Towards a deeper understanding of wear and friction on the atomic scale—a molecular dynamics analysis

This study aims to gain an in-depth understanding of the mechanisms of wear and friction on the atomic scale through the investigation of a typical diamond-copper sliding system with the aid of molecular dynamics analysis. The study revealed that there generally exist four distinct regimes of deformation, i.e. the no-wear regime, adhering regime, ploughing regime and cutting regime. The transition between these regimes is governed by key sliding parameters such as indentation depth, sliding speed and surface lubrication conditions. The no-wear regime exists for a wide range of indentation depths and thus a no-wear design of practical sliding systems is possible even under chemically clean conditions. In the cutting regime, the frictional behaviour of the system follows a proportional law. In all the other regimes, however, the variation of the frictional force is complex and cannot be described by a simple formula. The study also pointed out that on the atomic scale the slip lines generated by dislocation motion are very different from those predicted by the slip-line theory of plasticity. A new theory needs to be developed to bridge the gap between atomic and micro analyses.