Contact area on rough surface of nonlinear isotropic brittle materials

An asperity profile function has been proposed that describes the isotropic rough surface of a material. The function is parameterized with three new roughness parameters that control the root mean square height, the slope and the curvature of the rough surface, respectively. Unlike the roughness parameters used in the well known Greenwood-Williamson model, the three parameters introduced in this paper are independent of each other, which is an advantage as this facilitates the characterization of the isotropic random surface of the material. However, a disadvantage with this parameterization is that the roughness parameters are not linked to a contact area equation any more, like the Hertz equations that express contact with linear materials. Different asperity profiles defined by the new roughness parameters were analyzed by a 2D axial symmetric FE-model. The numerical results suggest a procedure for developing a contact area function that are parameterized with the three new roughness parameters, which is also suitable for nonlinear brittle materials.