Research On Modeling Optimization And Thermoplastic Instability For High Speed Milling Of 3Cr2W8V Die Steel

High speed machining has become one of the most effective methods to solve the problem of difficult to machine materials,it is also need to optimize the cutting parameters for the best state process system,and to obtain high machining accuracy and production efficiency.The thesis mainly focus on typical and widely used 3Cr2W8V die steel,through the analysis of the development and current situation of high speed cutting technology,the modeling and experimental research of cutting deformation and cutting force,to systematicly optimize one kind of die steel of the processing.The main contents and results are as follows:First of all,based on the theory of high speed cutting,the experimental scheme of measuring milling force is designed based on the orthogonal test method,the influence of milling parameters on the milling force in the process of high speed milling 3Cr2W8V die steel is studied.It is found that with the increase of milling speed and rake angle,the milling force decreases;additionally,with the increase of axial cutting quantity,the milling force decreases first and then increases.And,by range analysis,the influence of axial cutting parameters on milling force is highly significant,while the influence of milling speed and radial cutting parameters on milling force is relatively small.Therefore,the milling characteristics of 3Cr2W8V die steel can be effectively improved by using smaller axial cutting amount and feed per tooth,larger milling speed and radial cutting amount.Secondly,the multiple linear regression analysis method is employed to synthesize the orthogonal test data into the milling force prediction model.The regression equation and coefficient of the milling force prediction model are tested by variance analysis.The results show that the regression equation of the established milling force prediction model is highly significant.Among the four regression coefficients,the influence of axial cutting amount on milling force F_x,F_y and F_z is significant,followed by feed amount and milling speed,and the influence of radial cutting amount is the least.Finally,based on the theory of thermoplastic instability,the finite element model is established by Johnson-Cook Viscoplastic Constitutive Equation(JCVCE),and the forming process of continuous and serrated chips in high-speed dry cutting is simulated by using the nonlinear finite element.The effects of different cutting parameters on cutting force,cutting temperature and chip shape are studied,respectively,the results show that the increased cutting speed and axial cutting amount,the temperature of the chip surface increases,will cause obvious the saw tooth,which will weaken along with the increase of the rake angle,and the temperature of the chip surface decreases.In addition,the increase of the axial cutting amount will lead to the increase of the cutting force;the increase of the cutting speed will lead to the decrease of the cutting force;the increase of the tool rake angle will also lead to the decrease of the cutting force.It is found that there is a non-linear relationship between cutting speed and cutting temperature through theoretical calculation,and with the increase of cutting speed and axial cutting amount,the cutting temperature first increases sharply and then tends to increase slowly.