Invited Paper TR+NS-ThM1
Temporal and Spatial Multiscale Simulations of Low-Velocity Frictional Sliding

Thursday, November 13, 2014, 8:00 am, Room 303

As the size of mechanical systems of technological interest such as micro electro-mechanical systems (MEMS) decreases, the need to develop experimental and theoretical tools to investigate micro/nanometer scale phenomena has been growing rapidly. Since its invention in 1986, the Atomic Force Microscope (AFM) has been a primary tool to study the atomic-scale friction and wear and atomistic simulation methods such as molecular dynamics (MD) have also been widely used because these simulations can provide direct access to atomic-scale mechanisms which cannot be observed experimentally. However, there is a great disparity in length and time scales between the simulated systems and the real experimental systems. One of the significant artifacts of these scale differences is that systems are loaded at by several orders of magnitudes larger rates in simulations than in experiments, which may completely distort the underlying mechanisms. Recently, a novel multiscale method, called hyper-QC, which can span both length and time scales simultaneously has been developed. Hyper-QC combines quasicontinuum (QC), a spatial multiscale method, and hyperdynamics, an accelerated MD scheme, in a single platform. In this talk, the hyper-QC simulation results of AFM experiments will be presented. Hyper-QC enables the reduction in the sliding rate by two or three orders of magnitudes from that of the conventional MD scheme as well as the reduced effective number of atoms that is achieved through the QC coarse-graining.