Plastic strain analysis of the surface damage in metal cutting.

摘要

The machining process introduces a substantial amount of plastic deformation into the surface and subsurface of the workpiece and affects the surface integrity. An analytical model was developed through plastic strain analysis to estimate the depth of plastic deformation and the surface shear strain using readily measurable machining parameters and true stress-strain characteristics of the workpiece material.; Experimental validation was carried out with a quick-stop device, workpieces with cemented grids attached, and true stress-strain curve data was carried out on 6061-T6 aluminum alloy and 1020 carbon steel to verify the analytical models developed. A statistical analysis was used to examine the effect of experimental variables on the depth of plastic strain and the surface shear strain.; The depth of cut, rake angle and cutting speed influenced the depth of plastic deformation and the surface plastic flow, but their effect on the surface shear strain was inconclusive. Both the depth of plastic deformation and the surface plastic flow decreased with an increase in rake angle and cutting speed, and with a decrease in depth of cut. Variations in the depth of plastic deformation, the surface plastic strain and the surface plastic flow with experimental variables were explained in terms of the associated variables in the analytical model. Validation of the analytical model showed the average difference between the measured and computed depth of plastic deformation was 13.7% for 1020 carbon steel and 39.1% for 6061-T6 aluminum alloy (due to deviation from plane strain conditions), whereas the average difference in the surface shear strain was 15.3% for 6061-T6 aluminum alloy and 14.7% for 1020 carbon steel.