Study on the Correlation between the Grease Film Thickness and Fatigue Life of Bearings

The film thickness and bearing fatigue life of lubricating grease with different consistencies, base oil viscosities and base oil types were tested by the oil film thickness measuring instrument and bearing life strengthening testing machine, and the correlation between them was established. The results show that higher consistency of the lubricating grease corresponds to increased effective viscosity in the contact zone, leading to a thicker grease film. For the same kind of base oil, the greater the viscosity is, the greater the film thickness is. The viscosity-pressure coefficient of PAO oil, ester oil, and mineral oil with the same viscosity increases successively, resulting in a progressive increase in the thickness of the grease film when utilizing PAO oil, ester oil, and mineral oil as base oils. The worse the film forming capacity of lubricating grease, the shorter the fatigue life of bearing. The relationship between fatigue life and film thickness can be described as an exponential function. This study provides a theoretical basis for optimizing the performance of lubricating greases and their selection for bearing applications. The established correlation model between film thickness and fatigue life offers significant engineering guidance for the reliability assessment and service life prediction of industrial bearing systems. Furthermore, it provides new insights and directions for future research in related fields.