A new methodology for predicting crack initiation life was presented and validated experimentally. The methodology considered that the total fatigue life was the summation of crack initiation life and crack propagation life, since fatigue failures were due to crack initiation and crack propagation. It was established that the crack propagation life could be estimated, based upon a modified Paris law when the size of the crack was greater than a certain value. However, there was no verified method for estimating the crack initiation life with good accuracy. The proposed methodology for predicting the crack initiation life was based upon a dislocation model, and the constants for the model were determined by the crack initiation lives obtained by a new approach. This new approach determined the crack initiation life by subtracting the predicted crack propagation life from the experimentally obtained total fatigue life. The developed crack initiation life model was combined with a crack propagation life model for the prediction of fatigue life. It was noted that the standard deviation in the ratios of experimental life to predicted life by the developed fatigue life model was only 14% of that given by the international standard.

A New Methodology for Predicting Crack Initiation Life for Rolling Contact Fatigue Based on Dislocation and Crack Propagation. C.R.Liu, Y.Choi: International Journal of Mechanical Sciences, 2008, 50[2], 117-23