Simulating angular ball bearing lubricated elliptical contacts Film thickness and traction measurements

A high performance barrel and plate apparatus was built to study film formation and traction by simulating the real situation of a lubricated elliptical contact in an angular ball bearing under general kinematic conditions. Simultaneous measurements of load, speed of each surface, traction, and film thickness by optical interferometry can be performed. The sapphire disc plate and the steel barrel are driven independently at constant controlled speeds. Small relative sliding, lateral sliding and spinning near pure rolling conditions can be imposed by controlling barrel shaft angle contact location. Tests were performed at ambient temperature for a small barrel whose principal radii are 1.34 mm and 9.7 mm, for applied loads which generate Hertzian pressures up to 2 × 10⁹ N/m², and for a low viscosity mineral oil. Typical experimental results show that under elasto-hydrodynamic conditions, the centre film thickness is slightly below the values calculated from classical elastohydrodynamic theories and that oil starvation occurs at high speeds. Traction curves versus slide/roll ratio are presented for different loads and under spinning and lateral sliding conditions.