Modeling And Simulation Of Micro-milling Burr And Optimization Of Process Based On Strain Gradient Theory

With the development of production miniaturization and integration trends,the demand for micro-miniature parts and products is increasing.Compared with processing technology of other micro-miniature parts,micro-milling technology has the characteristics of wide application range,high processing efficiency and can process complex structural parts,and has been widely used in actual production.However,when using this technology to process some materials with good plasticity,defects such as burrs are generated,which seriously affects the performance of micro-miniature products.Therefore,this paper uses the combination of finite element simulation and experiment to study the factors which affect the micro-milling top burr size of oxygen-free copper material,and optimize the factors to achieve the purpose of suppressing burr.The minimum cutting thickness and size effect existing in the micro-milling process are studied,which lays a foundation for the correction of the constitutive model.Through the two-dimensional orthogonal cutting simulation,it is found that the traditional Johnson-Cook constitutive model can not accurately reflect the size effect of the workpiece material,and it needs to be modified for the simulation of the micromilling process.The modified constitutive model is applied to Abaqus simulation using the user material subroutine Vumat,and the correctness of the Vumat subroutine and the modified Johnson-Cook constitutive model is verified by a single mesh model,a two-dimensional micro-cutting model and a three-dimensional micro-milling model.Through the traditional three-dimensional micro-groove milling simulation,the effect of the size effect of the blunt radius on the size of the top burr is studied.The simulation model considering the size effect of workpiece material is used to simulate the effect of workpiece material size effect and milling parameters on the burr size of the micro-groove and compare with the experimental results.It is more accurate to verify the simulation of considering the material size effect of the workpiece.The simulation model considering the size effect of the workpiece material is used to simulate the influence of the geometry parameters of the micro-milling cutter on the top burr size,and then the structural parameters of the micro-milling cutter are optimized.Based on the results of the orthogonal experiment of microgroove milling,the influence of milling parameters on the size of the top burr is studied.The prediction model of the top burr size is established and verified by experiments.Then,using the top burr size prediction model,in order to achieve the two-objective optimization of the top burr size and the workpiece material removal rate,the process parameters are optimized based on the NSGA-II multi-objective optimization algorithm.The effect of radial milling depth on the size of the top burr is studied by experimental method,and the process parameters when processing the microstructure are optimized.The characteristic structure is processed by using the above optimized process parameters,and the correctness of the process parameter optimization is verified.