Analytical modeling of residual stress formation in workpiece material due to cutting

• The authors in this paper observe that stress of a point in workpiece during cutting is time dependent, and then propose that initial condition must be determined in relaxation procedure in order to calculate residual stress.
• Furthermore, the authors propose a criterion to determine the initial condition based on calibration of surface residual stress. It shows that the computed residual stress in different depth below workpiece machined surface based on the criterion is consistent with experimental results.
• The computed results of the proposed model show that the residual stress component in cutting speed direction is higher than that of in axial direction, which is consistent with the general conclusion of the existing literatures on experimental or numerical study of residual stress in cutting. Then the authors provided an explanation of the relationship of residual stress components based on the analysis of cutting stress using the proposed model.

Residual stress on surface layer of workpiece has significant effects on service life of parts, including fatigue strength and corrosion resistance. Metal cutting process is widely used on manufacturing parts, which will cause severe mechanical and thermal stress on the material and then result in the formation of residual stress on workpiece surface layer. A thorough analysis of residual stress formation due to cutting is essential to create parts with desired residual stress distribution. After analyzing stress field in workpiece based on previous work, the authors in this paper observe that stress of a point during cutting is time dependent, and then proposed that initial condition is mandatory in order to determine initial stress state in stress relaxation procedure. Then the authors propose a criterion to determine initial condition based on the calibration of surface residual stress. Using this criterion and calibration method, the residual stress in different depth of machined surface can be compute using the proposed analytical residual stress model, and the computed results are consistent with experiment results. Moreover, the computed results show that the residual stress component in cutting speed direction is higher than that in axial direction, which is consistent with the general conclusion in the existing literatures. The proposed concept of initial condition and its calibration method in stress relaxation promote the understanding of physical mechanism of residual stress formation in cutting, and can be extended to the situations where the evolution of flow stress in workpiece during cutting is similar with that of in orthogonal cutting.