Replenishment of the EHL contacts in a grease lubricated ball bearing

Abstract

The film thickness in grease lubricated bearings is usually calculated by assuming fully flooded conditions, using the base oil properties. This paper shows that, for sealed-for-life bearings, starvation already occurs at relatively low speeds, where the film thickness could be described by the product of speed, viscosity and Hertzian semi-contact width. It is shown that replenishment is not significant on the tracks in-between the balls but that it is a local phenomenon. The relation between film thickness and the product of speed, viscosity and contact size is different from what is found in single contacts. The film thickness decreases as a function of speed and viscosity, but the effect is only small leading to an almost constant film thickness with increasing product of viscosity and speed.