural integrity. For that reason, intensive research works are carried out around the world to develop innovative and reliable methods for detection of cracks initiation and propagation. This paper presents two methods of crack detection. One of them uses wireless polymer gages for determining deformation in a test region. The other one uses electrical, resistive ladder sensors for detection of cracks and their length determination. | Fatigue crack, crack detection, DMI SR2, polymer gage, ladder sensor | 2012 | 1 | 4 | 58-63 | 10.2478/v10164-012-0056-3 | Fatigue of Aircraft Structures |
| Adam Lipski 1 | 1) Bydgoszcz University of Technology, Faculty of Mechanical Engineering, al. prof. S. Kaliskiego 7, 85-796 Bydgoszcz, Poland | THE INFLUENCE OF THE DEGREE OF THE RIVET HOLE SIZING ON THE FATIGUE LIFE | The paper presents the results of fatigue tests of specimens with sized rivet holes. Samples for tests were made of 0.05” (1.27 mm) thick non-clad plates of aluminium grade 2024-T3. Rivet holes were prepared assuming that they shall be used for 3 mm nominal diameter snap head rivets for aviation-related purposes. Different sizing degrees were achieved by drilling holes of different diameters in the samples followed by the sizing process using a sizing mandrel of the same diameter of 3.15 mm. Holes in the test samples were drilled using special device ensuring appropriate quality and repeatability of the holes. Five different sizing degrees were achieved be means of five drills of different diameters. Samples with holes of varying degrees of sizing were tested under constant amplitude sinusoidal loading conditions (cycle asymmetry coefficient R = 0) at the load frequency of 5 Hz. The study was conducted at three levels of maximum stress in the cycle. Fatigue life test results were presented in the form of fatigue diagrams (regression lines) determined in the bi-logarithmic coordinate system log N, log Smax. The results of the fatigue life tests received for the drilled as well as drilled and reamed holes were also presentedfor comparison. The results obtained lead to the conclusion that that the lowest fatigue life characterises samples with drilled holes and drilled and reamed holes. Fatigue life of specimens with holes for rivets improved (by 50% to 74%, depending on load level), even as a result of the hole surface polishing only (minimum sizing degree), whilst the two-fold growth of fatigue life was achieved for holes of a slight sizing degree. A further significant increase in fatigue life was achieved by the cold work of the hole's surface. Based on the location of the fatigue diagrams and the fatigue life tests results, it may be concluded that the higher a sizing degree, the higher the fatigue life growth. The growth is also proportional to the specimen load level: the lower the load level, the higher the fatigue life growth. Fatigue diagrams obtained from tests were divided into three groups: diagrams for drilled holes and drilled and reamed holes, diagrams for holes with a low degree of sizing and diagrams for holes with a high degree of sizing. This division was confirmed by statistical tests of regression lines parallelism by the “peer-to-peer” method. | brak | 2012 | 1 | 4 | 64-69 | 10.2478/v10164-012-0057-2 | Fatigue of Aircraft Structures |
| Józef Brzęczek 1 Henryk Gruszecki 1 Leszek Pieróg 1 Janusz Pietruszka 1 | 1) Polskie Zakłady Lotnicze Sp. z o.o., ul. Wojska Polskiego 3, 39-300 Mielec, Poland | FULL SCALE FATIGUE TEST OF NEW UNDERCARRIAGE FOR COMMUTER AIRCRAFT | Fatigue testing of the new main landing gear for the PZL M28 aircraft was conducted in Polskie Zakłady Lotnicze Sp. z o.o. in Mielec using MTS Aero 90-LT system. The test was conducted in a flight-by-flight manner with loads resulting from landing, taxiing, maneuvering and braking. The undercarriage structure is made of high tensile strength low alloy steel. FEM analyses were performed before the tests in order to find critical points and to obtain information about loads which may be neglected. During the test fatigue damage was observed, which led to splitting the test into two separate tests performed in independent rigs: the test of the undercarriage leg and the test of the shock absorber. | brak | 2012 | 1 | 4 | 70-75 | 10.2478/v10164-012-0058-1 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Andrzej Leski 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | RECENT PROGRESS IN FULL SCALE FATIGUE TEST OF PZL-130 "ORLIK" TC-II STRUCTURE | This article presents preparation of the Full Scale Fatigue Test of the PZL-130 "Orlik" TC-II. After completing the flight load acquisition stage [1] a load block representing 200 Simulated Flight Hours in 194 flights was developed. This load block was further modified in order to introduce fatigue markers on the crack surface [2] visible during Quantitative Fractography, planned to take place during the Teardown Inspection of the structure after completion of the test. Meanwhile, the test rig along with the loading system and the test specimen were prepared at Výzkumný a Zkušební Letecký Ústav (VZLU, Prague, Czech Republic). The test specimen, consisting of the overhauled fuselage, modernized wings and the landing gear, was instrumented with the identical strain gauge measuring system as presented in [3], which was calibrated before the commencement of fatigue testing. Finally, some preliminary issues encountered during the fatigue test startup were highlighted and the outline for future work was described. | Full Scale Fatigue Test, Non Destructive Inspection, Teardown Inspection, Quantitative Fractography | 2012 | 1 | 4 | 76-81 | 10.2478/v10164-012-0059-0 | Fatigue of Aircraft Structures |
| Mirosław Rodzewicz 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | AIRWORTHINESS TESTS OF THE UAV STRUCTURE − FATIGUE ISSUES | The paper presents investigations undertaken in order to support developing the UAV airworthiness requirements, in particular those concerning fatigue aspects. Knowledge about UAVs load spectra is of vital importance for fatigue issues. The results of preliminary research are presented in this paper. A description of the load spectrum processing is given, starting from filtering the input-data, and then either counting the load signal transfers or implementing the Rainflow Counting algorithm and presenting the results in the form of a transfer array or halfcycles array. This description is illustrated by three examples of flight tests of 4-meter class UAVs, designed at Warsaw University of Technology. They concern flights controlled in a manual and automatic way in order to show differences between the LSs for such control modes. Besides the LS processing, a method for statistical analysis of load spectra from several flights is also presented to address the important problem of LS dispersion. Finally, there are shown selected tests of the UAV structure elements for which load spectra may have a crucial importance. | UAV loads, load spectrum, manual control, autopilot | 2012 | 1 | 4 | 82-93 | 10.2478/v10164-012-0060-7 | Fatigue of Aircraft Structures |
| Michał Sałaciński 1 Magdalena Zabłocka 1 Piotr Synaszko 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | USING SANDBLASTING AND SOL GEL TECHNIQUES FOR THE PREPARATION OF A METAL SURFACE AND THEIR EFFECTS ON THE DURABILITY OF EPOXY-BONDED JOINTS | The epoxy-bonded joints are widely employed in aerospace in the Composite Patch Bonded Repair (CPBR) method used for repair metallic and composite structures. The properties of epoxy usually meet the mechanical and environmental requirements, but the durability of bonded joints depends also on the surface preparation. The most common techniques used for the surface preparation are Forest Product Laboratory’s (FPL) technique and Phosphoric Acid Anodizing (PAA). Both methods ensure very good adhesion but they have some disadvantages. They require the application of toxic and aggressive acids, dangerous for the operator. Also, the use of acids for cleaning the surfaces can cause corrosion. The sandblasting treatment of metal surfaces ensures quite good adhesion. This technique requires neither specialist equipment nor the use of toxic substances. Recommended by the Royal Australian Air Force (RAAF) the technique is also used by the Air Force Institute of Technology. Sol Gel is a new product developed for the treatment of metal surfaces before bonding. It is not hazardous for the operator and it does not cause corrosion due to its specific chemical composition. The article describes the behavior of bonded joints between two metal surfaces prepared using sandblasting and Sol Gel. The investigations were carried out in various environment conditions according to the ASTM Standards. | brak | 2012 | 1 | 4 | 94-99 | 10.2478/v10164-012-0061-6 | Fatigue of Aircraft Structures |
