Investigation On The Mechanism And Method Of Rolling Distortion Correcting For Aeronautical Beam Components Made Of Aluminum Alloy

Due to the coupling effect of various factors in the machining processes,aluminum alloy components what are wildly used in modern aircraft are suffering serious machining distortion problems in varying degrees and different forms.Distortion correction is an effective approach to ensure the dimensional accuracy of aeronautical components and to achieve a stress-free assembly of aircraft.Noticeably,traditional correction methods such as anti-distortion correction will inevitably introduce surface tensile stress on the surface,which has adverse effects on the fatigue life of the workpiece.Rolling distortion correction has been draw increasing attention and been applied in the aviation industry,which can introduce surface compressive stress.It is an effective distortion correction method to obtain the size accuracy of large length-to-width ratio thin-walled structures.At the same time,the fatigue life of the workpiece can be improved through the introduction of surface compressive stresses.However,mostly of the rolling distortion correction currently depends on the workers' experience and trial and error method,lacking of effective correction theory,operating procedures,and process system guidance.Therefore,the stability of correcting quality is poor and the manufacturing quality and efficiency of aeronautical components is seriously restricted.Consequently,the correcting theory,method and technological process to correct the overall distortion of the aeronautical components are investigated based on key scientific problems of the micro plastic deformation and deformation coordinative induced by rolling.The aluminum alloy 7050-T7451 was used as the targeted material to study the physical and mechanical properties in the rolling process.First,the bilateral rolling experiments on thin-walled structures were carried out,the evolution of microstructure structure was revealed,and the formation mechanism of rolling residual stress field was clarified.Then,the characteristics of surface morphology and microhardness changes was analyzed by the rheological behavior of the material to obtain the influence of rolling operation on the surface integrity.A finite element model of bilateral rolling process was established by using ABAQUS software.The model was experimentally verified from the perspective of strain and stress.At the end,the evolution of strain,stress,and distortion during the rolling and the clamping releasing processes were analyzed.It was found that the microplastic deformation caused by rolling is the intrinsic factor in the shape change of the aeronautical components.Based on the study of the rolling distortion features of simple structures,the rolling distortion correction of complex structures was then studied.The cross-section characteristics of beam components are firstly analyzed,and the T-shaped and U-shaped cross-section are selected and characterized for rolling distortion correction.Then,the influence of rolling parameters on the feature of rolling distortion for a typical T-shaped structure was obtained by the finite element method(FEM).On this basis,an equivalent moment method was used to analyze the influence of rolling on the bending distortion of the structural parts,and a theoretical model of equivalent moment,rolling parameters and workpiece structure parameters was established.Finally,the equivalent moment method is used to predict the correction load for rolling distortion correction process.The feasibility and effectiveness of the method was verified by rolling correction experiments in which the distortion of T-shaped workpieces was reduced by 73.6%.In order to realize the load prediction for rolling correction of complex beam components,the relationship between the strain energy contained in the bending distorted workpiece and the external force work in the rolling process was established based on the principle of energy balance.The external energy input needed for correcting the workpiece was obtained,and then the correction torque required was also obtained to realize the prediction of the rolling correction load.By using the direct stress method,the simulation of the rolling distortion correction of complex structural parts was realized,and a collaborative simulation environment of machining distortion-rolling correction was established to achieve a rapid evaluation of the predicted accuracy of the rolling correction load.The load prediction method was validated by a three-frame beam component.The distortion obtained from the simulation was reduced from 0.321 mm to 0.018 mm by 94.5%,and the experimental result was reduced from 0.333 mm to 0.060 mm by 82.0%.According to the distortion characteristics of beams with both structural and stress discontinuity,a segmented correction theory was proposed which mainly based on the curvature characteristics of the deflection curve,as well as the workpiece structure and rolling process requirements.The correction strategy involved in the rolling distortion correction process was discussed based on an eight-frame beam component,such as correction segment,load prediction and correction sequence.The distortion of the workpiece under the "alternative correction" sequence was analyzed with emphasis,and then the correction strategy for long beam components was optimized,which can significantly improve the correction efficiency while ensuring quality.