Research On Analytical Prediction Of Residual Stress In Stainless Steel Machining

Stainless steel is widely used in nuclear industry, chemical industry, medical devicesand food processing industry due to its good corrosion resistance, heat resistance andexcellent mechanical properties. However, stainless steel has the characteristics of highstrain sensitivity, serious work hardening, and low thermal conductivity, which easily leadto thermal deformation and residual stresses in cutting process. Furthermore, thesecharacteristics will affect the performance and service life of workpieces. Therefore,research on the mechanism and prediction model of residual stress in machining difficultto machine materials are of great theoretical significance and practical value.All discussions in this thesis are based on AISI316L austenitic stainless steel. Thethermo-mechanical coupling property in cutting process has been considered in study ofcutting force, cutting temperature and residual stresses, based on which the analyticalmodels for predicting cutting force, cutting temperature and residual stresses areestablished. The prediction model has been verified through the comparison withexperimental results in existing literatures.Cutting force and cutting temperature in stainless steel machining are analyzed. Thecutting force, considering tool edge radius, is calculated based on the unequal divisionshear zone model and Waldorf’s tool force model. The imaginary heat source method isapplied to calculating the temperature distribution during machining process.The mechanism of residual stress in machining is analyzed. An analytical model forpredicting residual stresses due to orthogonal cutting is presented based on the basictheory of metal cutting and thermal-elastic-plastic mechanics. Based on the contactmechanics, isotropic harden model and elastic-plastic loading and unloading theory, theresidual stresses and their distribution in surface and sub-surface of the workpiece due to orthogonal cutting are calculated, with the effect of cutting force and cutting temperatureconsidered. Model predictions are compared with related experimental data; the resultsshow that the model captures the trends of residual stresses produced from orthogonalmachining well. Finally, the effects of cutting speed, feeding rate, rake angle, and tooledge radius on residual stress due to orthogonal cutting are discussed.