Effect of tool geometry in nanometric cutting: a molecular dynamics simulation approach

摘要

To investigate the effect of tool geometry in nanometric cutting, molecular dynamics (MD)simulations of nanometric cutting were carried out with tools of different edge radii relative to depthof cut. Simulation studies were carried out by varying the tool edge radius, r (3.62 21.72 nm) anddepths of cut, d (0.362-2.172 nm) by maintaining the d/r ratio constant (0.1, 0.2, and 0.3). Variationsof the cutting and thrust forces, the force ratio, the specific energy, and the sub-surface deformationwith the tool geometry and depths of cut were investigated and found to have a significant influenceon them. The results were also found to be in reasonably good agreement with the experimental andsimulation results reported in the literature. Unlike in conventional cutting where the depth of cut issignificant compared to the edge radius (or, the edge radius is negligible), in nanometric cutting this isgenerally not the case due to small depths of cut and minimum possible edge radius that can beproduced on a single crystal diamond tool by the best manufacturing practice (20-70 nm). It alsoappears that the high negative rake angle and/or large edge radius (relative to the depth of cut) of thetool used in practice for finishing of advanced materials such as silicon wafers in nanometric cuttingprovides a high hydrostatic pressure underneath the tool required for the formation of a small plasticdeformation zone immediately beneath the tool instead of initiating brittle fracture. A material removalmechanism was proposed that would cover the range from conventional machining to grinding, toultraprecision machining, and finally to the indentation-sliding as a cognate transition for materialremoval operation. Indentation-sliding model appears to be more appropriate when consideringmachining brittle materials with tools of large edge radius relative to the depth of cut or large negativerake tools. Similarly, for grinding of ductile materials, the appropriate model would be using eithertools of large edge radii relative to the depth of cut or large negative rake tools.