Temperature Measurements of Both Sliding Surfaces and Estimation of Temperature Profile across Film Thickness under EHL Conditions

This paper describes an experimental study of temperature measurements of both sliding surfaces and estimation of film temperature profile across film thickness under point EHL conditions. The surface temperature and the average film temperature between a steel ball and a sapphire disk were measured by an improved infrared technique. The temperature of the sapphire disk was measured with use of the disk sputterd Cr layer to intercept the radiation from the ball surface and to detect the infrared radiation from only the layer. The temperate profile across the film thickness less than 1 μm was estimated by assuming it to be a parabolic curve. The results show that the temperature of slower surface is higher than that of the faster surface as the velocity difference increases, and that the temperature gradient across film thickness also exists at the inlet region because the heat generated at the contact region is transferred back from the slower surface to this region. Therefore, the effect of viscosity wedge caused by the temperature gradient occurs at the inlet region. The effect of viscosity wedge seems to influence the formation of the film thickness in the conditions.