Molecular scale analysis of dry sliding copper asperities

Abstract

A fundamental characterization of friction requires an accurate understanding of how the surfaces in contact interact at the nano or atomic scales. In this work, molecular dynamics simulations are used to study friction and deformation in the dry sliding interaction of two hemispherical asperities. The material simulated is copper and the atomic interactions are defined by the embedded atom method potential. The effect of interference, δ, relative sliding velocity, v, asperity size, R, lattice orientation, θ, and temperature control, on the friction characteristics are investigated. Extensive plastic deformation and material transfer between the asperities were observed. The sliding process was dominated by adhesion and resulted in high effective friction coefficient values. The friction force and the effective friction coefficient increased with the interference and asperity size but showed no significant change with an increase in the sliding velocity or with temperature control. The friction characteristics varied strongly with the lattice orientation and an average effective friction coefficient was calculated that compared quantitatively with existing measurements.