Possible mechanism of brittle-ductile transition in material removal in micromachining of brittle materials

To understand the mechanisms of material removal at extremely small depth of cut and the transition in material removal from brittle to ductile in machining of defect-free brittle material, computer simulations of micromachining of monocrystalline Si are carried out based on molecular dynamics (MD). MD simulations suggest that the critical depth of cut can be governed by the amount of energy of elastic waves generated in cutting zone as the results of release of potential energy stored in workpiece by the plowing of cutting edge. Therefore, in case of large scale cutting, brittle mode material removal may take place even on a defect-free brittle material. The surface layer on worksurface shows amorphous structure. As the larger tensile residual strain remains on the worksurface. sub-surface damage may be induced when machined under large uncut chip thickness.