Molecular simulation of tip wear in a single asperity sliding contact

Molecular dynamics simulations were carried out to investigate the wear formation of a truncated-cone-shaped tip sliding against a rigid flat substrate. Under a constant normal load, the worn volume of the tip increases sub-linearly with the sliding distance, which holds true for three distinct debris definitions (geometry-based, material-transfer-based and displacement-based). Under a constant normal stress, the tip height reduces linearly with the sliding distance, which can be conveniently used to calculate the wear rate. It was found that the tip height loss per sliding distance (ΔH/ΔL) is a function of the normal stress and the tapering angle of the tip, but independent of the sliding speed and the contact area. Above a critical stress, ΔH/ΔL increases linearly with the stress while the debris is generated from plastic flow. ΔH/ΔL is almost zero below the critical stress while the debris is generated from atom-by-atom attrition. Our results show that Archardʹs linear wear law is not applicable to single-asperity tip wear in the plastic wear regime. Finally, a new wear rate formula is given for tip wear as a function of the load, the contact area and the tapering angle of the tip.