Experimental investigation of effects of slip ratio on elastohydrodynamic lubrication film related to temperature distribution in oil films

This article describes the mechanism of variations of elastohydrodynamic lubricated oil film under high slip ratio conditions. Experiments were conducted using a ball-on-disc apparatus. The thickness of the oil film was measured by optical interferometry. Temperature increase in the ball surface, disc surface, and oil film was determined by an improved infrared technique using a transparent disc without any coating and non-transparent disc with a comparatively thick Cr coating. The results reveal that the film thickness decreases with an increase in the slip ratio at constant entrainment velocities. The shape of the oil film indicates an increase in the thickness gradient at the inlet region and a slight increase in the oil film just behind the exit region. The temperature at the inlet region increases with the slip ratio and entrainment speed. Both the inlet region and the contact area exhibit a significant temperature difference between the surfaces. The variation of the shape of the oil film can be explained on the basis of the viscosity wedge action. The viscosity wedge action, heating at the inlet region, and inflow of heat from a slower surface to the inlet region reduce the film thickness considerably.