Grease film evolution in rolling elastohydrodynamic lubrication contacts

Xinming Li,Gerhard Poll,Ping Yang,Feng Guo,Yang Fei

doi:10.1007/s40544-020-0381-4

Xinming Li, Gerhard Poll + Show 3 more

Open Access

https://doi.org/10.1007/s40544-020-0381-4

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Abstract

Although most rolling element bearings are grease lubricated, the underlying mechanisms of grease lubrication has not been fully explored. This study investigates grease film evolution with glass disc revolutions in rolling elastohydrodynamic lubrication (EHL) contacts. The evolution patterns of the grease films were highly related to the speed ranges and grease structures. The transference of thickener lumps, film thickness decay induced by starvation, and residual layer were recognized. The formation of an equilibrium film determined by the balance of lubricant loss and replenishment was analyzed. The primary mechanisms that dominate grease film formation in different lubricated contacts were clarified.

Highlights

As a primary method for rolling element bearing lubrication, grease lubrication has been extensively studied both on model test apparatus and on a full bearing testing bench [1, 2]
Film thickness measurements were performed with both greases and the corresponding base oil
Over the entire range of disc revolutions, the grease film thickness exceeds that of the base oil

Summary

Introduction

As a primary method for rolling element bearing lubrication, grease lubrication has been extensively studied both on model test apparatus and on a full bearing testing bench [1, 2]. Under constant speed with single charge, the film thickness initially exceeds that of the corresponding base oil and rapidly decreases to below that of the base oil level, mainly due to the progressive starvation in combination with continuous shear degradation [12,13,14,15, 20] Such an evolution pattern over time or disc revolutions was recognized by different testing methods, such as electrical capacitance [25], magnetic reluctance [26], and optical interferometry [12,13,14,15, 20, 27]. The changes in the rheological properties of the inlet grease largely govern the behavior of the elastohydrodynamic lubrication (EHL) films

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