Modeling of ductile cutting of tungsten carbide

A theoretical and experimental study on ductile cutting of tungsten carbide by using CBN tools is presented. In this study, the ductile chip formation process in cutting of tungsten carbide is modeled based on analysis on the cutting forces, cutting process geometry, and fracture mechanics. The cutting forces are modeled as functions of the tool geometry, workpiece material properties, and friction between the tool and chip. The cutting geometry is modeled using an equivalent tool rake angle and an equivalent shear angle. The transition of brittle chip formation to ductile chip formation in the cutting process is modeled based on the fracture toughness and the workpiece material properties. Experiments are conducted to verify the model for the critical undeformed chip thickness, which show a substantial agreement between predicted and experimental results. It is also shown by SEM observations of the machined surface of tungsten carbide workpiece that crack propagation in tungsten carbide under cutting is the main cause of brittle fracture, and the crack propagation relates directly to the undeformed chip thickness.