An engineering model to estimate consistency reduction of lubricating grease subjected to mechanical degradation under shear

• A model for prediction of grease life subjected to mechanical degradation is presented.
• Predictions are validated experimentally for three different greases.
• Illustrative examples are presented to demonstrate the application of the model.

A model is presented that uses the principles of irreversible thermodynamics to predict the reduction in consistency of a lubricating grease undergoing mechanical shearing action. Here we restrict our attention to operating temperatures far below the initial activation energy needed to initiate chemical degradation or base oil evaporation. Thus, mechanical degradation is the dominant degradation process. The predictions of the model are validated using the experimental results obtained by testing three greases subjected to different shear rates and temperatures. Illustrative examples are presented to demonstrate the application of the model.