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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 ( h g / h ff ) 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 z r and surface tension σ. A universal power-law relationship between the relative film thickness in a deep groove ball bearing and the nondimensional number (η bu) / ( z r σ) for all loading and grease lubrication conditions is presented for use in predicting film thickness. [ABSTRACT FROM AUTHOR]

Mechanical degradation by shear is one of the mechanisms that limits the life-time of lubricating grease in a rolling bearing. It results in a change of the micro-structure of the thickener–oil system, leading to a change in bleed and consistency. The resistance to degradation can be quantified using a grease worker. In this article, a novel approach is described, where the grease worker is used to measure the rheological properties of a grease in situ, while aging the grease. Mechanical energy and pressure losses are calculated using the measured force that is required to push the plate with holes through the grease in the cylinder of the grease worker. A pipe flow model in combination with a power law rheology model are used to analytically determine the power law fluid consistency index and exponent while aging the grease. The model validity is verified using computational fluid dynamics simulations and measurements using a rheometer with plate–plate geometry. [ABSTRACT FROM AUTHOR]