Molecular dynamics simulations of machining, materials testing, and tribology at the atomic scale.

摘要

Scope and method of study. The scale of materials processing in ultraprecision machining (UPM) and micro-electro-mechanical-systems (MEMS) is in the range of a few atomic layers. Consequently, understanding the material behavior under various loading conditions at the atomic regime based on experimentation alone is extremely difficult, time consuming, expensive, and also limited by technological constraints. An alternate approach is to analyze the process by Molecular Dynamics (MD) simulation technique, which is the subject of this investigation. It is shown in this study that MD simulation technique is an extremely powerful and valuable tool in addressing a range of machining, materials testing, and tribological problems.; Findings and conclusions. The results presented in this study are in agreement with the experimental and the simulation findings and at the same time provide solutions to many questions left unanswered based on experimental evidence alone. For example, the simulations on the effect of crystal orientation and cutting direction provided plausible explanations for the high and low shear angles reported by researchers in microcutting of single crystal materials. MD simulations of nanometric cutting and nanoindentation of silicon provided evidence for a plausible transformation of silicon from the α- to β-phase associated with a volume change. The study on the nature of atomic scale friction showed that whenever material removal is involved even at extremely fine scratch depths, the magnitude of friction coefficients can be high, dependent on the rake angle presented by the tool, and independent of the normal force. The material properties measured based on uniaxial tension and nanoindentation experiments are in agreement with the values reported in the literature based on experimentation and theoretical calculations. These results suggest that MD simulation is a versatile and inexpensive tool that can be used with reasonable success to simulate a variety of problems at the atomic scale.