P-S-N/P-F-L curve approach using three-parameter Weibull distribution for life and fatigue analysis of structural and rolling contact components

In almost all cases of the estimation of fatigue limit for structural materials and bearing steels, the practice of using S-N curves obtained by plotting the applied stress against the number of stress cycles has been continuing to date. It usually takes into account the probabilistic approach of dealing with the stress or force life,for only median life. Therefore, a new approach to life estimation and the fatigue limit concept is proposed by using a three-parameter Weibull distribution consisting of a minimum life as the third parameter with a normalized constant Weibull slope m (Shimizu (4)). The values of m obtained in the previous paper from life tests for bearing steel were found to be in the range of m = 13 to 1.8. In this article, a constant mean value, (m) over bar = 1.5, is used for the analysis and is considered to be independent of the life distributions for any given experimental stress levels. It is made clear that the stress or load life exponent of the P-S-N/P-F-L (probabilistic stress/force life) curve has a constant value for any probability of failures and that it depends on the Weibull slope.