Distortion Control And Process With Hot-cold Source During Aero Aluminum MIG Welding

For aluminum alloy plates,especially thin structures,large residual stress and distortionduring welding are easily occurred.Combined with numerical simulation and experiment in this thesis,research on the control of aluminum alloy welding stress and deformation was conducted.Trailing intensive cooling,dynamic auxiliary heating and the combination of heat-cold source process were mainly discussed.Firstly,the MIG welding model of the thin aluminum alloy was established by the finite element software MSC.Marc,and the reliability of the model was verified by temperature measurement.Based on the welding model,the simulation of trailing intensive cooling(TIC)was carried out to study the influence of different cooling parameters on the welding stress and strain during the welding process.The results showed that the cooling effect was heightened with decreasing cooling distance.The increase of cooling intense was beneficial to reduce the residual tensile stress.Compared with the cooling distance or cooling intense,the length of cooling zone owned a less cooling effect.In this thesis,the optimum cooling zone width of 40 mm was attained according to the width of tensile stress zone perpendicular to welding line.Secondly,the mechanism of dynamic auxiliary heating deformation control was studied,by researching the influence of dynamic auxiliary heating source(DAHS)position parameters on the welding longitudinal residual stress.When the separation of the two auxiliary heat sources was increased,the reduced extent of compressive stress near the weld was reduced.The change of the longitudinal distance between the behind DAHS and the welding torch had a little influence on the residual stress of weld.For the front DAHS,the compression stress near the weld was obviously reduced with the decrease of longitudinal distance.When the DAHS-TIC conditions were used together,the reduced effect of welding residual stress was further heightenedFinally,based on the above-mentioned simulation results and the welding devices,the parameters of TIC and DAHS used in the experiments were confirmed,and then the experiments about residual stress and distortion were performed.The experimental results showed that with decreasing the cooling distance of TIC,the reduction of welding distortion was increased.Compared to the behind DAHS,the front DAHS had a better reduction influence on welding distortion.For DAHS,TIC and DAHS-TIC conditions,the welding distortions were respectively reduced by 34%?48% and 58%.Therefore,the DAHS-TIC condition could attain a better influence on the control of welding distortion,which verified the above-mentioned residual stress results by simulation.Moreover,the measurement results of residual stress in this thesis also verified the reliability of simulation.