The effect of asperity interaction on scoring in the rolling-sliding contact of two rollers. Changes in tribological parameters at every load step.

Abstract

From the point of view that scoring is a kind of transition process from a fairly lubricated condition to catastrophic adhesion, changes in tribological parameters such as the friction coefficient, the surface temperature, and the state of oil film formation, at every load step, were reinvestigated from previous test results of scoring conducted with a step-load condition using a two-disk machine. The relation between the surface temperature T and the coefficient of friction f varied with the conditions of asperity interaction, which were controlled by the direction of lay, the roughness heights, and the running-in process. The improvement of conformity between the microgeometries of the two surfaces made the T-f relation similar to that of smooth surfaces. The change of friction coefficient corresponded to the state of oil film formation. In the case of a hunting drive ratio of 1.95, when the T-f relation showed thermally unstable changes, that is, a simultaneous increase in the surface temperature and the friction coefficient just before the end of the load step, scoring did not always occur. Sometimes the scoring limits were higher than when using an integral drive ratio of 2, though no significant difference was observed in their T-f relations .These facts suggest that there is a difference in the probability of transition to scoring by the drive ratio.