An improved GW model considering the changing curvature radius of asperities

Abstract

The classical Greenwood and Williamson (GW) model assumes that the asperity is elastic, which does not take into account the changes of curvature radius of the asperity after wearing.On the basis of classical Hertz contact theory and GW model, the shear stiffness formula of the friction surface was derived when the asperity curvature is constant.According to the Mohr-Coulomb criterion, the yield point position of a single asperity under normal pressure and tangential friction force was discussed.And the critical pressure formula for a single asperity was derived, which showed that the pressure corresponds to the radius of curvature of asperity.A model considering the wear of asperities was proposed and the shear stiffness formula of the friction surface considering the changes of the curvature of the asperity was obtained by combining the shear stiffness formula with a constant curvature radius and the critical pressure formula for a single asperity.The calculation results of the model are in a good agreement with the test results.For the specific roughness of rock surface, with the increase of pressure, the rock surface gradually becomes smooth;for different roughness of rock surface, with the increase of roughness, the rock surface is easier to be smoothed.

Keywords

• hertz contact theory
• gw model
• asperity
• shear stiffness
• wear