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 (hg/hff) can be predicted using the base oil viscosity (η), 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 zr and surface tension σ. A universal power-law relationship between the relative film thickness in a deep groove ball bearing and the nondimensional number (ηbu)/(zrσ) for all loading and grease lubrication conditions is presented for use in predicting film thickness.