A Static Friction Model for Elastic-plastic Contacting Surfaces Using Statistically Homogenized Technique

An improved static friction model is developed for elastic-plastic contacting surfaces. Two random variables of asperity height and curvature for Gaussian isotropic contacting surfaces are assumed to govern asperities distribution and they satisfy a joint probability distribution function. Based on the contact parametric representation of the KE model proposed by Kogut and Etsion, the expected macroscopic values of normal stress and shear stress are obtained by using statistically homogenized technique. Then the effect of roughness, the energy of adhesion and material properties on static friction coefficients are studied and the results show similar trend with literatures. A comparison of the present model with the SV friction model proposed by Sista and Vemaganti shows that the adhesion force has a more significant effect for smoother surface and SV model is more suitable for heavily loaded contacts. The static friction coefficient is related to the ratio of hardness to elastic modulus H/E. At the same roughness and normal load, lower H/E leads to lower critical interference omega(c), higher plasticity index psi, and smaller static friction coefficient.