Molecular dynamics simulation on microcutting process of monocrystalline silicon

摘要

To understand the mechanisms of material removal at extremely small depth of cut and brittle-ductile transition in material removal process, molecular dynamics (MD) computer simulations of microcutting of defect-free monocrystalline silicon are carried out. MD simulations show that chip removal under nanometric undeformed chip thickness takes place in ductile mode as a result of “viscous flow” of amorphous region following the phase tramsformation from crystalline to amorphous by plowing of cutting edge. The work surface shows amorphous structure with large tensile residual stress. The simulation also suggests that the critical depth of cut can be governed by tensile stress level intermittently generated as a result of the interference between the stresses generated by static cutting force and dynamic elastic wave emitted when the crystalline structure is crushed in front of cutting edge. Therefore, in case of cutting under large undeformed chip thickness, brittle mode material removal and/or sub-surface damage may take place even on a defect-free brittle material.