| Szymczyk Elżbieta 1 Bogusz Paweł 1 Sławiński Grzegorz 1 Jachimowicz Jerzy 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | NUMERICAL ANALYSIS OF MATERIAL AND MANUFACTURING FACTORS IN RIVETED JOINTS UNDER THE IMPERJA PROJECT | The aim of the project was to improve fatigue performance of riveted joints in airframes. Fatigue strength of a joint depends on structural, material and manufacturing factors. The project involved numerical and experimental analysis of material factors and manufacturing imperfections. The paper deals with the analysis of material structure and properties by means of the optical and SE methods. Static monotonic tests for sheet and rivet materials were carried out. ARAMIS optical system was used for the study of deformation and strain fields in the material during loading. This tool offers the possibility of a non-contact measurement with 3D image correlation methods (digital image correlation, DIC) using high-resolution digital CCD cameras. In ductile materials (such as aluminium alloy), subjected to appropriate loading conditions, voids may form, which grow and coalesce leading to crack formation and potential failure. A micro crack may be initiated at the inclusion particles and then voids grow around it. Experimental studies showed that these processes are strongly influenced by hydrostatic stress (Gurson’s material model). SEM analysis of material structure was carried out after performing static tests. In the paper, the authors present the influence of a material model on the results of numerical simulation of the tensile loaded samples with open and riveted holes. The application of Gurson’s material model allows observation of crack growth in the sample cross-section and determination of the sheet rupture as the moment when constraint force decreases to zero (material separation occurs). | brak | 2012 | 1 | 4 | 100-113 | 10.2478/v10164-012-0062-5 | Fatigue of Aircraft Structures |
| Lucjan Witek 1 | 1) Rzeszów University of Technology, al. Powstańców Warszawy 12, 35-029 Rzeszów, Poland | NUMERICAL SIMULATION OF FATIGUE FRACTURE OF THE TURBINE DISC | This paper presents the results of the crack propagation analysis of an aircraft engine turbine disc. In the first part of the work the finite element method was used for calculation of the stress state and the stress intensity factor (SIF, KI, K-factor) in the turbine disc with an embedded quarter-elliptical corner crack, subjected to low-cycle thermo-mechanical fatigue. To refine the Kfactor calculation, specially degenerated finite elements were used. These elements provide stress singularity suitable for the linear-elastic material of the disc. The performed calculations yielded the stress intensity factor KI for different crack sizes. Subsequently, K parameter was determined as a difference of the KI values calculated for the turbine’s speeds equal to 6373 and 14200 RPM. Based on the Paris-Erdogan equation and the obtained K values, the fatigue crack growth plot for the turbine disc subjected to complex thermo-mechanical loads was determined. | brak | 2012 | 1 | 4 | 114-122 | 10.2478/v10164-012-0063-4 | Fatigue of Aircraft Structures |
| Mirosław Witoś 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE MMM EXPERT SYSTEM: FROM A REFERENCE SIGNAL TO THE METHOD VALIDATION | This paper presents the first step in the methodological approach to the validation of the metal magnetic memory (MMM) method in the non-destructive testing (NDT) applications and in the systems used for diagnosis of early stages of material fatigue in mechanical constructions (structural health monitoring, SHM, and prognosis health management, PHM). The study is focused on the properties of the external natural source of magnetisation of the object under MMM examination and the impact of the magnetisation components. The precise data obtained from measurements of the Earth's geomagnetism (from ground stations and satellites) and the revised model of the Earth's magnetism can be applied in order to calibrate high sensitivity magnetic field sensors, validate the measurement results and extend the functional capacity of the MMM method. | geomagnetic field, magneto-mechanical effects, numerical model, SHM | 2012 | 1 | 4 | 123-140 | 10.2478/v10164-012-0064-3 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | ANALYSIS OF THE QUASI-STATIC RIVETING PROCESS FOR 90° COUNTERSUNK RIVET | Riveting is the most commonly used method of joining sheet metal components of the aircraft structure. The riveted joints are critical areas of the aircraft structure due to severe stress concentrations and effects such as fretting and secondary bending. The most spectacular and wellknown evident of this was the accident of Boeing B737 of Aloha Airline in 1988, when during the flight at altitude of 7300 m a large part of fuselage skin was removed due to explosive decompression. The investigation showed that the reason for this accident was widespread fatigue damage of riveted joints. This accident was an impulse for establishing many research programs around the world focused on fatigue of riveted joints. In the Netherlands, the University of Technology in Delft was one of active centres where fatigue of riveted joints was a subject of numerous investigations and PhD dissertations, among other the one presented by R.P.G. Müller [1]. He showed that there is strong correlation between riveting force and fatigue life of riveted joints. In the case of three-rows riveted joints assembled with the squeezing force value (driven head dimension) according to the industrial manual fatigue life varied between 39 630 cycles for minimum and 95 200 for nominal squeezing force values. For high squeezing force fatigue life of joint was 446 413 (fig. 1). | brak | 2012 | 1 | 4 | 141-156 | 10.2478/v10164-012-0065-2 | Fatigue of Aircraft Structures |
| Magdalena Zabłocka1 Michał Sałaciński1 Piotr Synaszko1 Sylwester Kłysz1,2 | 1) Air Force Institute of Technology, ul. Ks. Boleslawa 6, 01-494 Warsaw, Poland 2) University of Warmia and Mazury, ul. Oczapowskiego 2, 10-719 Olsztyn, Poland | THE EFFECT OF CURE CYCLE TIME ON THE PROPERTIES OF EPOXY-BONDED JOINTS | This paper presents the results of the study of the properties of epoxy-bonded joints. Depending on the parameters of cure cycles the epoxy adhesive film has got various mechanical properties. When it is possible to use cure parameters suggested in the data sheet of the adhesive film the best results are obtained. However, in aerospace applications the cure cycle depends on the thermal resistance of other aircraft elements including electrical equipment, cables, etc., and is different from the recommended in the data sheet. Composite Patch Bonded Repair (CPBR) is a special methodology, where the patch cure cycle and the bonding process must be carried out in one operation. The adhesive film cure cycle parameters depend on the prepreg cure cycle parameters. The purpose of this research is to define the influence of a prolonged cure cycle of the adhesive film on the bonded layer strength properties. The metal surface of the specimen has been prepared for bonding by sandblasting and the use of Corrosion Inhibiting Primer BR 127. The tests were performed with the use of Structural Adhesive Film AF 163-2 and two types of cure cycles: the cycle recommended by the data sheet - 121ºC/60 min and the prolonged one - 121ºC/105 min. After the cure cycle the thickness of the bonded layer was measured. Both specimens were comparatively tested during the following strength tests of the bonded layer: static breaking tests using the wedge and the shear strength investigations. The surface of the bonded layer was observed during the tests by an electronic microscope (100x, 200x), which made it possible to demonstrate the effect of the cure cycle on the porosity and observe the nature of the bonded layer damage – de-cohesive and de-adhesive. | brak | 2012 | 1 | 4 | 157-161 | 10.2478/v10164-012-0066-1 | Fatigue of Aircraft Structures |
| Hiroyuki Terada 1 | 1) Japan Aerospace Technology Foundation, Tokyo, Japan | STRESS INTENSITY FACTOR ANALYSIS AND FATIGUE BEHAVIOR OF A CRACK IN THE RESIDUAL STRESS FIELD OF WELDING | This paper deals with the behavior of a crack in the residual stress field induced by the butt weld in a wide plate. It is known that the distribution form of residual stress has similarities regardless of the welding process, although the size and the magnitude of the residual stress depend largely on the welding process. Stress intensity factor and stress redistribution induced by the crack extension were calculated for a crack with arbitrary length and location. The stress redistributions caused by crack extension obtained by the present analysis showed good agreement with the experimental data. Fatigue crack propagation behavior in the residual stress field reported by Glinka was also examined from ΔK point of view. The effect of residual stress on the fatigue crack propagation rate is considered to be the effect of varying mean stress. It was shown that fatigue crack propagation rate is estimated by the following equation with reasonable accuracy. In the above equation, material constants C and α of Paris’s law are experimentally obtained by using specimens without the weld joint. | stress intensity factor analysis, crack, residual stress field, butt weld, stress redistribution, fatigue crack, crack propagation | 2011 | 1 | 3 | 5-15 | 10.2478/v10164-010-0032-8 | Fatigue of Aircraft Structures |
| Krzysztof Dragan 1 Piotr Synaszko 1 Michał Sałaciński 1 Adam Latoszek 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | BONDED JOINT MONITORING OF THE COMPOSITE AEROSPACE STRUCTURES WITH THE USE OF NDE AND SHM APPROACH | One of the modern trends in aerospace community is the approach to integrate the sensors with the structure to create the so called „intelligent – smart‟ structures[1]. This approach is known as Structural Health Monitoring (SHM). The use of integrated sensors may allow for monitoring of selected components and also for data comparison and damage development description. In the article, the problem of the bonded joint monitoring will be presented. Moreover, the tests will be conducted and data from NDT and SHM (based on piezoelectric sensors and elastic wave generation) will be presented for the composite aerospace structures such as CFRP. | brak | 2011 | 1 | 3 | 16-21 | 10.2478/v10164-010-0033-7 | Fatigue of Aircraft Structures |
