Numerical Analysis Of Metal Cutting Process

Manufacturing is one of the most important ways in the industrial world because of its practical value in aerospace, automobile as well as machine producing, and at present metal cutting is the crucial way of manufacturing the industrial products. Metal machining is also a very complicated process considering its thermal-force coupling effect, including strain hardening effect, strain rate strengthing effect and thermal softening effect, which is related to a comprehensive application of the different subjects such as machining theory, thermodynamics and tribology and so on. As the development of computer science and the improvement of the theory of finite element method(FEM), the means to study the cutting process is more and more diverse, including analytical modeling, experimentation and numerical simulation.Firstly, this part gives an overall picture of studies about the simulation of cutting process in the domestic academic fields and abroad. Then the theory of cutting process is introduced briefly, including the geometry model, friction model, and the generation and transfer of heat during the process. Finite element method and the basic procedures of application of FEM are discussed, the critical problems in building FE model are clarified, including the material model, friction model, the principle of chip separation and heat transfer model. These two parts are the important fundamentations to start the later scientific analysis in the next chapters.Secondly, this work focuses on the effects of cutting edge geometries on cutting process, such as the distributions of stress, strian and temperature in orthogonal cutting of AISI 1045 material using FEM simulation with sharp, chamfered, double chamfered and blunt tools. The cutting process is simulated with Arbitrary Lagrangian-Eulerian(ALE) approach in the commercial Software ABAQUS/Explicit with the very classical Johnson-Cook material constitutive model adopted. The simulation results suggest that the tool edge geometry influences the shape of “dead metal zone”(DMZ) considerably, while having little influence on the chip formation. An analysis of thermo-mechanical coupling was also conducted, and the results show that the stress distribution is affected by the temperature distribution and cutting speed because of the thermal softening effect and the strain rate hardening effect. A common analytical model is introduced to predict the residual stress, and equivalent Mises residual stresses are all calculated with four different tools to suggest that the tool edge geometry has a significant effect on the residual stress. Meanwhile, mechanism of the DMZ formation, the effects of tool edge geometry and cutting speed on the DMZ during chip formation in orthogonal cutting of AISI 1045 material using FEM were investigated. The simulations are validated by the experimental findings and analytical data of cutting and thrust forces. Simulation results show that the cutting speed has some effects on the formation of the dead metal zone, while tool edge geometry has large influences on the formation of DMZ because of the missing region created by different edges. The machining forces both in the cutting and thrust directions increases as the size of the DMZ increases and decreases as the cutting speed increases due to the decrease of the DMZ. The DMZ is more responsible for the increase of thrust force than cutting force. Chip type are determined by the combined effects of workpiece material properties, cutting speed, uncut chip thickness, feed rate and tool geometry during machining.Last but not least, serrated chip, one of the most important chip types, was investigated in hard cutting from low to high speed. In this chapter, a new analytical model has been proposed to better understand the formation of serrated chip as well as new material hardening model, and the simulations have been acquired using ABAQUS/Explicit in machining AISI 1045 during different speeds(from 60 to 6000 m/min). It has been shown that stress is influenced simultaneously by the strain rate hardening and temperature softening. Also, it can be found that the hardening ratio increases when the cutting speed rises. The results of the simulations and experiments correlated well. The cutting force and thrust force both decrease as the cutting speed increases, and the difference between them will shrink when the machining speed reaches a high level. The formation of single serration is also investigated, and the numble of serration correspond to the fluctuate of force and enegy curves.