Modelingand analysisof thegritlevelinteractionindiamondwire sawing of silicon

This paper analyzes the interaction between dia- mond grits and crystalline silicon (c-Si) in the ductile regime of diamond wire sawing through theoretical calculations and finite element modeling (FEM). Cutting depth per grit is cal- culated based on the sawing parameters and is found to be in the range of 41 to 143 nm for a typical diamond wire sawing operation. These depths are smaller than the critical depth of cut for brittle-to-ductile cutting mode transition in single point diamond turning/scribing of c-Si as well as the value derived from indentation fracture mechanics. The shape of the cutting grit plays an important role in determining the normal force and the critical depth of cut. The cutting force calculated by the FEM is approximately 12 mN for a spherical grit/indenter shape and 30 mN for a faceted pyramidal (Vickers) indenter at a 70-nm scribing depth. It is shown ductile mode cutting per- formance is sensitive to grit shape, and grits with sharp edges can easily lead to brittle fracture. The theoretical cutting depth per grit indicates the likely dominance of ductile mode cutting in diamond wire sawing, albeit, in reality, it is usually a mix- ture of ductile and brittle cutting. This discrepancy is more likely related to the grit size and shape variation in an actual diamond wire as well as to the dynamics of the operation.