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

这项拨款为原子水平的机械加工模拟技术的发展提供资金，称为分子动力学（MD）模拟。将考虑以下三个重要的模拟领域，它们将对我们对切削过程的理解产生重大影响。它们是：(1)在传统切削速度下的加工模拟，由于传统MD模拟涉及的加工时间长，以前从未尝试过；(2)用金刚石工具加工半导体材料（如硅、锗）的模拟。此外，在这一类别下还包括用金刚石工具加工铁的模拟，以研究磨损的化学性质，并模拟加工bcc（体心立方）和hcp（六边形紧密堆积）材料（除了fcc（面心立方）金属目前正在建模），使用改进的嵌入原子方法（MEAM）。(3)在分布式计算环境（或Beowulf集群）中使用并行处理，以显着减少每次运行的计算时间，从而可以考虑大尺寸工件（多达100万个原子）或更低的切割速度。混合分子动力学/蒙特卡罗（MD/MC）方法可以解决传统切削速度下的加工问题。在MC模拟中，时间（或切削速度）不是一个显式变量，因为它与一系列平衡状态有关。然而，它是通过切削过程中的温度间接参与的。如果先验地知道传统切割速度下的温度分布，那么该信息可以用作MC移动的输入。在这项资助下提出的工作将能够确定纳米级半导体材料的机械性能，用于微机电系统（MEMS），以及各种材料（金属和半导体材料）的超精密加工。值得注意的是，实验技术需要非常昂贵的高精度、高刚性机床和昂贵的单晶金刚石工具。模拟可以提供足够的信息，因此只需要进行少量试验来验证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（高达一百万个原子）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.