Film thickness decay and replenishment in point contact lubricated with different greases: A study into oil bleeding and the evolution of lubricant reservoir

Six different types of greases were tested on the ball-on-disc test rig under starved condition. Both the central film thickness and the cross section film thickness profile were analyzed to better understand the mechanism of grease starvation. In-situ Monitoring of lubricant reservoir was achieved by using a high-resolution camera. Results showed that a new reservoir would re-form after a period of operation after the contact lost its initial grease reservoir under starved condition. The higher oil bleeding ratio of grease, the larger re-formed lubricant reservoir would be. A turning point on the central film thickness curve was found, which was due to the loss and re-formation of the lubricant reservoir.