| Sylwester Kłysz 1 Janusz Lisiecki 1 Dariusz Zasada 1 Gabriel Gmurczyk 1 Andrzej Leski 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | PZL-130TC-II FRACTURE MARKERS SOLUTION FOR FULL-SCALE FATIGUE TEST | In the context of PZL-130TC-II full-scale fatigue test, several strategies of fatigue loadings that create fracture surface markings were considered. One block of spectrum is made of 200 flights. By reordering those flights, a block which should create a fracture marker, was developed. It was very important that reordering the load spectrum or adding overloads or underloads did not change spectrum severity. Pilot tests of aluminium alloys specimens were carried out to finalise appropriate marker intervals before commencing full-scale tests. The experiment was conducted with the MTS machine with 810.23 system. The results and conclusions are presented within this paper. | full scale fatigue test, fracture surface marking, Quantitative Fractography | 2011 | 1 | 3 | 22-27 | 10.2478/v10164-010-0034-6 | Fatigue of Aircraft Structures |
| Volodymyr Hutsaylyuk 1 Janusz Mierzyński 1 Dariusz Zasada 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | THE ANALYSIS OF FATIGUE CRACK PROPAGATION IN THE ELEMENTS OF ALUMINUM ALLOY D16CZATW WITH A NOTCH IN THE FORMOF A CYLINDRICAL HOLE | In this work, the fatigue life of specimens made from the aluminum alloy D16CzATW has been determined. To this aim, flat specimens with notches in the form of cylindrical holes made by drilling and reaming have been investigated. The research was carried out under the conditions of constant-amplitude bending at the stress ratio of R = -1. The results obtained were compared with the fatigue life of specimens with calibrated holes and specimens without notches. Fatigue life was determined for specimens plated on both sides and those without this protecting layer. Very large differences in fatigue resistance were observed. These differences can be explained by the negative effect of the brittle protecting layer on the fatigue crack initiation process. A complex fracture mechanism was observed, in which micro-mechanisms of brittle and ductile fracture were appearing at different stages of fatigue crack propagation. | brak | 2011 | 1 | 3 | 28-41 | 10.2478/v10164-010-0035-5 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Bartosz Korzeniewski 1 Merja Hakanen 2 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Stresstech Oy, Finland | METHODOLOGY OF RESIDUAL STRESS MEASUREMENTS FOR RIVET JOINTS | The methods and good practice in XRD measurements are presented in this paper. The paper concerns the specimens made of 2024-T3 aluminium alloy plates joint together by rivets. The presented methodology can by divided into two parts: (1) general rules of XRD measurements on 2024-T3 aluminium alloy - choosing the diffraction angle, time of exposure on X-ray radiation, diameter of X-ray spot, etc. and (2) rules applied to riveted specimens - geometrical analysis of the specimen and movements of the goniometer which allow to obtain proper results of stress measurement. Short information about theoretical bases and influence of protective layers on XRD measurement is also included. In the end of the paper the additional equipment called the slit is presented, which allow to perform measurements on flat and cylindrical surfaces with higher resolution. | brak | 2011 | 1 | 3 | 42-52 | 10.2478/v10164-010-0036-4 | Fatigue of Aircraft Structures |
| Łukasz Kornas 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | ANALYSIS OF THE POSSIBILITY TO ASSESS THE OCCURRENCE OF HIDDEN CORROSION IN LAP JOINTS USING ACTIVE THERMOGRAPHY | The article details the NDT technique of pulse thermography used for objective diagnosis of riveted lap joints construction. The degradation of materials manifesting in corrosion is inherent in the process of aircraft operation. One type of corrosion is galvanic corrosion occurring in the overlap joints (known as hidden corrosion). As a result of the potential difference between the two layers of the aluminum alloy skin, there occurs the phenomenon of oxidation of the material, producing corrosion products in the form of oxide compounds characterized by heat properties different than those of the base material. Active thermography techniques allow observing infrared energy, which changes due to the difference of thermal properties of the tested materials. | brak | 2011 | 1 | 3 | 53-56 | 10.2478/v10164-010-0037-3 | Fatigue of Aircraft Structures |
| Jerzy Kozak 1 | 1) Institute of Aviation, al. Krakowska 110/114, 02-256 Warsaw, Poland | THE EFFECT OF ELECTROCHEMICAL MACHINING ON THE FATIGUE STRENGTH OF HEAT RESISTANCE ALLOYS | Electrochemical Machining (ECM) provides an economical and effective method for machining high strength, heat-resistant materials into complex shapes such as compressor and turbine blades, dies, molds and micro cavities. ECM is performed without physical contact between the tool and the workpiece in contrast to the mechanical machining, and without strong heating in the machining zone in distinction to the methods such as EDM. Therefore, no surface metal layer with mechanical distortion, compressive stresses, cracks, and thermal distortion forms in ECM. ECM is often used even for removing a defective layer, which has been formed in EDM, with the aim to improve the surface integrity. However, sometimes the intergranular attack occurs in ECM. This may reduce the performance of machined parts and lead to the decreasing of fatigue strength. In this paper, the effects of ECM on fatigue strength of heat resistant alloys such as nickel-base alloys and titanium alloys are presented. The problems of the intergranular attack, hydrogen embrittlement and surface roughness as result of ECM parameters are described. | anodic dissolution, current density, hydrogen embrittlement, intergranular attack, fatigue strength | 2011 | 1 | 3 | 57-63 | 10.2478/v10164-010-0038-2 | Fatigue of Aircraft Structures |
| Marcin Kurdelski 1 Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | CRACK GROWTH ANALYSIS OF THE LANDING GEAR PULL ROD OF THE FIGHTER JET AIRCRAFT | This paper describes the problem of searching for the causes of damage in the form of rupture of a strength member of the main landing gear. There have been two incidents noted which both occurred during hangar storage. It should be pointed out that the two occurrences mentioned concern a particular aircraft currently in operation, and that these incidents occurred a few days after the last flight. This article presents part of the investigation process needed to determine the causes of cracks in the test item. The crack growth analysis of the pull rod was performed using the NASGRO software. In order to perform the calculations, the information was gathered during previously conducted material studies and flight tests. | crack growth, fatigue, flight tests, landing gear | 2011 | 1 | 3 | 64-73 | 10.2478/v10164-010-0039-1 | Fatigue of Aircraft Structures |
| Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | SERVICE LIFE ASSESSMENT PROGRAM OF PZL-130 ORLIK TC-II STRUCTURE | The following paper concerns the structural integrity program (SEWST) for the PZL-130 Orlik TCII trainer aircraft. The origin of the program is defined as well as the most important tasks necessary to fulfill the assumed goal. keywords: SEWST, Full Scale Fatigue Test, flight loads, teardown inspection | brak | 2011 | 1 | 3 | 74-77 | 10.2478/v10164-010-0040-8 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | FLIGHT LOADS ACQUISITION FOR PZL-130 ORLIK TC-II FULL SCALE FATIGUE TEST | The following article presents the research conducted under a complex structure integrity program for PZL-130 "Orlik" TC-II trainer aircraft. The aim of the research was to obtain the actual flight loads characteristic for the Polish Air Force which further on will be used to determine characteristic load spectrum for the Full Scale Fatigue Test purpose. This paper presents the methodology as well as a brief discussion of the obtained results. | Full Scale Fatigue Test, flight loads, strain measurement | 2011 | 1 | 3 | 78-85 | 10.2478/v10164-010-0041-7 | Fatigue of Aircraft Structures |
| Mirosław Rodzewicz 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | INVESTIGATION INTO FATIGUE BEHAVIOUR OF METAL-COMPOSITE GLUE CONNECTION | The paper presents the results of experimental investigations into fatigue properties of metal and CFRP-composite glued joints. The object of investigation was adhesive joints between metal sheets made from iron alloy 30HGS (popular steel in the Polish aviation industry) and CFRP orthogonal reinforced sheets made from 10 layers of SIGRATEX CE3208 pre-preg. The main adhesive was the WK-3 glue (applied in the form of 0.2 mm thin foil) while the DP-490 - liquid epoxy glue was used as technological aid for specimen manufacturing. Two kinds of specimens were prepared and tested: single-lap joints and double-lap joints. The paper presents S-N curves for both kinds of those specimens. Besides fatigue life of the glued joints, the interest was focused on the NDT tests regarding damage propagation inside the glue-connection. The paper presents several C-scans made at different stages of fatigue testing. It has been found that the damage occurs almost equally in the whole volume of the glue layer (contrary to the expectation following from the physical model of the glue-connection internal loading). The results of experiments regarding thermal effect of cyclic loading of the glued joints are also described. It has been found that this effect could be used as an important parameter for diagnostics purposes of the glued joints. | brak | 2011 | 1 | 3 | 86-102 | 10.2478/v10164-010-0042-6 | Fatigue of Aircraft Structures |
