PhD Defence Min Gao | Film thickness in grease lubricated cylindrical roller bearings

Film thickness in grease lubricated cylindrical roller bearings

Min Gao is a PhD student in the Department of Surface Technology and Tribology. (Co)Promotors are prof.dr.ir. P.M. Lugt and dr. J.A. Osara from the Faculty of Engineering Technology.

Grease film formation in cylindrical roller bearings (CRBs) is not well understood, as most studies focus on ball bearings. This work presents the investigation on single line contact and direct film thickness measurements in grease-lubricated CRBs after churning, using the electrical capacitance method. We measure the film thickness at the highest loaded position and around the circumference. With increasing speed the film becomes more stable, and at the highest loaded position it reaches about 50-70% of the fully flooded prediction based on base-oil viscosity. Circumferential measurements show a minimum film near the transition from the unloaded to loaded zone, indicating a critical lubrication region. Tests with two greases under varying speeds, loads, and temperatures reveal grease-dependent trends. The results provide a measurement-based view of grease EHL behavior in CRBs and highlight effects that future prediction models should include.