BEHAVIOR OF MATERIALS SUBJECTED TO AN IMPACT FORCE AND NEW EVALUATIONMETHOD FOR IMPACT STRENGTH

The size dependence of the amplitude of a stress pulse produced in a r od subjected to an impact force is theoretically considered. Impact fa tigue experiments were performed to see the size dependence of the str ength of structural materials. According to these results, impact fati gue life of a short specimen was shorter than that of a long one. Base d on these considerations, it is shown that the superposition of stres s waves with reversed phase is effective to improve the impact fatigue life. In addition, a new method is proposed to evaluate the impact st rength of materials with stress unit. By this method, influences of st rain rate on the impact tensile strength I(m,t) and impact bending str ength I(m,b) are investigated for carbon steel, aluminum alloy and PMM A using their dynamic stress strain relations which are measured direc tly on each specimen.