| Abstract: | A slip-line field model for orthogonal cutting with chip breaker and flank wear has been developed. For a worn tool, this slip-line field includes a primary deformation zone with finite thickness; two secondary shear zones, one along the rake face and the other along the flank face; a predeformation zone; a curled chip; and a flank force system. It is shown that the cutting geometry is completely determined by specifying the rake angle, tool-chip interface friction and the chip breaker constraint. The chip radius of curvature, chip thickness, and the stresses and velocities within the plastic region are readily computed. Grid deformation patterns, calculated with the velocity field determined, demonstrate that the predicted effects of changes in frictional conditions at the tool-chip interface and of the rake angle on chip formation are in accord with experimental observations. The calculated normal stress distribution at the tool-chip interface is in general agreement with previously reported experimental measurements. The model proposed predicts a linear relationship between flank wear and cutting force components. The results also show that non-zero strains occur at and below the machined surface when machining with a worn tool. Severity and depth of deformation below the machined surface increases with increasing flank wear. Forces acting on the chip breaker surface are found to be small and suggest that chip control for automated machining may be feasible with other means. |
