Fatigue Limit Concept and Life Prediction Model for Rolling Contact Machine Elements

The weakness of the present method of fatigue limit assessment is discussed and a new approach to fatigue limit assessment using a three-parameter log-log and Weibull plot is proposed. With this new approach to the analysis of alternating fatigue test data, it is confirmed that hearing steel does not show any fatigue limit, whereas structural steel does have a distinct fatigue limit. In absence of a fatigue limit for hearing steel, a minimum life or a minimum number of stress cycles prior to failure is proposed for the analysis of fatigue life behavior under a given rolling contact fatigue load or stress, leading to a three-parameter Weibull life distribution function. The experimental data is found to fit very well to this distribution. A comparison of the stress-life exponents estimated for the structural steel and bearing steel using three methods of analysis shows the values to be very close indicating similarity in their fatigue behaviors.