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

该补助金为原子级加工模拟技术的开发提供资金，称为分子动力学（MD）模拟。以下三个重要的模拟领域将对我们理解切削过程产生重大影响。它们是：（1）以常规切削速度的加工模拟，由于常规MD模拟涉及的长加工时间，以前从未尝试过，（2）用金刚石工具加工半导体材料（例如硅、锗）的模拟。此外，这一类别下还包括用金刚石工具加工铁以研究磨损的化学性质的模拟和体心立方加工的模拟。（体心立方）和HCP（六方密堆积）材料（除了目前正在建模的fcc（面心立方）金属之外），使用改进的嵌入原子方法（MEAM），以及（3）在分布式计算环境（或Beowulf集群）中使用并行处理，以显著减少每次运行的计算时间，使得可以考虑大尺寸工件（高达1百万个原子）或较低的切割速度。混合分子动力学/蒙特卡罗（MD/MC）的方法，使在传统的切削速度的加工问题的解决。在MC模拟中，时间（或切割速度）不是一个明确的变量，因为它涉及一系列的平衡状态。然而，它是通过切削过程中的温度间接参与的。如果事先知道在常规切割速度下的温度分布，则该信息可以用作MC移动的输入。根据这项赠款提出的工作将能够确定半导体材料在纳米尺度上的机械性能，以应用于微机电系统（MEMS），并用于各种材料（金属和半导体材料）的超精密加工。可以注意到，实验技术需要在温度受控环境中的非常昂贵的高精度、高刚度的机床和昂贵的单晶金刚石工具。模拟可以提供足够的信息，使得仅需要几个测试来验证MD模拟结果。新的混合MD/MC方法还可以使用更大尺寸的工件（高达100万个原子）和接近传统的切割速度。

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.