| Michał Sałaciński 1 Piotr Synaszko 1 Michał Stefaniuk 1 Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | MONITORING OF CRACK GROWTH IN A STRUCTURE UNDER A COMPOSITE PATCH | In civil as well as in military aviation, boron, carbon and aramid fiber reinforced composites are employed for the repair of metal structures. After such composite bonded repairs, the monitoring of the repaired structure along with the composite patch and its bond is necessary. The paper describes the possibilities of utilizing NDT methods for periodical check-ups and examinations. Also, a novel approach to continuous monitoring of the repaired structure is presented. | brak | 2011 | 1 | 3 | 103-111 | 10.2478/v10164-010-0043-5 | Fatigue of Aircraft Structures |
| Mirosław Witoś 1 Michał Stefaniuk 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | COMPRESSOR BLADE FATIGUE DIAGNOSTICS AND MODELLING WITH THE USE OF MODAL ANALYSIS | This paper investigates the diagnostic and research aspects of the compressor blade fatigue. The authors have reviewed the characteristics of different modes of metal blade fatigue (LCF, HCF, VHCF). The polycrystalline defects and impurities influencing the fatigue, along with their related surface finish techniques, have been taken into account. The experimental methods of structural health assessment have been considered. The Tip Timing (TTM), Experimental Modal Analysis (EMA) and Metal Magnetic Memory (MMM) provide information on the damage of the diagnosed object (compressor blade). It has been proven that the shape of resonance characteristics gives an ability to determinate if fatigue or a blade crack is concerned. Early damage symptoms, i.e. modal properties of material strengthening and weakening phases have been described. The experimental verification of the FEM model is presented based on a large body of experimental data collected by the author. | compressor blade, damage, fatigue, modal analysis, lattice-spin coupling, FEM | 2011 | 1 | 3 | 112-133 | 10.2478/v10164-010-0044-4 | Fatigue of Aircraft Structures |
| Lucjan Witek 1 | 1) Rzeszów University of Technology, Al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland | EXPERIMENTAL AND NUMERICAL CRACK INITIATION ANALYSIS OF THE COMPRESSOR BLADES WORKING IN RESONANCE CONDITIONS | This paper presents the results of a complex experimental and numerical crack initiation analysis of the helicopter turbo-engine compressor blades subjected to vibrations. A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects as well as those with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. The obtained results were next used as an input data into crack initiation (–N) analyses performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis, the different methods such as: Neuber elastic-plastic strain correction, linear damage summation and Palmgreen-Miner rule were utilized. As a result of –N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material were calculated using the Baumel-Seeger and Muralidharan methods. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of the work, the finite element results were compared with the results of experimental vibration HCF tests performed for the compressor blades. | brak | 2011 | 1 | 3 | 134-153 | 10.2478/v10164-010-0045-3 | Fatigue of Aircraft Structures |
| Lucjan Witek 1 | 1) Rzeszów University of Technology, Al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland | STRESS INTENSITY FACTOR CALCULATIONS FOR THE COMPRESSOR BLADE WITH HALF-ELLIPTICAL SURFACE CRACK USING RAJU-NEWMAN SOLUTION | This paper presents results of the stress intensity factor calculations for the compressor blade including a half-elliptical crack, subjected to vibration. In this analysis, the Raju-Newman empirical solution for stress intensity factor calculations in the rectangular plate with a halfelliptical flaw was used. The bending stress used in the Raju-Newman solution was computed for the real blade using the finite element method. The K-factor values were calculated only at one point of the crack front, where the crack tip contacts the free surface, because the crack length during experimental investigations was measured just in this direction. In order to determine the stress intensity factors for different crack sizes, ten diverse flaws in the blade were defined. Results of the experimental fatigue tests performed for the blade without preliminary defects showed that the cracks developed from the convex blade surface. On the blade fracture, the beach marks typical of the fatigue damage were visible. The dimensions of cracks in the rectangular plate were defined based on the beach marks shape. In the next part of the work, the stress intensity factor values were used as an input data into the Paris-Erdogan equation. As a result of this calculation, the crack growth rate for the compressor blade vibrating at constant amplitude was estimated. The results obtained were finally compared with the results of the experimental crack growth analysis performed for 1st stage compressor blades of the helicopter turbo-engine. | brak | 2011 | 1 | 3 | 154-165 | 10.2478/v10164-010-0046-2 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | EXPERIMENTAL AND NUMERICAL STUDY OF STRAIN PROGRESS DURING AND AFTER RIVETING PROCESS FOR BRAZIER RIVET AND RIVET WITH COMPENSATOR – SQUEEZING FORCE AND RIVET TYPE EFFECT | The paper presents the experimental and numerical investigation of the stress and strain field around the rivet after the riveting process. The measurements were carried out with the X-ray diffractometer and strain gauges on the sheet surface near the driven head. The axisymmetric and 3D FEM analyses of the riveting process were performed. The article presents experimental and numerical results for two types of the brazier rivets used in the Polish aerospace industry; the normal rivet (BN-70/1121-06) and the rivet with a compensator (OST 1 34040-79 1). Bare sheets made from 2024 T3 aluminium alloy with the nominal thickness of 1,27 mm and rivets with the diameter of 3 mm and 3,5 mm made from Polish aluminium alloy PA25 were used. The measurements were compared with the FEM calculations. The influence of squeezing force as well as the rivet type on stress and the strain system was investigated. | brak | 2011 | 1 | 3 | 166-190 | 10.2478/v10164-010-0047-1 | Fatigue of Aircraft Structures |
| Robert Baraniecki 1 Małgorzata Kaniewska 1 Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | FATIGUE LIFE ASSESSMENT OF SELECTED STRUCTURAL ELEMENTS OF MI-24 HELICOPTER | In order to ensure the integrity of the structure, it is important to determine the actual loads that act on individual elements and their influence on fatigue life. The article demonstrates how to determine the fatigue life of selected elements of the Mi-24 helicopter. In addition, the work indicates the potential location of damage. In calculations, the actual levels of loads acting on the elements during the flight were used. The entire test was performed using the numerical analysis, which greatly helped reduce the time of the project. Fatigue life was determined using the MSC. FATIGUE program with the Palmgren - Miner linear damage accumulation rule. | brak | 2010 | 1 | 2 | 5-13 | 10.2478/v10164-010-0020-z | Fatigue of Aircraft Structures |
| Krzysztof Dragan 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | STRUCTURAL HEALTH MONITORING APPROACH TO THE AEROSPACE STRUCTURES | In the article only selected information regarding the SHM applications has been presented. These applications are associated with damage detection and damage growth monitoring. That approach has got crucial influence on the aircraft maintenance procedures. SHM ensures higher reliability and safety of the structures as well as repair monitoring. Right now in the AFIT, there is being conducted research work focused on the application of the SHM system for the integration with the aerospace structures for periodical and on-line monitoring. | brak | 2010 | 1 | 2 | 14-18 | 10.2478/v10164-010-0021-y | Fatigue of Aircraft Structures |
