Temperature measurements of oil film and surface in point contact EHL under high slip ratio conditions

This paper describes an experimental study on the viscosity wedge effect in point contact EHL under high slip ratio condition. In order to discuss the effect, the temperature rises on the ball surface and in the oil film as well as the film thickness were measured with a ball-on-disk apparatus. Both the temperature measurements were conducted by an improved infrared technique with two kinds of optical band pass filters. The film thickness measurement employed the two color optical interferometry technique. Experimental results indicate that the oil film was formed under the steady state condition in spite of no entertainment velocity and a specific conical surface depression was found in the Hertzian contact area. The film thickness in the depression was sensitive to the slip ratio, the sliding speed and the load. The temperature increases markedly in the depression. As a conclusion, these results appear to be caused by the effect of viscosity wedge.