Study of Lubrication Film Formation in Ball Bearings Under Starved Conditions

Abstract

Rolling elements (e.g. rolling bearings, gears, cams and followers, etc.) fall into the most frequently used and highly loaded machine parts in machinery industry. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The entrainment velocity and the lubricant viscosity have the main effect on the film thickness formation in the classic fluid film lubrication. In some engineering applications e.g. grease lubricated rolling bearings, the available lubricant is not enough to fill the gap between the two contact surfaces thereby a poor lubrication conditions occur. Insufficient supply of lubricant may result in starvation and consequently in lubrication film collapse. With decreasing amounts of lubricant, the inlet meniscus approaches the contact entrance and finally causes lubrication film breakdown because of contact starvation. This paper is focused on the study of effect of starved lubrication conditions on lubrication film formation of non-conformal contacts operated under pure rolling conditions. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation in the thrust ball bearing. Nevertheless to start this research the first experiments will be performed using ball on disc optical test rig where EHL contact is realized only between one ball and disc.