Behaviour of materials subjected to an impact force and new evaluation method for impact strength

Abstract

The size dependence of the amplitude of a stress pulse produced in a rod subjected to an impact force is theoretically considered. Impact fatigue experiments were performed to see the size dependence of the strength of structural materials. According to these results, impact fatigue life of a short specimen was shorter than that of a long one. Based on these considerations, it is shown that the superposition of stress waves with reversed phase is effective to improve the impact fatigue life. In addition, a new method is proposed to evaluate the impact strength of materials with stress unit. By this method, influences of strain rate on the impact tensile strength Im,t and impact bending strength Im,b are investigated for carbon steel, aluminium alloy and PMMA using their dynamic stress strain relations which are measured directly on each specimen.