Residual stresses after orthogonal machining of AlSl 304: numerical calculation of the thermal component and comparison with experimental results

Residual stresses due to the thermal influence of orthogonal machining have been calculated with a finite element model using stationary workpiece temperatures during cutting calculated with the finite difference method. Calculated results are compared with experimental data obtained with the X-ray diffraction method. In this way, the thermal and mechanical/frictional influences of the machining operation on the workpiece residual stress state can be separated. The influence of cutting speed and cutting depth on machining residual stresses is discussed. It is shown that the thermal as well as the mechanical impact of the orthogonal cutting process causes tensile residual stresses. The mechanical impact of the machining operation causing tensile residual stresses is due to (a) compressive plastic deformation in the surface layer ahead of the advancing tool and (b) greater elastic relaxation upon unloading with respect to the underlying material of a thin, strongly work-hardened surface layer. CHRISTOPH WIESNER, formerly Research Assistant with the Laboratoire de Métallurgie Mécanique, Ecole Polytechnique Fédérale de Lausanne, MX-D Ecublens, 1015 Lausanne, Switzerland.