The Behavior of Surface Roughness in EHL Contacts Under Small Slide to Roll Ratios

The amplitude attenuation theory represents a possible way how to predict the tribological performance of a surface having general roughness. There are applications of this theory for pure rolling and rolling–sliding conditions having different governing parameters. Obviously, pure rolling case is much simpler and it was already experimentally verified. Conversely, rolling–sliding conditions represent much complex case and its solution is still under development. Nevertheless, a lot of machine components operate under the conditions where only small slide to roll ratios are present. This study was carried out to find the reasonable validity of the pure rolling model for the applications where small amount of sliding is present. The behavior of roughness was observed under conditions of small sliding speed using optical tribometer for film thickness mapping. The results were analyzed and compared with the predictions according the amplitude attenuation theory for both pure rolling and rolling–sliding cases. The influence of slide to roll ratio on roughness profile shape was studied and differences to the pure rolling profile were evaluated. It was concluded that the pure rolling model can be applied with reasonable precision within the range of slide to roll ratios from −0.15 to 0.1. The correlation coefficients are better than 0.85, the RMS value changes are less than 3 %, and bearing area curves are almost unaffected.