The machining allowance and chip thickness can be reduced to less than
approximately 1 μm in ultraprecision manufacturing such as single point diamond
turning (SPDT). Metal surfaces can be finished under precisely controlled machine and
environmental conditions. Accuracies of, respectively, 10 and 1 nm have been attained
in practice and under experimental conditions (aided by advanced control techniques).
Under the highly precise motion of such a machine tool, the primary factor affecting
machining accuracy is the controllability or repeatability of the thickness of cut, that is,
the undeformed chip thickness effectively removed at the cutting edge. Experiments
with a specially prepared fine diamond cutting tool used on such a machine tool have
confirmed that very fine chips, of undeformed thickness as small as 1 nm, can be
removed in the turning of some highly machineable work materials. However, the
accuracy attainable, and mechanisms such as chip formation and surface generation in
microcutting are still not well understood, owing to the limitations in availability of
experimental and measurement techniques, and in analytic methods for studying such
machining conditions. Micro & nanocutting that occurs in a small region which
contains only a few layers of molecules can consequently be atomistic, or discrete in
nature, rather than continuous, as is assumed in conventional continuum mechanics. In
studies of such atomistic processes, which are difficult to investigate experimentally,
computer simulation by molecular techniques is useful. Further advancements in the
machining technology can be aided through a theoretical understanding of micro &
nanomachining. Molecular dynamics (MD) simulation, like other simulation techniques
can play a significant role in addressing a number of machining problems at the atomic
scale. It may be noted that atomic simulations are providing new data and exciting
insights into various phenomenon in micro & nanomanufacturing processes that cannot
be obtained readily by any other theory or experiment. The diversity of these processes
renders difficult of using a generalized theoretical analysis of micro & nanomachining,
however, the methods of molecular dynamics are becoming increasingly attractive for
studies of micromachining, especially as the technology advances toward the shaping of
parts in the nanometric range. The foundations of molecular dynamics that are needed
for theoretical treatments of micromachining therefore form the basis of MNT. Several
such analyzing of micro & nanomachining have been developed. In this chapter, the
principle of molecular dynamics (MD) simulation on micro & nanomachining and the
procedures used to determine the accuracies attainable are described. As noted above,
the case of diamond machining and chemical mechanical polishing are used to illustrate
the technique, although molecular dynamics is now being increasingly used in studies
of many other methods of micro & nanomachining.
Keywords: Molecular dynamics, statistical ensembles, finite differential methods,
interatomic potential functions, geometrical-physical model.