| Krzysztof Dragan 1 Łukasz Kornas 1 Adam Latoszek 1 Michał Sałaciński 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | DIAGNOSTICS OF COMPOSITE AIRCRAFT STRUCTURES USING NON-DESTRUCTIVE TESTS WITH THERMOGRAPHIC, ULTRASOUND AND ACOUSTIC METHODS | Control and constant supervision over the technical condition of composite constructions of the aircraft are the activities necessary for the safety of exploitation. Even small damage of the composite aircraft structures, caused mainly by heavy loads and changeable atmospheric conditions, will weaken the structure and may lead to serious accidents. Having this in mind, periodical controls using non-destructive tests are conducted. The most popular methods widely used in aviation are those based on ultrasound and acoustic phenomena occurring in examined structures [2]. Ultrasound method consists in emitting ultrasound waves from a transmitter into the material. The material has defects (borders of connections, delaminations) which are the reflector from which the wave reflects and comes back to the transmitter head. Examination of this phenomenon is based on observing the amplitude volume and direction changes of ultrasound waves and on the time measurements of the wave passing through the examined material [4]. Other techniques used for detecting defects in composite structures are ultrasound resonant techniques based on the measurement of resonant vibrations of a given material. Continuous waves introduced into the material are gained or damped. Amplitude and phase of vibrations on the material surface depend on the flexural modulus and thickness of the material placed under the head [3]. Acoustic impedance is another physical phenomenon used (method-MIA). The method is based on the resistance (dampening) measurement of acoustic waves with a specific volume of the examined material. The above-mentioned non-destructive tests are not the only techniques of examining the composite structures. Due to improvement of composite structures, engineers are forced to implement the latest examination methods. One of these methods is pulsed thermography. This method consists in even activation of the structure by thermal pulse and monitoring changes in temperature distribution of the examined surface, while it is cooling down, by means of the TV camera. Defected areas lose heat much slower and therefore they are characterized by temperature higher than the areas free of material defects [1]. | brak | 2010 | 1 | 2 | 19-22 | 10.2478/v10164-010-0022-x | Fatigue of Aircraft Structures |
| Elżbieta Gadalinska 1 Wojciech Wronicz 1 Jerzy Kaniowski 1 Bartosz Korzeniowski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | CALCULATION AND EXPERIMENTAL VERIFICATION OF RESIDUAL STRESSES IN RIVETED JOINTS USED IN AN AIRFRAME | This paper presents diffraction measurements of residual stresses around the rivet, formed during the riveting process. The measurements were made with the XSTRESS-3000 diffractometer, manufactured by Stresstech Oy. The measurements were carried out on specimens made of bare sheet 2024-T3 alloy, (standard AMS-QQ-250 / 4). The measurement results were compared with the FEM simulation results. The work was performed under the EUREKA IMPERIA project E! 3496. | brak | 2010 | 1 | 2 | 23-36 | 10.2478/v10164-010-0023-9 | Fatigue of Aircraft Structures |
| Michal Jasztal 1 Dorota Kocanda 1 Henryk Tomaszek 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | PREDICTING FATIGUE CRACK GROWTH AND FATIGUE LIFE UNDER VARIABLE AMPLITUDE LOADING | A probabilistic approach to the description of fatigue crack growth and fatigue life estimation of a component subjected to variable amplitude loading is presented in the paper. The core of the model is a differential equation originated from the Paris formula. In order to consider the influence of overload-underload cycles existing in an exploitive load spectrum on crack growth rate for an aeronautical aluminum alloy sheet, the modified Willenborg retardation model was applied. | brak | 2010 | 1 | 2 | 37-51 | 10.2478/v10164-010-0024-8 | Fatigue of Aircraft Structures |
| Sylwester Klysz 1 Gabriel Gmurczyk 1 Janusz Lisiecki 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | INVESTIGATIONS OF SOME PROPERTIES OF MATERIAL SAMPLES TAKEN FROM THE AIRCRAFT WITHDRAWN FROM SERVICE | Materials used in aircraft structures have (should have) certificates confirming their quality. Nowadays, in majority of cases, the symbols of materials used in construction of aircraft give detailed information about their mechanical properties. This general material data is gathered in the widely available engineering material data bases. In the case of materials used in Polish aviation several decades ago, there is no reliable material data crucial for crack propagation estimation or fatigue life estimation among others. Examinations conducted in many different research institutes are not systematized and are not gathered in a remotely accessible data base. As aging aircraft are concerned, the influence of service time (often exceeding thirty years) on the overall material properties is a very important factor. It may be too crude estimation to use standard material properties when it comes to aging aircraft fleet. Some experimental works concerning this topic are published from time to time and they are always very welcome. In the Air Force Institute of Technology experimental tests were carried out to determine some specific properties of the materials used in the PZL-130 Orlik aircraft structure. The samples were obtained from aircraft withdrawn from service. This enabled estimating the difference in material properties over time. The following tests were conducted during the experiments: - fatigue tests (crack propagation examination) - static tests. The analyzed material was taken from the central upper part of the aircraft wing. The experiment was conducted with the MTS machine with the 810.23 system. | brak | 2010 | 1 | 2 | 52-58 | 10.2478/v10164-010-0025-7 | Fatigue of Aircraft Structures |
| Marcin Kurdelski 1 Łukasz Obrycki 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE CRACKS PROPAGATION CALCULATIONS IN THE PZL-130 ORLIK STRUCTURE | The article presents the results of research carried out under a research project on the evaluation of fatigue life. The subject of the analysis was the critical elements of the PZL-130 Orlik. The numerical crack growth analyses were performed using the NASGRO equation. The Orlik aircraft are mainly used for the basic pilot training in the Polish Air Force. Each airplane is equipped with a digital flight data recorder. The record of more than 36000 flight hours is the basis for numerical analysis of fatigue life. | brak | 2010 | 1 | 2 | 59-68 | 10.2478/v10164-010-0026-6 | Fatigue of Aircraft Structures |
| Andrzej Leski 1 Łukasz Obrycki 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | REPRESENTATIVE LOAD SEQUENCE FOR THE PZL-130 ORLIK | Variable loads affect an aircraft throughout its operation. Some of them are determined by maneuver loads others are random eg. gust loads. Each particular flight has its own load sequence. Two equivalent flights (the same mission) performed by the same pilot during similar weather conditions are different. The load sequence acting on a structure during flight is recorded by an onboard flight recorder. An increase in the recorder accuracy emphasizes the differences between flights. Originally, the only parameter used to perform fatigue load assessment was the flight time. In this case it is easy to show similarity between flights. Since nz-cycle recorders were applied the flight loads have been monitored more precisely. The clear view on the flight loads is possible if the aircraft is equipped with a multi-channel flight data recorder. The digital flight data recorder can store the load history, which is very important for fatigue calculation. The load history informs of the load cycle sequence and a retardation model in fatigue calculation can be applied. The whole usage history of aircraft is hard to collect because of the lack of data. Even if all the data were collected it would be impractical to use them because of a large number of data collected for each aircraft during its service life. If the load history consists of such a large number of data, it cannot be used either for numerical calculation or laboratory fatigue tests. The representative load sequence for a selected aircraft or helicopter population has been an area of interest for scientists for several years as well as the topic of scientific projects. Among the developed representative load sequence are: - Falstaff - Turbistan - Helix - Felix A representative load sequence can be used for fatigue calculation and for crack growth analysis, which are performed for aircraft structural integrity purposes. This sequence can also be used for a full scale fatigue test or for laboratory tests of aircraft parts or specimens. These activities support aircraft reliability and safety. | brak | 2010 | 1 | 2 | 69-78 | 10.2478/v10164-010-0027-5 | Fatigue of Aircraft Structures |
| Piotr Reymer 1 Andrzej Leski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | FATIGUE LIFE ESTIMATION OF THE TAIL BOOM AND VERTICAL STABILIZER OF MI-24 HELICOPTER | The aim of this work was to estimate fatigue life of the Mi-24 helicopter tail boom and vertical stabilizer sheathing. The analysis was based on a numerical model of the helicopter airframe crucial to obtain stress fields under defined loads and to estimate fatigue life. In order to do so, the load spectrum, specific for Polish army helicopters, was obtained by means of strain gauge measurements during a series of experimental flights. Data collected during flights was post-processed to create a characteristic ten hour spectrum that would statistically represent the flight profile for Polish Army Mi-24 helicopters. The third crucial element of the analysis was the safe S-N curve that was created on the basis of 2024-T3 aluminum S-N curve. Two factors were introduced in order to change the curve in a way that would guarantee a higher level of certainty that the outcome is not overrated. As a result of this analysis the total fatigue life was estimated including the list of critical locations in which fatigue damage is prone to occur. These regions are going to be carefully examined during scheduled inspections. | brak | 2010 | 1 | 2 | 79-86 | 10.2478/v10164-010-0028-4 | Fatigue of Aircraft Structures |
