Interfacial effects on the dynamic stresses in high speed cutting of heterogeneous materials

The microstructure of materials has an important effect on the chip formation and fracture process during metal cutting. Its heterogeneity makes the dynamic mechanical response of materials complicated, which would become more notable with the increase of cutting speed. In this paper, a spring-network discrete element model was established to characterize the heterogeneous material for cutting simulation. The dynamic stress propagation was investigated during the cutting tool impacting on the workpiece at high speeds. Voronoi tessellation method was utilized to create polycrystalline structures in the model and the stress distribution was discussed. Compared with the results by the homogeneous model, the distribution of dynamic stress in polycrystalline model is obviously discontinuous. Furthermore, the normal stress and shear stress propagates in the workpiece as longitudinal and transverse stress waves, which are reflected and transmitted at interfaces. The fluctuation of stress triaxiality is more obvious and changes significantly with the increase of cutting speed, which provides an idea for explaining the fracture mode transition of material in high speed cutting process.