Contact area and static friction of rough surfaces with high plasticity index

A model for the contact area and static friction of nominally flat rough surfaces and rough spherical surfaces is presented. The model extends previously published models, which are limited to plasticity index values below 8, to higher plasticity index values by accounting for fully plastically deformed asperities based on finite element results by Jackson and Green [2005,"A Finite Element Study of Elasto-Plastic Hemispherical Contact Against a Rigid Flat," Trans. ASME, J. Tribol., 127, pp. 343-354]. The present model also corrects some deficiencies of the earlier models at very small plasticity index values below 0.5.