| Mirosław Rodzewicz 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | ESTIMATION OF FATIGUE PROPERTIES OF COMPOSITE STRUCTURES | The paper presents the proposal of a simplified method of fatigue properties estimation for polymer composite structures. | brak | 2010 | 1 | 2 | 87-97 | 10.2478/v10164-010-0029-3 | Fatigue of Aircraft Structures |
| Michał Salacinski 1 Piotr Synaszko 1 Robert Olszak 2 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland 2) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | DIAGNOSIS AND REPAIR TECHNOLOGY OF DAMAGED ELEMENTS OF CASA AIRCRAFT | Recently Polish Air Force has been equipped with new types of aircraft. New aircraft have many elements made of composites. Composites enable increasing performance but also pose new challenges. One of these challenges is the necessity of repairing after damage. This paper presents the results of the non-destructive inspection (MIA, conductivity, optical measurement ) of the C295 plane after damage. Some parts made of composites and metal were damaged. In this paper, the authors propose a technology of repairing damaged parts. | brak | 2010 | 1 | 2 | 98-105 | 10.2478/v10164-010-0030-x | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Wojciech Wronicz 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | NUMERICAL ANALYSIS OF RIVETED LAP JOINT USED IN AIRCRAFT STRUCTURES | The paper presents the results of FEM analysis of two rivet lap joints loaded with tension. The joint consists of two sheets with dimensions of 125x60 mm and nominal thickness of 1.2 mm made of 2024-T3 clad alloy ASNA 3012 and two rivets (fig. 1).The countersunk rivets made of PA25 alloy were used. The diameter of the rivets was 3,5 mm and angle 120º, according to the BN70/1121-05 standard. Due to its symmetry, only a half of the joint was analysed. Nonlinear material models were used and contact phenomena between sheets, rivets and tools were taken into account. The analysis involved the riveting process as well as tensile loading of the joint. MSC MARC software was used. The article presents the numerical analysis of the joint. The work of a rivet was studied. The results obtained up to date were discussed as well as the difficulties encountered. Experimental verification of the calculation with strain gauges is planned. The financial support from Ministry of Science and Higher Education under the contract No. 59/EUR/2006/02 is gratefully acknowledged. | brak | 2010 | 1 | 2 | 106-116 | 10.2478/v10164-010-0031-9 | Fatigue of Aircraft Structures |
| Petr Augustin 1 | 1) Brno University of Technology, Brno, Czech Republic | SIMULATION OF FATIGUE CRACK GROWTH IN INTEGRALLY STIFFENED PANELS UNDER THE CONSTANT AMPLITUDE AND SPECTRUM LOADING | The paper describes methodology of numerical simulation of fatigue crack growth and its application on integrally stiffened panels made of 2024-T351 aluminium alloy using high speed cutting technique. Presented approach for crack growth simulation starts by the calculation of stress intensity factor function from finite element results obtained using MSC.Patran/Nastran. Subsequent crack growth analysis is done in NASGRO and uses description of crack growth rates either by the Forman-Newman-de Koning relationship or by the table lookup form. Three crack growth models were applied for spectrum loading: non-interaction, Willenborg and Strip Yield model. Relatively large experimental program comprising both the constant amplitude and spectrum tests on integral panels and CCT specimens was undertaken at the Institute of Aerospace Engineering laboratory in order to acquire crack growth rate data and enable verification of simulations. First analyses and verification tests of panels were performed under the constant amplitude loading. For predictions of crack growth using the spectrum loading a load sequence representing service loading of the transport airplane wing was prepared. Applied load spectrum was measured on B737 airplane within the joint FAA/NASA collection program. The load sequence is composed of 10 flight types with different severity analogous to the standardized load sequence TWIST. Before application on the stiffened panels a calculation of crack growth under the spectrum loading was performed for simple CCT specimen geometry. The paper finally presents comparison of simulations of fatigue crack propagation in two-stringer stiffened panel under the spectrum loading with verification test carried out in the IAE lab. The work was performed within the scope of the 6th Framework Programme project DaToN - Innovative Fatigue and Damage Tolerance Methods for the Application of New Structural Concepts. | brak | 2009 | 1 | 1 | 5-19 | 10.2478/v10164-010-0001-2 | Fatigue of Aircraft Structures |
| Zdzisław Bogdanowicz 1 Dorota Kocańda 1 Janusz Torzewski 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | CAPACITY OF FRACTOGRAPHIC ANALYSIS FOR LOAD-TIME ISTORY RECONSTRUCTION AND FATIGUE CRACK GROWTH RATE ESTIMATION FOR THE 2024-T3 ALUMINIUM ALLOY | The subject of the paper is the considerations for the feasibility of load time history reconstruction on the basis of microfracture analysis for a failed component made of 2024-T3 aluminium alloy that operates under variable amplitude loading. For this goal three different variable amplitude load sequences with single and multiple overloads and underloads were applied to investigate crack growth rate and to examine the images of fatigue striations on the fracture surface of a component. These loads are employed when simulating the fatigue crack behaviour in aeronautical alloys. Microfracture analysis was also used either for learning the interaction of variable amplitude loading for crack growth rate in 2024-T3 alloy or for establishing the relation between surface crack and crack depth growth. | brak | 2009 | 1 | 1 | 20-36 | 10.2478/v10164-010-0002-1 | Fatigue of Aircraft Structures |
| Krzysztof Dragan 1 Piotr Szynaszko 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | IN-SERVICE FLAW DETECTION AND QUANTIFICATION IN THE COMPOSITE STRUCTURES OF AIRCRAFT | Taking into consideration the increased usage of composites for aircraft structures there is a necessity for gathering information about structural integrity of such components. During the manufacturing of composites as well as during in service and maintenance procedures there is a possibility for damage occurrence. There is a large number of failure modes which can happen in such structures. These failure modes affect structural integrity and durability. In this work modern approach for detection of composites damage detection such as: delaminations, disbonds, foreign object inclusion and core damage has been presented. This detection is possible with the use of advanced P-C aided Non Destructive Testing methods. In the article nondestructive testing results for the composite vertical tail skins on MiG-29 aircraft will be delivered as well as some results of F-16 horizontal stabilizer and W-3 helicopter main rotor blades. Moreover some results of the composite honeycomb and sandwich structures will be presented based on the materials used in the construction of gliders and small aircraft. Factors affecting structural integrity and durability of the composites will be highlighted as well as necessity of the inspection with the use of modern NDT techniques. At the end some effort with Structural Health Monitoring connected with possibility of condition monitoring of composites will be presented. | brak | 2009 | 1 | 1 | 37-41 | 10.2478/v10164-010-0003-0 | Fatigue of Aircraft Structures |
| Ion Fuiorea 1 Daniela Bartis 1 Roxana Nedelcu 1 Florin Frunzulica 2 | 1) Military Technical Academy, Bucuresti, Romania 2) Polytechnic University, Bucuresti, Romania | NUMERICAL MODELS FOR FATIGUE CRACK EVOLUTION STUDY | The paper presents some considerations regarding to the numerical simulation of the behaviour of the riveted structures in fatigue loading conditions. In order to estimate the stress intensity factor, “k”, different constitutive laws for the materials were considered. Choosing different contours for “J” integral calculation, some simplified models were studied. The final numerical results were analysed with respect to the physical tests. | brak | 2009 | 1 | 1 | 42-49 | 10.2478/v10164-010-0004-z | Fatigue of Aircraft Structures |
| Ion Fuiorea 1 Daniela Bartis 1 Roxana Nedelcu 1 Adrian Mocanu 2 | 1) Military Technical Academy, Bucuresti, Romania 2) Polytechnic University, Bucuresti, Romania | THE RIVET PARAMETER INFLUENCE IN FATIGUE STRENGTH | The paper deals with the experimental analysis of the influence of the rivet parameters upon the fatigue strength of aircraft structures. Different riveted samples were tested on fatigue machine taking into account the diameter of the rivet and the forming pressure influence. By superposing the resulting Wöhler curves on the same graphic, some interesting conclusions were pointed. | brak | 2009 | 1 | 1 | 50-57 | 10.2478/v10164-010-0005-y | Fatigue of Aircraft Structures |
