Evaluation on Distribution of Fatigue Life with Crack Initiation and Propagation Based on Probability Theory

It is very important for the damage tolerance design of a structure to reveal the behavior of fatigue cracks of the used material. They have some uncertainties, the random applied loads or the residual strength caused by manufacturing process and so on. It is difficult to evaluate the behaviors of real fatigue cracks. In this paper, an evaluation method for fatigue life based on fatigue crack length has been proposed. Fokker-Planck equation, which can describe fatigue crack propagation under random load and random propagation resistance, has been proposed. The distribution of fatigue life has been analyzed by combining both of the distribution of crack initiation life and the distribution of propagation life.