Film Thickness in Grease-Lubricated Deep Groove Ball Bearings — A Master Curve

Film thickness in a grease-lubricated bearing is a critical bearing operation parameter, yet there are no models available to predict it. Our recent articles demonstrated that the relative film thickness ((Formula presented.)) can be predicted using the base oil viscosity ((Formula presented.)), half contact width (b), and linear speed (u) for any axially loaded deep groove ball bearing. In this article, we extend this study to include radial loads and combined—axial and radial—loads. Radial load application causes an additional replenishment in the unloaded zone, introducing a new length variable (Formula presented.) and surface tension (Formula presented.) A universal power-law relationship between the relative film thickness in a deep groove ball bearing and the nondimensional number (Formula presented.) for all loading and grease lubrication conditions is presented for use in predicting film thickness.