| Elżbieta Gadalińska 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | MEASUREMENTS PARAMETERS OPTIMISATION FOR X-RAY DIFFRACTOMETRY MEASUREMENTS OF STRESS STATE AROUND THE RIVETS | X-ray diffractometry is one of the basic methods of stress measurement. This method was used to measure stress distributions around rivets as described further in this paper. There were two types of riveted samples, six types of samples made of rivet wire (after different types of treatment) and a aluminium sheet sample with three measurement areas: plate with both cladding and anodized layer, plate after removing the anodized layer and plate after removing both cladding and anodized layer. Riveted samples were prepared to measure the stress distribution around the rivets and the samples of wire and the plate with three areas were prepared to check the effect of different types of treatment on stress state. | brak | 2009 | 1 | 1 | 58-62 | 10.2478/v10164-010-0006-x | Fatigue of Aircraft Structures |
| Volodymyr Hutsaylyuk 1 Lucjan Śnieżek 1 Volodymyr Hlado 2 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland 2) Ternopil National Ivan Pul'uj Technical University, Ternopil, Ukraine | FATIGUE DAMAGE OF RIVET JOINTS IN THE CONDITION OF STABLE CYCLIC LOAD | The article is devoted, to the attempt of working out of a method for determination of period of exploitation for riveting connections with microdefects on the initial stage and propagation of crack to the moment of appearances to the surface. The tested material used aluminum alloy 2024-T3. Experimental researches are realized on flat specimens from an aluminum alloy 2024-T3 with the row of openings for riveting: without riveting (initial state), with a removal of riveting, and also the specimens connected by riveting at stable amplitude loading (tension, σ=100 MPpa) at the coefficients of asymmetry of cycle of R: 0,15;0,3 and 0,5. An origin of local damages in the sheets, and also in riveting connections was controlled by the use of vortex-current defectoscope BD 3-71 with a sensor of a converting type PN-12 MDF 01. Researches of mechanisms of fracture and fatigue were realized with the use of electron scanning microscope of REM of 106I. As a result of these research, information was received about the mechanisms of failure, defined a form and a size of initial damage in appearance in a crack, which can be used as a quality parameter for determination of transitional period of exploitation with microdefects. On the basis of the collected experimental results, statistical description of sizes of local damages was made. | brak | 2009 | 1 | 1 | 63-73 | 10.2478/v10164-010-0007-9 | Fatigue of Aircraft Structures |
| Sylwester Kłysz 1 Janusz Lisiecki 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | STRENGTH TESTING AND ANALYSIS OF FATIGUE CRACK GROWTH IN SELECTED AIRCRAFT MATERIALS | The study has been intended to determine the most essential mechanical and fatigue properties as well as impact strength of the 30HGSNA steel, to gain own data on the above-mentioned characteristics of materials to be used further on in numerical analyses of life estimates of aeronautical structural components. The scope of the study comprised the following assignments: - determination of the most fundamental mechanical properties and impact strength of materials, - low-cycle fatigue testing and evaluation of the Manson-Coffin curves, - high-cycle fatigue testing and evaluation of the Wöhler curves, - investigation into fatigue crack growth rates at constant and variable load-cycle amplitudes (determination of curves da/dN = f(ΔK, R), coefficients in Paris and NASGRO equations, coefficients in the Wheeler models of delay, the value of Kth(R)), - crack toughness testing under the plane-state-of-strain conditions at room temperature (determination of the KIc(R)). The strength/fatigue testing was carried out in the Laboratory for Materials Strength Testing of the AFIT’s Division for Aeronautical Systems Reliability and Safety, the lab being accredited by the Polish Centre for Accreditation (Accreditation Certificate No.: AB 430). | brak | 2009 | 1 | 1 | 74-83 | 10.2478/v10164-010-0008-8 | Fatigue of Aircraft Structures |
| Dorota Kocańda 1 Volodymyr Hutsaylyuk 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | ANALYSING MICROMECHANISMS OF INITIATION AND PROPAGATION OF SHORT FATIGUE CRACKS FROM RIVET HOLES IN THE ALUMINUMS SHEETS | Researched initiation and propagation of short surfaces fatigue cracks out of open in double-sided botch laminated sheet of aviation aluminum alloy 2024-T3 at stable amplitude one-sided bend (R=0.1). Research of the initial stage of development of cracks is realized by use of a SEM microscope, and it allowed to set the place of origin of crack and mikromechanisms of fracture of aluminum sheets, and also type of front of crack. Established a large enough scatter of velocity of propagation in the area of development of short cracks, which for a sheet from this alloy, with a thickness of 3 mm, reaches 0.5 mm. On the basis of fractografy researches modified model of analytical description of propagation of short fatigue crack is proposed. | brak | 2009 | 1 | 1 | 84-101 | 10.2478/v10164-010-0009-7 | Fatigue of Aircraft Structures |
| Dorota Kocańda 1 Janusz Torzewski 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | DETERMINISTIC APPROACH TO PREDICTING THE FATIGUE CRACK GROWTH IN THE 2024-T3 ALUMINUM ALLOY UNDER VARIABLE AMPLITUDE LOADING | The paper presents the attempt to predict fatigue crack growth rate in a component subjected to variable amplitude loading containing overload-underload cycles. For this goal in a deterministic approach the modified Willenborg retardation model was applied. To provide experimental data the research into fatigue crack growth for 2024-T3 aluminum alloy sheet CCT specimens under LHL type block program loading with multiple overload-underload cycles was developed. The microfractographic analysis of fatigue fractures with the use of the transmission electron microscope (TEM) made it possible to trace the effect of block program loading on the crack growth rate. The knowledge of the affection of a particular overloadunderload cycle or a block of these cycles on crack rate on the basis of microfractographic analysis was utilized for assessing the equivalent loading for the LHL block program. The diagrams that presented the crack growth rate both on the surface and inside the aluminum alloy sheet was performed. The crack growth rate inside the sheet was estimated on the basis of the striation spacing analysis. | aluminum alloy, fatigue crack growth rate, microfractographic analysis, Willenborg retardation model | 2009 | 1 | 1 | 102-115 | 10.2478/v10164-010-0010-1 | Fatigue of Aircraft Structures |
| Dorota Kocańda 1 Janusz Mierzyński 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | THE EFFECT OF A COMPLEX STRESS STATE ON FATIGUE CRACK PROPAGATION AND THE ORIENTATION OF THE CRACKING PLANE IN VT3-1 AERONAUTICAL TITANIUM ALLOY | The subject of the paper is the investigations of fatigue crack imitation and propagation in notched specimens made of the VT3-1 aeronautical russian titanium alloy under combined bending - torsion loading. The presence of short cracks was revealed at various ratios of bending to torsion. Experimental courses of short and long crack growth rates have been proved by the SEM and TEM micrographs which illustrated the changes in the mechanism of cracking in the examined specimens. The attempt was undertaken in order to explain partly brittle fracture that was observed in the range of fatigue short crack growth in the VT3-1 titanium alloy specimens. The results of the study of atmospheric hydrogen absorption capability and its ability for penetration inside the faces of nucleated and propagated microcracks in the surface layer allowed for suggestion that the cleavage mechanism of fracture found in the regime of short crack growth in the VT3-1 titanium alloy specimens was induced by hydrogen. | brak | 2009 | 1 | 1 | 116-130 | 10.2478/v10164-010-0011-0 | Fatigue of Aircraft Structures |
| Andrzej Leski 1 Sławomir Klimaszewski 1 Marcin Kurdelski 1 | 1) Air Force Institute of Technology, Ks. Boleslawa 6 street, 01-494 Warsaw, Poland | THE FATIGUE LIFE ASSESSMENT OF PZL-130 ORLIK STRUCTURES BASED ON HISTORICAL USAGE DATA | Material fatigue is the basic factor limiting aircraft’s durability. It comes from the fact that changing loads affect aircraft structure as well as from the fact that aircraft’s mass restrictions do not allow for diminishing stress to the level when material fatigue does not occur. Estimating fatigue durability of a particular structure as well as its actual fatigue damage degree is possible when the history of loads affecting the structure is known. Accuracy of loads monitoring influences the accuracy of indicated fatigue wear. In case of older structures, which have been maintained according to safe life principle, the number of hours have been commonly used as a fatigue wear indicator. After aircraft structure reaches flying time estimated by the produces, it is considered as fatigue wear and it is no longer in service. In case of a lack of results of loads spectrum measurements, results of tests conducted for other aircraft (of similar structure and assignment) can be used. For this purpose, average loads spectrum has been elaborated for particular aircraft groups, for example, HELIX, FELIX, FALSTAFF, ENSTAFF, TWIST(10). In the case of small aircraft, the data from FAA (2) report have been often used. This article describes the way of fatigue wear estimation for PZL-130 Orlik aircraft on the basis of historical data from flight recorders. | aircraft structure, fatigue, usage profile | 2009 | 1 | 1 | 131-139 | 10.2478/v10164-010-0012-z | Fatigue of Aircraft Structures |
