Micro-geometry lubrication and life ratings of rolling bearings

Abstract

Following the pioneer work of Ertel-Grubin and Dowson and Higgingson, the field of elastohydrodynamic lubrication (EHL) has witnessed a remarkable increase in new developments, notably the incorporation into the analysis of roughness and other surface features (micro-EHL). This article describes the application of new developments in micro-EHL in the deduction of simple analytical formulations that might describe, in a better way, the lubrication of rolling bearings and the effects on life ratings. In this context the lubrication quality factors κ (used in rolling bearing technology) and Λ (generally applied in machine design) are critically compared and discussed. It is found that the commonly used average roughness, R q, is not quite able to properly account for the surface topography effect when the detailed micro-EHL response of the surface has to be accounted for. To this effect, the whole surface micro-geometry needs to be retained in the evaluation. A calculation methodology suitable for this type of analysis is proposed and used in a parametric evaluation of standard bearing surfaces.