Research On The Prediction And Suppression Method Of Cutting Deformation Of Thin-walled Parts With Weak Rigidity Of Aviation Aluminum Alloy

Aeronautical aluminum alloys are widely used in aerospace due to their lightweight and high specific strength.The improvement of the aircraft’s comprehensive performance puts forward more stringent requirements for the high-precision manufacturing of aeronautical workpieces.The suppression and reduction of the deformation of aeronautical thin-walled workpieces is always a challenge to be solved in the manufacturing field.In particular,the issue of machining deformation of large aeronautical thin-walled workpieces caused by residual stress becomes increasingly prominent.It seriously affects the production efficiency and cost of aerospace products.Machining deformation is a combination of multiple factors,among which the residual stress is the critical factor affecting the workpiece deformation.For a thin-walled workpiece,the residual stress caused by machining has a significant influence on its deformation.Therefore,this paper systematically studied the deformation law of 7075 aluminum alloy workpieces under the influence of initial and milling residual stress by combining theoretical analysis,finite element modeling,and experiment.An innovative process using Nanosecond Laser micro-milling technology to effectively suppress the deformation of weakly rigid thin-walled parts is proposed.The main research contents and findings are as follows.(1)Cutting residual stresses were modeled analytically,based on two-dimensional orthogonal cutting.According to the analytical model,the multivariate decoupling method was used to analyze the sensitivity of each essential variable to the output and perform the traceability analysis of cutting temperature and residual stress.Thus,the influence mechanism of residual stress was revealed.(2)The milling processing experiment of 7075 aluminum alloy was carried out by the orthogonal test method,and the influence law of the milling process parameters on the residual stress was studied.A quantitative calculation model between residual stress and milling parameters under end milling and side milling were established by regression analysis,thereby revealing the sensitivity coefficients of each milling parameter to residual stress.A genetic algorithm was used to optimize the neural network based on the experimental data,and a prediction model for the residual stress of milling machining was established.(3)The bending deformation mechanisms of typical workpieces under the influence of initial and milling residual stresses were analyzed based on elastic-plastic sheet bending theory.It was pointed out that the influence of residual stress on the bending deformation of the workpiece can be equivalent to the influence of external load moment on the bending deformation.A semi-analytical model was established for "residual stress-bending deformation" of the workpieces such as plate,frame,cantilever,and T-shape.The cutting experiments showed that the proposed model has high prediction accuracy.The prediction model reveals the law of workpiece stress distribution and deformation,providing a quantitative calculation tool for production guidance.For weak rigid thin-walled parts,the theoretical model presents that the contribution rate of milling residual stress to the deformation exceeds50%.It cannot be ignored.Two machining solutions were proposed to suppress the thin-walled workpiece deformation.The first is to adjust the milling parameters to obtain different milling residual stresses on the upper and lower surfaces.The second is to change the residual stress of the surface layer after milling.(4)The influence of different laser processing parameters on the workpiece surface quality was analyzed based on the orthogonal experiment of nano-laser micro-milling.The parameters include scan speed,laser power,repetition rate,and scan number.A prediction model of surface roughness was established based on the experimental data.The influence mechanism of nano-laser micro-milling on surface residual stress was analyzed.And the influence law of various process parameters on residual stress was revealed.An innovative process solution was proposed that laser micro-milling is used to control the deformation of low-stiffness thin-walled workpieces.A dual objective optimization based on deformation and surface quality was implemented.The experiments supported that the workpiece deformation obtained by the optimized nanosecond laser micromilling process scheme was reduced by 33.6%.A significant effect is proved using nano-laser micro-milling to reduce the milling processing deformation of low-stiffness thin-walled workpieces.The findings has important practical value in engineering.