Numerical modeling of Ti-6Al-4V alloy orthogonal cutting considering microstructure dependent work hardening and energy density-based failure behaviors

Abstract

Numerical modeling of the cutting process provides an effective method to obtain the micro-scale and instantaneous process information which is difficult to be measured by experiments. A new microstructure (grain size) dependent work hardening plastic (JCM-ms) model was developed to characterize the effect of grain refinement on the cutting process. An energy density-based failure law was applied to control the chip formation and material removal mechanisms ahead of the cutting edge. Orthogonal cutting experiments with different edge radii and uncut chip thickness values for Ti-6Al-4V alloy were carried out to validate the finite element (FE) simulation results. The simulation results were thoroughly validated by the measured principal and thrust forces, segmented chip morphology, and the grain refinement within the machined surface layer. The distribution of grain refinement of the chips and machined surface agreed well with the experimental results. The positions of stagnation points with different edge radii and uncut chip thickness values were measured by the FE simulation results. The variation of surface morphology along the speed direction with larger edge radius is related to the variation of the stagnation points, which will affect the ratio of material being compressed to the machined surface by the tool, during the formation of the adiabatic shear band. The degree of the subsurface shear deformation determines the final distribution of the micro-hardness. Larger shear displacement at the top surface will lead to thicker layer of grain refinement. Residual stresses along the depth from machined surface are mainly related to the displacement normal to the machined surface. The height of the stagnation point is in proportion to the peak compressive stresses induced by the material flow ahead of cutting edge for different conditions. This work provides an effective method to characterize the forces, grain refinement and surface integrity for the orthogonal cutting of Ti-6Al-4V alloy.