Numerical Simulation Of High Speed Machining And Residual Stress Of 7055 Aluminum Alloy

7055 aluminum alloy proposing high strength,high fracture toughness,and excellent resistance to fatigue crack expansion are widely used in the manufacture of aircraft skins,truss and other monolithic components.In this paper,the numerical simulation of high-speed milling was carried out,and the influence of milling parameters and tool angle on the residual stress of 7055 aluminum alloy high-speed milling was studied.The Johnson-Cook constitutive equation of 7055 aluminum alloy was constructed by quasi-static tensile experiments and the split Hopkinson compression bar experiments at different temperatures and strain rates.The numerical simulation of the quasi-static tensile experiment was carried out,and the comparison between the simulation results and the experimental results showed that at the end of loading,the parallel section of the sample showed slight diameter shrinkage,and the stress distribution was roughly 45° to the axial direction,which had a good agreement with the experimental results.The numerical simulation of the two-dimensional milling process was carried out,and the three deformation regions of the milling process can be clearly seen from the stress nephogram,which was consistent with the theoretical part and verifies the rationality of the constitutive equation.The 3D high speed milling model of 7055 aluminum alloy could be simplified to a 2D orthogonal cutting model using the equivalent thickness method.The single factor simulation results demonstrated that milling speed,feed per tooth and milling depth were the key factors affecting the residual stress in high-speed milling.The influence sequence and optimization scheme of different cutting parameters on machining residual stress were obtained through orthogonal simulation experiment and range analysis,among which the optimized milling scheme(milling speed 2000 m/min,feed per tooth 0.1 mm/z,tool relief angle 4°,tool rake angle 16°,milling depth 10 mm,milling width 10 mm)could reduce the surface tensile residual stress,the optimized scheme(milling depth 10 mm,tool rake angle 16°,milling width 4 mm,feed per tooth 0.5 mm/z,milling speed 4000 m/min)could reduce the surface compressive residual stress.The optimization scheme was applied to the simulation of 7055 aluminum alloy high-speed milling,and the machining residual stress was effectively controlled.The effects of quenching residual stress on milling residual stress the initial stress of 7055 aluminum alloy were further studied.The results showed that the initial residual stress will lead the increase of milling residual stress.According to the law of single factor simulation experiment,this paper proposed to reduce the influence of initial residual stress by appropriately reducing the milling speed.Through the adjustment and simulation verification of the machining process optimization scheme mentioned above,the residual tensile stress and compressive stress of milling are reduced by 40.33%and 12.70%respectively.The results of the three-dimensional high-speed milling simulation of 7055 aluminum alloy showed that the change trend of milling residual stress in the direction perpendicular to the machined surface was the same whether there had initial residual stress or not,that was with the increase of the distance from the machined surface,residual tensile stress turned to residual compressive stress firstly,and finally fluctuated up and down at the compressive stress of 50 MPa.Most of the deformation of the workpiece in different areas is about ±0.2 mm.Compared with the trend and range of milling residual stress of homologous alloys in the literature,the reliability of the simulation results in this paper was verified.According to the results of three-dimensional orthogonal simulation experiment,an empirical formula for predicting the extreme value of residual stress in high-speed milling of 7055 aluminum alloy is constructed by using the method of multiple linear regression.