Influence of grease rheology on thrust ball bearings friction torque

The friction torque and the operating temperatures in a thrust ball bearing were measured for seven different types of greases, including three biodegradable greases having low toxicity. These friction torque tests were performed using a modified Four-Ball machine.Rheological evaluations of the lubricating greases were made using a rheometer. Bleed oils were extracted from the greases and the dynamic viscosities were measured.In order to compare the performance of the lubricant greases in terms of friction, the grease characteristics were related to experimental results, showing that the interaction between thickener and base oil have strong influences in the bearing friction torque.

► Loss moduli vs. consistency index shows a linear relationship for different grease thickeners.
► Bleed oil viscosity of greases can be different from the corresponding base oil viscosity.
► Thrust bearing rolling torque mainly depends on the bleed oil viscosity and replenishment factor.
► Thrust bearing sliding torque mainly depends on the specific film thickness and bleed oil nature.