VISCOPLASTIC ANALYSIS OF METAL-CUTTING BY FINITE-ELEMENT METHOD

Determination of the primary shear deformation zone (PSDZ) to evaluate tool-chip interface temperature and forces during metal cutting proce sses is important. Evaluation of the PSDZ can be performed either expe rimentally or analytically. Experimental methods are cumbersome and ti me-consuming. Hence, an analytical method is proposed. Metal undergoes a large plastic deformation during cutting and behaves like an incomp ressible, non-Newtonian fluid. The material behaviour, therefore, is m odelled by a viscoplastic constitutive equation. Temperature effects a re included by evaluating the material properties at a typical average temperature usually encountered in the cutting zone. Only orthogonal steady state machining is considered so that the problem of metal flow in the cutting zone can be modelled as a two-dimensional, steady stat e problem. The finite element method (FEM) is used to convert the cont inuity and momentum equations to a set of non-linear algebraic equatio ns that are solved by the frontal method. The results obtained for the average shear strain rate, shear flow stress and mean width of the PS DZ compare favourably well with the experimental results. The PSDZ is found to depend basically on feed rate and cutting speed for a given w orkpiece material, which is consistent with the experimental observati ons of others. It is concluded that a 3% cut-off for the maximum strai n invariant can be used to determine the mean width of the PSDZ.