Research On Cutting Mechanism And Drilling Mechanism Of Deep Hole Based On Energy Field Action

Metal cutting is an important manufacturing technology of mechanical parts.The cutting deformation is accompanied by many macro and micro phenomena such as the work hardening,material failure,microstructure evolution as well as the formation of stress and temperature fields in the cutting deformation zone.These phenomena will affect the cutting force,cutting temperature,the machined surface quality and the mechanism of tool wear and fracture,which is the key to the research of cutting mechanism.However,it is difficult to study the cutting mechanism due to the directionality of stress,the mutual coupling of thermal-mechanical loads and the microstructure evolution involving the dislocation evolution and continuous dynamic recrystallization.Cutting deformation is always accompanied by the energy consumption.The phenomena including the change of material properties,microstructure evolution,and the formation of stress and temperature fields in the deformation zones can be explained by the behavior of energy input,transformation,storage and dissipation.As a scalar,energy has no directivity,which can reduce the difficulty of the study on cutting mechanism.Therefore,in this paper,the energy consumption generated by the microstructure evolution during cutting deformation is modeled and calculated from the micro scale.The models of consumption energy field and stored energy field inside the cutting deformation zone are established,and the cutting mechanism is studied and revealed based on the energy field action.The models of consumed energy,stored energy and dissipated energy considering the high temperature and high strain rate microstructure evolution and work hardening effect during cutting deformation of workpiece material,and the constitutive model based on energy field models and the high temperature and high strain rate microstructure evolution are established.The stored energy-plastic strain curve and stress-strain relationship of deformed materials under different deformation parameters are predicted,and the results show that the flow stress and stored energy both increase with an increase in the strain rate or a decrease in the temperature during deformation.The influence of different deformation conditions on the microstructure parameters is revealed,and the mapping relationship models between the stored energy and the microstructure parameters including the grain size,subgrain size and the number of lattice defects are established.The results show that the grain size is inversely proportional to the stored energy,the subgrain size is inversely proportional to the square root of the stored energy in the form of statistically stored dislocations,and the number of lattice defects is proportional to the stored energy.The consumed energy field model inside the cutting deformation zone is established,and the parameters including shear angle,chip thickness and friction angle at the steady cutting state are determined.The consumed energy field inside the cutting deformation zone,the total energy consumption and the specific cutting energy under different cutting parameters are predicted,and the results show that the increase in cutting speed and feed per tooth can result in the increase in total energy consumption and the decrease in specific cutting energy.The distribution laws of stress field,temperature field and microstructure are revealed based on the consumed energy field inside the cutting deformation zone.The results show that the shear stress distribution inside the cutting deformation zone can be predicted by the consumed energy field and energy balanced relationship.The distribution law of temperature gradient inside the primary shear zone is consistent with that of consumed energy field.The cutting temperature depends on the total energy dissipated per unit time in the primary and secondary deformation zones,and the greater dissipated energy leads to the higher temperature.The stored energy field inside the cutting deformation zone can reflect the distribution law of lattice defect number.The finite element cutting model embedded with the stored energy model is established,and the stored energy field inside the cutting deformation zone is obtained.The results show that the stored energy field presents an obvious gradient distribution in the primary shear zone,the maximum stored energy is located near the main shear plane.The stored energy in the secondary deformation zone is greater than that in the primary shear zone.The relationship models between the stored energy field and these phenomena including the deformation characteristics,subgrain size distribution,stress field,temperature field and work hardening behavior are established.The results show that the deformation distribution characteristics can be well represented by the distribution characteristics of the stored energy gradient inside the cutting deformation zone.The subgrain size and the stress state at any point in the deformation zone can be predicted based on the stored energy field.The heat source region in the cutting deformation zone is consistent with the region with stored energy gradient,and both are located in the primary and secondary deformation zones.The stored energy field near the machined surface can be used to predict the hardening degree of the machined surface and the thickness of the work-hardened layer.The energy field model inside the deformation zone during deep hole drilling considering the particularity of the deep hole drill and the boundary lubrication condition is established,and the consumed energy field and stored energy field inside the drilling deformation zone are predicted.The results show that the total consumed energy and stored energy in the deformation zone corresponding to the external tooth are biggest,followed by the intermediate tooth,and these corresponding to the central tooth are smallest.The cutting power and cutting force can be accurately predicted by integrating the consumed energy field along the radial direction of the drill.According to the distribution law of energy field,the deformation degree of chips generated by each cutter tooth,the stress field and temperature field in the deformation zone,the cutting force as well as the chip breaking conditions are obtained.The results show that the deformation degree of chips generated by the central tooth is largest,followed by the intermediate tooth,and that generated by the external tooth is smallest.The cutting temperature on the external tooth is highest,followed by the intermediate tooth,and that on the central tooth is lowest.The main cutting force and thrust force acting on the central tooth are largest,followed by the external tooth,and the cutting forces acting on the intermediate tooth are smallest.Without considering the tool wear,the chip breaking condition of the central tooth is best,followed by the intermediate tooth and the external tooth.The increase in the feed will significantly improve the chip breaking condition.