A Contact Stress Model for Predicting Rolling Contact Fatigue

Predicting fatigue performance in concentrated contacts under thin film (or mixed) lubrication conditions has historically involved various empirical approaches. Typically a lubrication parameter is used in an experimentally derived equation to predict the expected rolling contact performance. However, this model doesn't explain the performance improvements. Enhanced finish bearings have exhibited longer life than standard finish bearings, especially when bearings are operated with thin EHL film. In this paper, the contact surfaces of test bearings were analyzed by using a micro-macro contact model in which the macro-contact was elastic contact, and the micro-contact was elastic-plastic contact. The interior subsurface stress maps were calculated from the real contact surfaces, which included the effects of roughnesses, waviness, and profiles. The predicted subsurface stress maps statistically explored the local stress levels under the real contact surfaces for various EHL film thicknesses, and show the reason why the enhanced finish bearings have longer life than the standard finish bearings with thin EHL film operating conditions.