Sensitivity of Shear Process in Metal Cutting to the Development of Residual Stress

Machining processes are widely used for producing a component by material removal. Material is removed in the form of chips through the action of the wedge-shaped cutting tool. As the tool proceeds, the material is first elastically deformed, and then plastically deformed. The mechanism of plastic deformation in metal is dislocation movement Typical machining processes include turning, milling, drilling, shaping and grinding. It is known that the chip formation process in metal cutting is quite unique in many ways [1]. First, the process is a localized, asymmetric deformation that takes place at very large strains and exceptionally high strain rates in a small deformation zone. Typical values for strains and strain rates range 2 to 5 and 104 to 109 per second, respectively. Second, it is relatively unconstrained in that the only external constraint is the length of contact between tool and chip on the rake face of the tool. On the rake face there may be seizure as well as sliding friction. Machining introduces a large amount of plastic deformation in the workpiece material and chip. This plastic strain is nonuniform, and therefore residual stresses are induced in the workpiece surface and subsurface throughout, and slight below, the depth of plastic deformation. Thus, residual stresses are often an undesirable but unavoidable by-product of machining