Probabilistic fatigue life prediction using an equivalent initial flaw size distribution

A new methodology is proposed in this paper to calculate the equivalent initial flaw size (EIFS) distribution. The proposed methodology is based on the Kitagawa-Takahashi diagram. Unlike the commonly used back-extrapolation method for EIFS calculation, the proposed methodology is independent of applied load level and only uses fatigue limit and fatigue crack threshold stress intensity factor. The advantage of the proposed EIFS concept is that it is very efficient in calculating the statistics of EIFS. The developed EIFS methodology is combined with probabilistic crack growth analysis to predict the fatigue life of smooth specimens. Model predictions are compared with experimental observations for various metallic materials.