P-S-N / P-F-L CURVE APPROACH USING 3-PARAMETER WEIBULL DISTRIBUTION FOR LIFE AND FATIGUE ANALYSIS OF STRUCTURAL AND ROLLING CONTACT COMPONENT

摘要

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 account of the probabilistic approach of dealing with stress or force life for only median life. Therefore, a new approach to life estimation and fatigue limit concept is proposed by using three-parameter Weibuil distribution consisting of a minimum life as the third parameter with a normalized constant Weibuil slope m. The values of m obtained in the previous paper from life tests for bearing steel were m = 1.3 to m = 1.8. In this paper m = 1.5, a constant mean value is used for the analysis and independent of the life distributions of any given experimental stress levels. It is made clear that the stress or load life exponent of 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 Weibuil slope.