Atomistic simulation of the effect of roughness on nanoscale wear

At the macroscale, it is expected that surface roughness decreases adhesive wear and increases abrasive wear, and both increase with load. Here we evaluate whether these trends are also applicable to nanoscale contacts. Molecular dynamics simulation is used to model dry sliding of Si atomic force microscope tips with varying roughness on a Cu substrate at a range of normal loads. Surface wear is quantified as the number of substrate atoms displaced during steady-state sliding and characterized as a function of tip roughness and load. The interaction energy between the tip and substrate and a geometric roughness factor are used to investigate the contributions of adhesive and abrasive wear. By predicting how roughness affects nanoscale wear, and isolating the adhesive and abrasive wear modes, it is possible to describe the relationship between roughness, load and wear and, further, to determine an optimum tip roughness that will minimize wear at a given load. (C) 2015 Elsevier B.V. All rights reserved.