Abstract:

Based on the analysis of local stress and strain at the notch root of specimen subjected to repeated impact load, and by applying Coffins strain fatigue formula and taking account of the effect of strain rate, a new formula for predicting the repeated impact fatigue crack initiation life from the tensile properties of 0. 4C-CrNiMoSi steel is developed.By checking with the authors'test results, the formula developed is applicable well to different conditions including some kinds of heat treatment, stress concentration factor and impact energy. And the developed formula can be applied to other steels during the selection of the corresponding fatigue parameter C（fatigue ductility exponent in Collins strain fatigue formula）.

Key words: repeated impact fatigue, crack initiation life, austempering