Fundamental Research On The Ultra-high Speed Grinding Of Nickel-based Superalloy With CFRP Wheels

Nickel-based superalloy with excellent high temperature strength,thermal stability and thermal fatigue resistance has been widely used in aerospace,aviation,shipbuilding fields.However,as a typically difficult-to-machine material,grinding efficiency and quality of nickel-based superalloys are low and thus the processing costs are high.In order to improve grinding performance of the material,modification of the material and renovation of the machining methods have been cumulatively developed.While ensuring a high service life of grinding wheel,how to further improve the machining efficiency and quality of nickel-based superalloy,are still the key point of grinding machining on nickel-based superalloy.In this paper,the concept of ultra-high speed grinding of nickel-based superalloy with carbon fiber reinforced polymer body wheel(called CFRP wheel for short)is proposed.On the theoretical level,based on the modeling and simulation of ultra-high speed grinding process of nickel-based superalloy,the material removal mechanism of ultra-high speed grinding was revealed.On the technical level,an ultra-high speed grinding test platform for nickel-based superalloy has been built by developing CFRP wheel and ultra-high speed grinding machine tool.On the experimental level,it concluded that ultra-high speed grinding technology can effectively improve the grinding performance of nickel-based superalloy by ultra-high speed grinding process experiments.The goal of improving the grinding efficiency and quality of the nickel-based superalloy meanwhile enhancing the life of grinding wheel has been achieved,which further promote the application of nickel-based superalloy material in the aerospace field.The main creative contents in this paper are as follows:(1)Based on the constitutive relation of materials the dynamic characteristics in chip formation process were discussed.Finite element simulation analysis of ultra-high speed grinding process was carried out for nickel-based superalloy.Through the study of chip morphology,equivalent stress,plastic strain and strain rate,grinding force and grinding force ratio,temperature and surface residual stress and strain,the influence of ultra-high speed grinding process on the removal mechanism was discussed combined with the speed effect and size effect.In theory,it was proved that ultra-high speed grinding can effectively improve the processing quality of nickel-based superalloy while improving material removal rate.(2)The advantages of CFRP wheel used in high-speed and ultra-high speed grinding were demonstrated from both theoretical and experimental point of view.The CFRP wheel for ultra-high speed grinding has been developed by optimizing the cross sectional shape of the wheel body,designing the CBN segments and checking the strength.The results of CFRP grinding wheel dynamic balance and safe rotation test showed that the designed CFRP wheel was reasonable and could be applied for ultra-high speed grinding experiments at the wheel speed300m/s.(3)On the basis of the overall structure of the grinding wheel spindle system,the spindle system of ultra-high speed grinding was developed by studying the static stiffness,the critical speed of spindle system under the gyroscopic effect,and the influence of the load on the dynamic characteristics of the spindle system.Based on the overall design scheme of the ultra-high speed grinding machine tool,the linear motor drive platform,coolant supply system and safety protection were designed,and ultimately the ultra-high speed grinding machine tool was developed.Through the performance test and analysis of the whole machine,it was proved that the designed machine tool was reasonable,and could be used for the ultra-high speed grinding at wheel speed higher than 300m/s.(4)Process experimental research of ultra-high speed grinding of nickel-based superalloy with CFRP wheel showed that by increasing the wheel speed and workpiece infeed speed,specific material removal rate of nickel-based superalloy was up to Q_w~'=8.4mm~3/(mm·s),the grinding ratio was increased by more than 50%,grinding surface roughness,surface profile and surface hardening were also significantly changed in a good trend,the surface roughness Ra was always under 0.4?m.All these demonstrate that ultra-high speed grinding process can observably improve the grinding status of nickel-based superalloy,and can further improve the grinding efficiency and quality meanwhile improving the grinding wheel life.