The application of roughness model to a soft EHL contact

The study focuses on the development of a numerical model to explore the impact of surface roughness in soft rolling nip contacts, including representation of a real surface. The solution of the governing equations required the application of a multigridding technique to capture the details of the fluid flow within the roughness wavelengths and a minimum number of fluid nodes per wavelength were established. In the case studies, two extreme roughness profiles were considered, longitudinal and circumferential. The longitudinal roughness had a significant impact on nip pressures and pumping capacity, the latter being determined by the minimum film thickness in the nip. The circumferential roughness was found to have a localised effect on film pressure, but only a very small impact on the film thickness profile. The consequent effect on pumping capacity was small.