The lubrication mechanism behind the transition from churning to bleeding in grease lubricated bearings-Experimental characterization

Grease lubrication mechanism can be divided into two distinct phases: the churning phase and the bleeding phase. Grease churning starts when the bearing operation starts, and bleeding commences at the end of churning. During the churning phase, the friction torque and the bearing/grease temperature are very high. At the end of churning, the temperature drops to a steady state. The transition from churning to bleeding is not well estab-lished. In this investigation, we performed bearing experiments and rheological studies to understand the transition phenomenon. The results show that the churning-to-bleeding transition ends when grease becomes uniform in the bearing. We also present an experimental method based on degradation and rheology to identify the churning behavior type.