Study On Experiment And Numerical Simulation Of Miniature Gear Manufactured By Magnetic Pulse High-speed Bulk Forming Process

Magnetic pulse high speed bulk forming is a metal processing method based on electromagnetic force loading,which can be used for bulk forming of metal block,bar or thick plate.It has the advantages of high forming speed,environmental protection of energy source and easy automatic control,so it is a potential green manufacturing process.At present,the research and application of magnetic pulse forming technology mainly focus on sheet metal,but it is rarely used in the manufacture of parts with the same three-dimensional size.This paper has made a preliminary exploration on the high speed bulk forming process of magnetic pulse.The free upsetting section of miniature pure copper cylinder is analyzed from the aspects of metallographic structure,stress-strain distribution,hardness distribution and adiabatic temperature rise,and the magnetic pulse bulk forming technology is applied to the forging of miniature gears.The crystal plastic finite element method(CPFEM)is used to simulate the micro plastic strain process of pure copper on the grain scale,which provides a scientific reference for the subsequent miniaturization of mini gears.Firstly,some miniature T2 pure copper samples with a diameter of8 mm were upset by magnetic pulse free upsetting with different process parameters.The microstructure,stress-strain distribution,hardness distribution and adiabatic temperature rise of the sample after high-speed compression deformation were studied.The results show that the cross section of the specimen is drum shaped,the plastic deformation is mainly concentrated in the diagonal X-shaped region,and the strain hardening effect and adiabatic temperature rise effect are obvious.The finite element model of high-speed free upsetting of cylindrical magnetic pulse is established,and the simulation results are compared with the experimental results.The results show that the relative error between the simulation results of the finite element model and the experimental results is less than5%,and the finite element simulation results are more accurate and reliable.Secondly,a set of miniature gear mould suitable for high speed magnetic pulse bulk forming is designed.The cylinder is forged by the magnetic pulse volume forming technology.The results show that the mini gear with complete shape can be obtained under 12 k J discharge energy.Compared with the quasi-static forming gear,the results show that the filling performance of the upper end of the high-speed forming gear is better due to the inertia filling effect and friction.The strain rate hardening effect in high-speed forming leads to grain fragmentation and dislocation density increase,which leads to higher hardness than that in quasi-static formingFinally,aiming at the above free upsetting and die forging process,the plastic deformation process of pure copper under the condition of micro forming is simulated and analyzed by using the crystal plastic finite element method.The results show that the finite element simulation of crystal plasticity can reflect the deformation behavior of the material in micro forming;The simulation results show that the deformation inhomogeneity of polycrystalline pure copper can be improved by increasing friction coefficient,and the maximum equivalent stress value increases with the increase of friction coefficient.