Effects of rough surface topography and orientation on the characteristics of EHD and mixed lubrication in both circular and elliptical contacts

Effects of rough surface topography and orientation on the characteristics of EHD and mixed lubrication are investigated in this paper by using a numerical approach recently developed by the present authors. This approach is capable of handling measured engineering surfaces under very severe operating conditions, and simulating the entire transition fi om the full film EHD continuously down to boundary lubrication. In the present study, three typical machined surfaces are employed for cases in circular contacts: a shared surface with nearly isotropic topography, a transversely ground surface and a longitudinal ground surface. For elliptical contacts (ellipticity 4.0), 3-0 sinusoidal wavy surfaces with different wavelengths in x- and y-directions are used. More than 80 cases have been analyzed, covering a very wide range of operating conditions, including full film EHD, mixed and boundary lubrication. The results indicate that at low lambda ratios, the average film thickness in rough surface contacts is often slightly greater than that in smooth surface contacts. Generally speaking, the surface topography and orientation may have quite noticeable effects on the asperity contact area and load sharing, but only a limited (in many cases insignificant) influence on the average film thickness (or gap) in both the circular and elliptical contacts.