A treatise on material characterization in the metal cutting process. Part 2: cutting as the fracture of workpiece material

摘要

Part 1 of this two-part paper presents a novel approach to the characterization of the resistance of workpiece material to cutting. It is shown that the strain at fracture is the most general material behavior characteristic. This second part offers a novel approach towards the meaning of plasticity in metal cutting and its relationship to the strain at fracture. It is shown that the strain-rate sensitivity is one of the plasticity criteria. The influences of defect population in metals and the state of stress in the deformation zone on fracture in metal cutting are considered. It is shown that, by changing the state of stress, the strain at fracture and thus the energy consumption in cutting can be varied over a wide range. This approach appears to be a new ground for choosing cutting tool geometry and cutting regime. The final part of the paper establishes that ductile fracture along the line which separates the layer to be removed from the rest of the workpiece takes place in metal cutting. For the first time, a definition of the metal cutting process is proposed.