Weibull Distribution of Rolling Contact Fatigue Life and Deviations Therefrom

Abstract

A composite sample of over 2500 rolling element bearing fatigue failures is examined for fit of the standardised lives to a Weibull distribution with zero lower bound. Good fit is confirmed in the most used cumulative failure probability region between 10% and 60%. Outside this region, experimental life is larger than the Weibull prediction. A short but finite minimum life appears to exist. The excess of experimental over Weibull life is analysed by evaluating the mathematical conditions assuring validity of a Weibull representation. The inapplicability of asymptotic theory to late failures is suggested. A two-phase fatigue mechanism of crack initiation and propagation is outlined which serves to explain excess life in the early failure region. Data presented can be used to improve the accuracy of life estimates in the early failure region.