Study On Cutting Simulation And Microstructure Deformation Mechanism Of Ni-base Superalloy Polycrystalline Materials

Inconel718 is widely used in aerospace,electric power and many other fields because of its excellent thermal stability,excellent fatigue resistance,corrosion resistance and oxidation resistance.However,the poor thermal conductivity and complex crystal structure of Inconel718 make the tool chip interface temperature high,the cutting force large and fluctuating,and the machined surface produces excessive residual deformation.The existing traditional homogenization models are based on the macro analysis of homogenization.It can't well explain the blocking effect of grain size and grain boundary on dislocation slip in the cutting process.It can't well explain the blocking effect of grain size and grain boundary on dislocation slip,crack initiation and propagation and residual stress distribution in the cutting process.Therefore,based on the polycrystalline model with grain boundary,the cutting mechanism of high-speed cutting Inconel718 is studied in this paper.Through the Split Hopkinson Pressure Bar experiment(SHPB).The thermal deformation behavior of Inconel718 at high strain rate and high temperature was studied.The effects of temperature and strain rate on material flow stress are analyzed.According to the size of different grain size and containing~?/~?relative dislocation pile-up.The dislocation pile-up theory is introduced into the traditional JC constitutive model.In the process of finite element cutting modeling and simulation,the characteristic parameters of grain size and the effect of grain size can be well characterized.By comparing the simulation and experimental results,and based on correlation analysis and error analysis,the correlation between the simulation value and experimental value of the modified constitutive model is R=0.97981,and the average relative error is only 3.72%.The improved constitutive model can accurately predict the flow stress of Inconel718 at high strain rate and high temperature.The cutting deformation mechanism of Inconel718 was studied from the microscopic point of view.The chip root metallographic specimen was extracted by means of explosive rapid cutting tool.The high speed cutting test of Inconel718 was carried out by changing different cutting parameters.The experimental data of cutting force and temperature are obtained.Through the secondary development of ABAQUS,VUMAT subroutine was written to introduce geometric must dislocations to grain boundaries.A multi-crystal two-dimensional cutting simulation model is established.The chip formation process is simulated and analyzed.Combined with the comparison and analysis of experimental results,the influences of cutting force,cutting temperature and geometrical dislocation on the cutting deformation mechanism and material removal mechanism are further revealed.The microstructure of polycrystalline material has a certain influence on cutting process.The effects of grain size,dislocation density and grain boundary on cutting force,cutting temperature and residual stress are discussed.The residual stress of high temperature and high strain rate cutting strip is analyzed.The formation mechanism and distribution of residual stress on machined surface were studied by establishing the cutting model of separate Inconel718 polycrystal,and the effects of grain size and cutting parameters on residual stress were obtained.It provides theoretical basis and reference for optimizing cutting parameters and improving machined surface quality.