Effects of Skewed Surface Textures on Lubricant Film Thickness and Traction

The effects of surface texture skewness (Ssk) on lubricant film thickness and traction were investigated for elastohydrodynamic lubrication (EHL) contacts. This was accomplished by analyzing three-dimensional simulated surface textures with EHL computational modeling and then verifying the results with rotating ball-on-disk traction experiments. EHL modeling was used to identify critical values for surface roughness average (Sa) and skewness (Ssk) corresponding to a stable lubricant film formation. The critical values were then used to specify test specimen textures that were fabricated for traction experiments. The results from EHL modeling and traction experiments suggest that surfaces with individual skewness Ssk values ranging from −0.4 to −2.2 at constant roughness Sa do not yield significant differences in lubricant film thickness or measured traction. Surfaces with extreme negative skewness Ssk values (approximately −4.7 or lower) may yield significant differences in contact pressure and lubricant film thickness.