Understanding the Mechanisms of Metallic Friction from Atomistic Simulations

Co-authors: Shengfeng Cheng (Virginia Polytechnic Institute and State University), Nicolas Argibay (Sandia)

Tribologists rely on phenomenological models to describe the seemingly disjointed steady-state regimes of metal wear. Pure metals such as gold -- frequently used in electrical contacts -- exhibit high friction and wear. In contrast, nanocrystalline metals often show much lower friction and wear. The engineering community has generally used a phenomenological connection between hardness and friction/wear to explain this macroscale response and guide designs. We present results of recent simulations and experiments that demonstrate a general framework for connecting materials properties (i.e. microstructural evolution) to tribological response. We present evidence that competition between grain refinement (from cold working), grain coarsening (from stress-induced grain growth), and wear (delamination and plowing) can be used to describe transient and steady state tribological behavior of metals, alloys and composites. We explore the seemingly disjointed steady-state friction regimes of metals and alloys, with a goal of elucidating the structure- property relationships, allowing for the engineering of tribological materials and contacts based on the kinetics of grain boundary motion.

Bio:

Michael Chandross received a B.S. in Physics with Electrical Engineering from MIT in 1990, and a Ph.D. in Physics from the University of Arizona in 1996. After postdoctoral positions at SPAWAR Systems Center in San Diego, CA and Sandia National Laboratories in Albuquerque, NM, he joined the staff of Sandia in 2001, where he uses large-scale molecular dynamics simulations to understand the aging and reliability of nanomaterials. He has published more than 50 papers in peer-reviewed journals, is a fellow of the American Physical Society, and serves on the editorial boards of Lubrication Science and Tribology: Materials Surfaces and Interfaces.