Collaborative Research: Accelerated Large-Scale Simulation Study of Atomic-Scale Wear Using Hyper-Quasicontinum

This collaborative award supports research on the mechanics of wear mechanisms occurring at the atomic scale. A novel predictive computational approach, the hyper-quasicontinuum (hyper-qc) method, will be employed and advanced. This approach will enable the computational simulation of friction and wear at realistic sliding speeds with atomic resolution of critical events and spatial domains. The simulation results are expected to lead to new insights into the fundamentals of atomic-scale wear. Such knowledge is a prerequisite for predicting wear at macroscopic length scales. Hence the outcomes will provide valuable insight into the improved engineering of structures and materials with the aim of wear reduction. Wear of conventional mechanical parts has been conservatively estimated to cause a loss equivalent to approximately 1.5 percent of an industrialized nation's Gross Domestic Product. For the United States, this corresponds to about 250 billion dollars in 2013. The problems arising from wear are even more critical in the newly emerging field of nanotechnology. Wear significantly hampers the adoption of systems with moving parts. Thus, the outcomes would enable further advances in nanotechnology. All computer codes established as an outcome of this project will be made freely available to the research community via dedicated web portals (qcmethod.org and openkim.org). The collaborative project will provide training for graduate students. An outreach program for science and engineering education will be organized with local high schools in Cincinnati whose student populations are predominantly from underrepresented groups.

The ultimate aim of this project is to develop a novel predictive model for nano-scale wear, which can be used to reduce wear at macroscopic length scales. The research approach is based on the use of the hyper-qc method. To enable the analysis of wear, methodological innovations to advance the hyper-qc method are necessary. These advances would enable the method to deal with multiple time-scales. A novel approach for coupling of atomistic and continuum regions accounting for heat transfer will also be established. The hyper-qc method will make it possible to consider key experiments on atomic-scale wear. Simulating will capture all relevant features of wear experiments with an atomic force microscope apparatus. Thereby, atomic resolution is retained in the contact region and sliding speeds comparable to actual experiments are considered. Wear simulations will consider various engineering materials of technological interest including silicon, silicon-oxides, and diamond-like carbons. From the hyper-qc simulations it will be possible to identify the atomic-scale mechanisms responsible for wear at the nano-scale and to study their dependence on important experimental conditions such as sliding velocity and temperature. Conflicts between simulation results and experimental data and observations will be used to improve existing models for nano-scale wear.