Asperity contact analysis: coupling effects of normal interference and nanoscale offset by molecular dynamics simulations

Abstract

This work investigates the offset contact behaviors of nanosized asperity with spherical and non-spherical shapes, aiming to provide a more realistic analysis of asperity contact for rough surfaces. Molecular dynamics models of nanosized asperity are established, using diamond and copper as exemplary materials. Differences between offset and non-offset contacts, as well as spherical and non-spherical asperities are compared through atomic variations including displacement, shear strain and structure. Coupling effects of normal interference and nanoscale offset on asperity contact behaviors are further analyzed. Comparisons between the established models and the microscopic asperity models in contact force-interference dependence are conducted for verification. Results indicate that atoms in central contact region move vertically with smaller shear strains, while those in peripheral region primarily move diagonally outward with larger shear strains due to directional atomic slip motion. Furthermore, the spherical asperity shows higher atomic deformation and contact force compared to the non-spherical asperity for identical interference and offset conditions. Additionally, the shear resistance of single-crystal copper with {100} crystal orientation can be enhanced along the [1 1 0] and [1 − 1 0] directions.