Assessment of Fatigue Behavior and Effects of Crack Growth in Aluminium Alloys 6082 under Various Stress Ratios

The purpose of this study is to investigate the fatigue behaviour of the aluminium alloy 6082 by a finite element analysis (FEA). The tests are released for various specimens subjected to cyclic tensile loading in order to characterize the damage evolution and the fatigue strength of the aluminium alloy 6082. The results show the Wöhler curves (S-N curves) for the tested specimens under various stress amplitude levels and for different stress ratios values (R=0, R=0.5, R=-1). The obtained data highlights the strong influences of the stress ratios R and the effects of high cyclic loading on the decreasing of aluminium alloys 6082 life and performances. Afterward, fatigue crack growth under tensile loading was investigated, in this way fatigue tests have been performed on specimens with different pre-cracks sizes to underline the influences of the crack growth on the lifetime and fatigue behaviour of the tested specimens. The predicted fatigue life and the results obtained for the different loading conditions presented in this study were found to be in good agreement with the experimental fatigue investigations published in the literature

Fatigue Behavior And Damage Modeling Of Train Wheels In Different Cases Of Loading

Abstract: The goal of this study is to highlight the various stress and strain states responsible for degradations of the couple wheel/rail, so the model is applied in three cases of loading, order to compare the results obtained for the three cases and the numerical method applied in this study is that of the finite elements to obtain the form of nodal solution in a very detailed way in the zones which are the seat of stress concentration, deformations and displacements, the results of this study also make it possible to define a strategy of maintenance. The study also shows the fatigue of the wheel, characterized by the lifespan, the safety coefficient and result of damage

Damage detection and location in woven fabric CFRP laminate panels

The need for multifunctional carbon fibre composite laminates has emerged to improve the reliability and safety of carbon fibre composite components and decrease costs. The development of an electrical selfsensing system for woven fabric carbon fibre composite laminate panels which can detect and locate damage due to impact events is presented. The electrical sensing system uses a four probe electrical resistance method. Two different sensing mats are investigated, the main difference between them are the surface area of the electrodes and the distance between the electrodes. To investigate the damage sensitivity of the sensing system for woven fabric carbon fibre composite laminate panels, panels are produced with various thicknesses from 0.84 to 3.5 mm and are impacted at energies from 1 to 10 J to generate barely visible impact damage. Damage is detected using global electrical resistance changes, the changes in electrical resistance vary depending on carbon fibre volume fraction, spacing distance between the sensing electrodes in the sensing mats, the surface area of the electrodes, damage size, and damage type; it is found that the thicker the panel, the less sensitive the electrical resistance system is. The effect of the surface area of the sensing electrodes is high on the electrical resistance baseline, where the baseline increases by up to 55% when the surface area of the sensing electrodes increases from 100 mm2 to 400 mm2; while spacing distance between electrodes has a greater effect on damage sensitivity of the electrical resistance sensing system than the surface area of the sensing electrodes

Evaluation des mécanismes d'endommagement dans les stratifiés verre/époxy par émission acoustique

International audienceThis present work is devoted to the evaluation and identification by acoustic emission of the damage mechanisms in glass/epoxy composite laminates. The tested specimens were subjected to static and cyclic tensile stress in order to follow the propagation of the various modes of damage over time and to detect the most critical ones leading to the total rupture of the tested samples. Damage is manifested by matrix cracking, inter-ply debonding, delamination and fiber breakage. The acoustic signals collected during the experimental tests were analysed by a classification method consisting of the k-means method and principal component analysis (PCA)Le présent travail est consacré à l’évaluation et l’identification par émission acoustique des mécanismes d’endommagement dans les stratifiés verre/époxy. Les éprouvettes ont été sollicitées en traction statique et cyclique afin de suivre les différents modes d’endommagement dans le temps et de détecter ceux les plus critiques conduisant à la rupture totale des échantillons. L’endommagement se manifeste par la fissuration matricielle, la décohésion inter-plis, le délaminage et la rupture des fibres. Les signaux acoustiques collectés au cours des essais ont été analysés par une méthode de classification composée de la méthode de k-moyennes et d’une analyse en composantes principales (ACP)