Influence of Contact Pressure on Central and Minimum Film Thickness Within Ultrathin Film Lubricated Contacts

Recent numerical results have indicated that the relationship between the film thickness and the speed may not always follow the simple power law, especially under severe conditions. This paper is aimed at obtaining experimental results at high contact stresses and low speeds to study the thin film behavior. Ultrathin lubricant films were observed at maximum Hertz pressures of 0.52, 1.01, and 1.54 GPa by using an optical test rig. Central and minimum film thickness values were obtained with thin film colorimetric interferometry from chromatic interferograms. The nonlinear behavior of both central and minimum film thicknesses in log-log coordinates was observed as rolling speed and thereby film thickness decreased. This tendency became more obvious at higher contact pressures.