Modeling of the Ultra-Precision Machining Process Using New Combined Molecular Dynamics/Monte Carlo (MD/MC) Simulation

Oklahoma State University, Stillwater OK

Investigators

Abstract

This grant provides funding for the development of techniques for the simulation of machining at the atomic level, known as, molecular dynamics (MD) simulation. The following three important areas of simulation that would have a significant impact on our understanding of the cutting process will be considered. They are: (1) simulations of machining at conventional cutting speeds, never before attempted due to long processing times involved with conventional MD simulations, (2) simulations of machining of semiconductor materials, such as silicon, germanium with a diamond tool. Also, included under this category are the simulations of machining of iron with a diamond tool to investigate the chemical nature of wear and simulations of machining of bcc (body centered cubic) and hcp (hexagonal close packed) materials (in addition to fcc (face centered cubic) metals currently being modeled), using the Modified Embedded Atom Method (MEAM), and (3) use of parallel processing in a distributed computing environment (or Beowulf cluster) to significantly reduce the computational time per run so that large size work pieces (up to 1 million atoms) or lower cutting speeds can be considered. The hybrid Molecular Dynamics/Monte Carlo (MD/MC) approach enables addressing of the machining problem at conventional cutting speeds. In MC simulations, time (or the cutting velocity) is not an explicit variable as one is concerned with a series of equilibrium states. However, it is involved indirectly through the temperature in the cutting process. If one knows the temperature distribution at conventional cutting speeds a priori, then this information can be used as an input to the MC moves. The work proposed under this grant will enable determination of mechanical properties of semiconductor materials at nanoscale for application to microelectromechanical systems (MEMS), and for ultraprecision machining of a wide range of materials (both metals and semiconductor materials). It may be noted that experimental techniques require very expensive high precision, high rigidity machine tools in a temperature controlled environment and costly single crystal diamond tools. The simulations can provide adequate information such that only a few tests to verify the MD simulation results are necessary. The new hybrid MD/MC approach also enables use of larger size workpieces (up to a million atoms) and cutting speeds close to conventional.