| Antoni Niepokólczycki 1 Andrzej Szot 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | APPLICATION OF FINITE ELEMENT METHOD FOR DETERMINING LOADS FOR THE NEW METHOD OF ACOUSTIC FATIGUE TESTING OF AIRCRAFT STRUCTURES | For aircraft structures the failures due to acoustic fatigue are very important, particularly for new supersonic or short take-off aircraft. The majority of acoustic fatigue life test methods are based on the reproduction of noise acting on the structure – in reverberation chambers or progressive wave tubes. The method described in this paper is based on the reproduction of dynamic response of the structure subjected to random acoustic loading. | brak | 2009 | 1 | 1 | 140-149 | 10.2478/v10164-010-0013-y | Fatigue of Aircraft Structures |
| Mirosław Rodzewicz 1 Wojciech Owczarek 1 | 1) Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland | INVESTIGATIONS INTO GLIDER CHASSIS LOAD SPECTRUM | The paper describes investigations on load spectrum of a glider chassis during take-off and landing. The experiments were conducted on different kinds of airfield surfaces, and recorded time-courses of loads acting on the main and front gear were used for analysis. The paper shortly describes the tests carried out on a PW-6 glider (description of the measurement system installed on the glider main and front landing gear). There is included a comparison of different methods used for time-courses analysis and full cycle counting. The following methods were used: local extremes count method, level exceeds count method, full cycles count method, rainflow count method, and a method developed by the first author. The outputs generated by application of the above mentioned methods for different test-time-courses of load, and the real time-courses of load observed during take-off and landing, are described. Paper presents also load spectrum for the main gear for take-off and landing on a grassy runway. This load spectrum were used later on an experimental stand, build by the authors for fatigue tests of special shock-absorbing element, made from GFRP composite for a new glider. | brak | 2009 | 1 | 1 | 150-169 | 10.2478/v10164-010-0014-x | Fatigue of Aircraft Structures |
| Lucjan Śnieżek 1 | 1) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | EXPERIMENTAL AND THEORETICAL INVESTIGATIONS OF FATIGUE CRACK GROWTH IN D16 ALLOY | In this work the arising and development of fatigue crack in aluminium alloy D16, taking into consideration the influence of notch in the form of hole with incisions which were done on its sides were tested. The process of working out of tests’ programme was preceded by numeric analysis of stresses pattern and strains distribution in the zone of notch’s influence which was focused on determination of stresses’ face values. To examine stress and strain distributions, the specialised FEM software (MSC.Patran and MSC.Nastran) was applied. Findings have been presented in the form of a statement of σmax and εmax values, and functions of the following factors: aσ, aε, and ak, computed on the grounds of these values for both different distances from the bottom of the notch and assumed levels of loading the specimens. Theoretical analysis has been supplemented with experimental investigation into the microstructure of fatigue-fracture surfaces in the area of crack initiation and that of fatigue of a propagating crack. The paper has been intended to present a model of the probabilistic estimation of fatigue life of structural members. The model has been based on the deterministic description of the cracking. Analyzed were components with notches in the form of centrally located holes with side cuts. In the method of probabilistically approaching the crack propagation, some dependences have been used that take account of the presence of areas showing plastic strains in front of crack tips. It has been assumed that the cracking can be modeled on the grounds of some general-purpose quantity used to describe the energy state in the area of the crack tip, i.e. the Rice’s integral (J). The formulated computational model has been used to estimate fatigue life of model components made of D16 alloy. Experimental work was carried out using some flat specimens with centrally positioned holes. They were exposed to flat bending at R = 0. Analytical and experimental results have shown pretty good conformity. | brak | 2009 | 1 | 1 | 170-190 | 10.2478/v10164-010-0015-9 | Fatigue of Aircraft Structures |
| Sebastian Szałkowski 1 Marcin Gębski 1 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland | STATIC AND FATIGUE STRUCTURAL TESTS FOR EADS-CASA | The paper presents structural tests of Airbus aircraft subcomponents which have been carried out at the Institute of Aviation in Warsaw to the order of EADS CASA in Madrid since 2004. Subcomponents of A318 and A400M aircraft were tested. Short descriptions of tested specimens, test set-up and test methods are included. | brak | 2009 | 1 | 1 | 191-193 | 10.2478/v10164-010-0016-8 | Fatigue of Aircraft Structures |
| Lucjan Witek 1 | 1) Rzeszów University of Technology, al. Powstańców Warszawy 12, 35-029 Rzeszów, Poland | EXPERIMENTAL CRACK PROPAGATION ANALYSIS OF THE COMPRESSOR BLADES WORKING IN HIGH CYCLE FATIGUE CONDITION | This paper presents results of experimental vibration tests of the helicopter turbo-engine compressor blades. The blades used in investigation were retired from maintenance under technical inspection of engine. Investigations were conducted for selected undamaged blades, without existence of preliminary cracks or corrosion pits. The blades during experiment were entered into transverse vibration. The crack propagation process was conducted in resonance condition. During the fatigue test, the growth of crack was monitored. In the second part of work, a nonlinear finite element method was utilized to determine the stress state of the blade during vibration. In this analysis a first mode of transverse vibration were considered. High maximum principal stress zone was found at the region of blade where the crack occurred. | Compressor blade; Failure analysis; Crack propagation; Vibration; FEM | 2009 | 1 | 1 | 195-204 | 10.2478/v10164-010-0017-7 | Fatigue of Aircraft Structures |
| Lucjan Witek 1 Daniel Musili Ngii 1 Tadeusz Kowalski 1 | 1) Rzeszów University of Technology, al. Powstańców Warszawy 12, 35-029 Rzeszów, Poland | THERMAL FATIGUE PROBLEMS OF TURBINE CASING | This paper presents numerical stress analysis of the turbine casing of an aero-engine. To solve the problem, the geometrically complicated numerical model was created. The finite element method was used in computations. In results of nonlinear static analyses performed for both mechanical and thermal load occurred under operating condition of engine, the stress and deformation contours were generated. High thermal stress gradients were found at the region of casing where fatigue cracks were detected during engine operation. | brak | 2009 | 1 | 1 | 205-211 | 10.2478/v10164-010-0018-6 | Fatigue of Aircraft Structures |
| Jerzy Kaniowski 1 Wojciech Wronicz 1 Jerzy Jachimowicz 2 | 1) Institute of Aviation, Materials and Structures Research Center, Al. Krakowska 110/114, 02-256 Warsaw, Poland 2) Military University of Technology, Faculty of Mechanical Engineering, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland | Methods for Global and Local FEM Analysis of Riveted Joint on the Example of the PZL M28 Skytruck Aircraft | The paper considers some aspects of FEM modeling of riveted joints with application of shell elements and submodeling technique. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints. The project assumed FEM modeling of the operating aircraft’s structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various rivet models were presented and usefulness of them was discussed. Influence of the following simplification was analyzed; • neglecting of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglecting of contact phenomenon • neglecting of secondary bending. The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analyzed as well. In the second part, the example of analysis of riveted joint on a lower skin of the PZL M28 Skytruck aircraft wing was presented. A submodeling technique was used there. At first, part of the wing model, was built. It includes 7 ribs and 6 bulkheads between them. Boundary conditions were taken on a basis of operation data. Presence of rivets was neglected. The Linear material model was used. The purpose of this calculation was to gain accurate boundary conditions for the model of riveted joint on the middle rib. Next a shell model of chosen area was build. Boundary conditions were set on a basis of result from previous analysis. Because of large stiffness difference between part models (part of wing and riveted joint) forces, instead of displacements, were used, as boundary conditions. The nonlinear model of material was used. A contact effect, secondary bending and residual stresses were taken into account. Results from this analysis are planned to be used as boundary conditions in a calculation of single rivet with solid detailed model. The presented method allows analyzing phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN and NASTRAN software. | 2009 | 1 | 1 | 212-225 | 10.2478/v10164-010-0019-5 | Fatigue of Aircraft Structures |