Adaptation of a flywhell to aluminium alloy for studying the influence of a fatigue predamage on its dynamic plasticity

Abstract
Through this study, we try to characterize fatigue loading influence on dynamic response of an aluminium alloy, a 2017A T3. In fact, if many works consist to describe the fatigue behaviour or the impact behaviour of materials, few ones concern effects of combined loadings. Tensile-compression loadings are performed for fatigue with an Amsler vibrophore whereas the impact is realized through tensile loading with a flywheel. To fatigue predamage, stress levels are chosen in the high cycle fatigue area and several configurations (i.e : stress level / fracture probability) have been performed. To carry out impact tests, first it is necessary to adapt the impact testing machine in order to test metallic materials and to obtain data directly exploitable for the derivation of the intrinsic material behaviour. Actually, dynamical perturbations induced by the high velocity loading have to be eliminated to observe material behaviour. This is made by the way of mechanical modifications of the specimen holding device and by a numerical processing of the load sensor signal ; the system is validated to 5 ms^-1 loading speed. Then, particular behaviours for combined loadings appear for residual macroscopic constitutive equations : weakened behaviour, no predamage influence and strenghtened behaviour.