Surface Stress Release And Control Of Al Alloy Thin-walled Frame Under VSR

High strength aluminum alloy thin-walled frame has the characteristics of high strength and light weight,which is widely used in aircraft structural parts.The manufacturing and processing of thin-walled frame will bring a lot of residual stress to the interior of share parts,which makes the size of frame unstable.In this paper,VSR(Vibration Stress Relief)was used to reduce residual stress in ferrous metal field,7075 aluminum alloy thin-walled frame is selected as the object to study the release and homogenization of surface residual stress,the finite element simulation model is established,and its mechanism is explained from macro and micro perspectives.The research results not only have practical engineering application value for the stress and deformation control of thin-walled frame after preparation,but also have important reference value for the VSR research in other directions.The main research work is as follows:1.The simulation model of platform VSR is establishedANSYS was used to simulate the aging process.The relationship between the vibration mode and the excitation frequency was obtained from the modal analysis The resonance area was found and the experimental parameters are determined.The characteristics of surface stress variation were obtained by harmonic response analysis,which provides a way to customize the experimental scheme of homogenizing stress2.The surface stress was released and homogenized by vibration aging experiment and position overlapping aging.The aging experiment of the thin-walled frame was carried out by using the platform VSR.After the stress analysis by XRD(X-ray Diffraction),it was found that the surface stress was relaxed to a certain extent,and the release rate ranged from 9%to 33%.Based on the simulation results,the position overlap method is put forward.The results show that the position overlap method can effectively homogenize the surface stress without continuously reducing the surface stress intensity,and the optimal nonuniformity can be reduced to 10%.3.The mechanism of VSR is revealed from macroscopic and microcosmic aspectsBased on Bauschinger effect and grain deformation,this paper summarizes the macro and micro mechanism of VSR to reduce residual stress.At the same time,EBSD(Electron Backscattered Diffraction)analysis shows that the grains are refined,the recrystallized grains increased by 9%,and the surface properties of the material are improved.Through the analysis of deformation and hardness,it is found that the microhardness after VSR is increased by 10%-17%without destroying the dimensional accuracy.It shows that VSR has a positive effect on improving the surface characteristics of components,and can stabilize the structure size.