Influence of Fatigue Damage in Dynamic Tensile Properties of AISI 4140T Steel

Usually material properties are determined from damage free materials, but is unknown if these properties can vary with respect to 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 deep understanding of the dynamic behavior of materials and components. In this work experimental results are presented in the static and dynamic behavior of steel with fatigue damage and subject to impact loading. Samples subjected to previous high and low cycle fatigue are considered. The material used is AISI 4140T steel, this material is used in several engineering applications and they present different mechanical behavior. Fatigue damage was introduced on the specimens at levels of 25%, 50% and 75% of the fatigue life. Once the fatigue damage was generated, the specimens were tested on a Hopkinson bar test apparatus modified to tension loading condition. The results show how the previous fatigue damage can modify the mechanical properties of the material tested, as the yield stress, ultimate stress, elongation percentage and reduction of area percentage.