Milling Process Optimization Considering Residual Stress Of Machined Surface

Titanium alloys are widely used in aviation,aerospace,biology,medical and other fields because of their excellent properties.Titanium alloy has complex structure,weak cutting stiffness and high requirements for dimensional accuracy and surface quality,so it is easy to produce nonlinear and strong time-varying problems in the cutting process.In the process of cutting,high cutting temperature and poor thermal conductivity of titanium alloy will seriously affect the surface quality of the workpiece and the life of the tool,and eventually lead to the consistency of the surface quality of titanium alloy workpiece can not be guaranteed.At the same time,the above problems also have a great impact on the distribution of residual stress on the machined surface of titanium alloy,and then affect the deformation,fatigue strength,subsurface damage and stress corrosion of the workpiece,and finally have a great impact on the performance of the titanium alloy workpiece.Based on the above problems,the finite element simulation research on cutting mechanism and cutting process of titanium alloy is carried out.In this thesis,the residual stress distribution on the machined surface of titanium alloy workpiece under thermal mechanical coupling is studied by taking milling processing parameters as the breakthrough point,which provides the basis for the optimization design of cutting parameters,and the design method to meet the requirements of residual stress distribution on the surface of titanium alloy workpiece Process parameters and tool parameters.The main research contents are as follows.Firstly,the spatial edge line mathematical model of the flat-bottomed end mill is established based on the UG environment,and the 3D solid parametric model of the flat-bottomed end mill is obtained based on the method of feature variable setting,which lays the foundation for the finite element numerical simulation study of the residual stress distribution on the machined surface of titanium alloy during milling.Secondly,combined with the key technologies in the finite element cutting simulation process,the finite element simulation software ABAQUS is used to establish the finite element model of residual stress distribution on the machined surface of titanium alloy during the milling process,and the Mises stress cloud diagram of the workpiece and the distribution trend of residual stress layers are obtained through post-processing techniques.Again,a validation milling experiment was conducted on a VDL-1000 E vertical milling machining center,and the residual stress distribution on the machined surface layer during the milling process was measured by X-ray diffractometer,and the simulation results were compared with the experimental results to analyze the causes of errors and to verify that the established3 D milling residual stress layer distribution model of titanium alloy is accurate.Finally,the milling parameters are optimized by genetic algorithm.In this thesis,the distribution of residual stress on machined surface is studied to provide the basis for the optimization design of milling process,and the process parameters and tool parameters are designed to meet the requirements of residual stress distribution on titanium alloy surface.On the basis of improving the surface quality and machining accuracy of the workpiece,the optimization of residual stress distribution is of great significance for titanium alloy machining.