A treatise on material characterization in the metal cutting process. Part2: cutting as the fracture of workpiece material

Part 1 of this two-part paper presents a novel approach to the characteriza tion of the resistance of workpiece material to cutting. It is shown that t he 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 sho wn 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 de formation zone on fracture in metal cutting are considered. It is shown tha t, by changing the state of stress, the strain at fracture and thus the ene rgy consumption in cutting can be varied over a wide rang. This approach ap pears to be a new ground for choosing cuffing tool geometry and cutting reg ime. The final part of the paper establishes that ductile fracture along th e line which separates the layer to be removed from the rest of the workpie ce takes place in metal cutting. For the first time, a definition of the me tal cutting process is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.