Surface Roughness Effects on Fatigue in Partial EHD Lubrication

A simple surface originated fatigue theory has been developed to study the effects of surface topography on the fatigue life of rolling element bearings. The bearing surface fatigue life is assumed to relate to the magnitude of the average shearing stresses generated at the interacting asperities on the surfaces that are separated by an elastohydrodynamic lubricant film of some thickness. Utilizing a published rough surface model, it is possible to express the relative fatigue life of a bearing as a function of the lubricant film thickness to roughness ratio h/σ and a roughness parameter R. Comparison of the theory to sets of published endurance test data has been carried out. Possibilities of fatigue life prediction of both roller and ball bearings in the partial elastohydrodynamic lubrication regime are discussed.