Molecular dynamics nano-scratching of aluminium: a novel quantitative energy-based analysis method

Atomistic models for friction suffer from the severe length- and time-scale restrictions of molecular dynamics. Even when they yield good qualitative results, it is difficult to draw meaningful quantitative conclusions from them. In this paper, a novel approach to quantify the scratching work and the energy associated with the creation of plastic zones is presented. The approach is combined with a statistical criterion to determine the significance of simulation box size and sliding rate effects on the friction coefficient. These two methods are applied to a large parametric molecular dynamics study of single-crystal single-asperity aluminium nano-scratch with varying simulation sizes, indentation depths and scratching speeds in order to analyse these size and rate effects. The results show that the simulation size effects are a considerable obstacle to understanding the atomistic origins of friction - using present-day computing hardware - as they have a strong influence on the core mechanisms of sliding friction. A motivation for the development of a new 3D multi-scale method for a hybrid nano- and micro-scale description of plasticity is formulated. (C) 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of Dr. Oana Cazacu.