Rough contacts between actual engineering surfaces: Part II. Contact mechanics

The models of roughness description by using simple parabolic functions described in Part I are here tested with different contact mechanics models. The approximation with parabolas allows the calculation of each asperity curvature radius, a fundamental quantity for contact mechanics studies. After a review of the main contact mechanics models, some of them has been selected: two different elastic models and two elastic–plastic ones, one with a discontinuity at the boundary between the elastic and the plastic region, and one with an additional elastoplastic transition region. The amplitudes of the contact zone and the load are calculated as a function of the interference of each profile with a rigid smooth flat surface for single parabolic asperities and for whole profiles extracted from five engineering surfaces with different roughness conditions. Big differences in the size of the deformed zone and in the load supported by single parabolas using the different roughness description approaches and contact mechanics models were found. However, these differences are mitigated when the whole profiles are considered. As expected, the elastic models tend to overestimate the load when profiles with a certain degree of plasticity are under investigation. The roughness description approach based on the minimization of the least square error between the measured profile and the parabolic approximation (LMS c1 c2) gives the best simulation of the profile and does not show any drawback from a contact mechanics or numerical point of view. The combination of this approach with the contact mechanics model including the elastoplastic transition developed by Zhao, Maietta and Chang (ZMC) seems to guarantee the best results.