On the Assessment of Mechanical Degradation of Grease Using Entropy Generation Rate

Abstract

A methodology for continuous monitoring of grease degradation subjected to mechanical shearing is proposed. It is hypothesized that the mechanical degradation of grease is akin to the running-in process in a tribo-pair with both transient and steady-state regimes. To validate the hypothesis, a series of mechanical shearing tests are performed on three grades of grease: NLGI 00, NLGI 1, and NLGI 2.5 by employing a rheometer. From the results, a more effective method using the entropy generation rate is proposed for continuous monitoring of grease degradation. The proposed method is extended to estimate the time for a grease subjected to mechanical shearing to degrade to a lower grade. The efficacy of this method is demonstrated via long duration testing in a custom-built ball-bearing test apparatus.