There are many mechanical factors which affect fatigue strength of materials. However, studies on the influence of strain rate on impact loading are not enough. In addition, when fatigue fracture causes in a machine or a structure, its initiation points at the shape changing part. From the viewpoint of these, our purpose is to experimentally clarify how the strain rate and shape changing portion affect the material strength. As a result, we derived empirical formulas on impact loading of SS400 steal and clarified their coefficients.
