Modeling energy consumption inside cutting deformation zone to predict the stress distributions, temperature and microstructure by micro irreversible entropic thermodynamics

It is important to analyze the process of chip formation by means of the energy consumption during metal cutting, which is related to the cutting power (or cutting force), the cutting temperature and the machined surface integrity. In this study, the consumed energy field inside the cutting deformation zone is established by considering four micro irreversible processes including the dislocation generation, annihilation, movement, and continuous dynamic recrystallization. A new shear-angle solution is proposed on the basis of the steady conditions of irreversible processes (i.e., the entropy production rate reaches the minimum), whose adequacy is verified by the experimental results of the shear angle and friction coefficient along the tool-chip interface. Based on the predicted consumed energy field inside the cutting deformation zone, the deformation mechanism, microstructure, stress and temperature are predicted and analyzed. The results show that three stages including the loading stage, unloading stage and steady stage are divided during chip formation according to the consumed energy field. The consumed energy and statistically stored dislocation density are both of gradient distribution in the primary shear zone, and continuous dynamic recrystallization is the main mechanism of grain refinement during chip formation, which is dominated in the secondary deformation zone. The stress and temperature inside the cutting deformation zone as well as the hardness of the machined surface are predicted according to the energy balance relationship and consumed energy field, indicating the feasibility of using energy consumption to comprehensively describe the internal changes of workpiece material inside the cutting deformation zone.