Effect of surface roughness on mixed EHD lubrication characteristics

摘要

The effect of surface roughness on the mixed EHD lubrication characteristics has been studied in this paper by using a numerical approach developed recently by Zhu and Hu (1), (2). This approach is capable of handling measured rough surfaces under very severe operating conditions, and simulating the entire transition from the fill film EHD, mixed, down to boundary lubrication. In the present study a set of sample cases in a circular contact is analyzed. Three typical machined surfaces are used, representing different types of topography and orientation. The original RMS roughness (before deformation) is adjusted to 8 different levels, from 0.1 μm up to 1.5 μm, in order to cover a practical range for industrial applications. Results show that in the typical mixed EHL the maximum pressure, contact load ratio, friction, flash temperature as well as maximum subsurface shear stress, are all increased significantly as the roughness increases. The effect on the average film thickness (or gap), however, is relatively limited.