Dynamic tensile behavior of materials with previous fatigue damage

In different engineering applications such as automobile and train crashes, the high speed impact of debris as well as the high speed manufacturing processes, makes it necessary to have a deep understanding of the dynamic behavior of materials and components. There are different experimental techniques to determine the constitutive material behavior. Several constitutive models have been proposed to predict the dynamic response of engineering structures. However, in all cases, initial damage-free material is assumed and the structures are without fatigue damage when tested. The dynamic response of fatigue damaged steel and aluminum specimens subjected to impact loading are investigated in this work. Samples subjected to previous high cycle fatigue are considered. Results show that previous fatigue damage affects the quasi-static behavior of steel more significantly than that of aluminum. Dynamic yield stress of 6061-T6 aluminum samples shows it to be more sensitive to fatigue damage than to strain rate. Previous fatigue damage has a detrimental effect on ductility of 4140T steel, principally under dynamic loading.