Finite Element Simulation Study On The Process Of Friction Stir Welding Of7022Aluminum Alloy

As a new solid-state welding method, friction stir welding with many advantages in the welding ofaluminum and its alloy has been widely applied in aerospace, etc. In this paper, high-strengthaluminum alloy7022was regarded as the welded object, and its friction stir welding process finiteelement simulation research was carried out on the basis of relevant experiments, the main researchwork and achievements as follows:1. Based on the division of friction stir welding process and the built heat input modelcorrespondingly, a FEM model of temperature field was built up. Temperature distributions of theeach stage were obtained by the simulation analysis on the fully welding process. By comparing theresults of FEM model and experimental results, the heat input model and the temperature model wereverified. And on this basis, the influence of preheating on the welding process was also analyzed.2. Based on computational fluid dynamics theory, a coupled flow-thermal finite elementmodel of the process of friction stir welding was built, and both the welding process heat transfer andmetal plastic flow simulation analysis was carried out at the same time, and the three-dimensionalflow field and temperature filed of viscoplastic metal were obtained. Results showed, compared withwelding speed of stir tool, the effect of the rotational speed to promote plastic metal flow is moreobviously. At the same time, compared to single flow filed model, the coupled flow-thermal modelshowed plastic metal flowed more fully. Finally the macrostructure of the joint with the materialdeformation lines of advancing side and retreating side was observed, and simulation result of plasticflow was verified indirectly.3. Based on the research on temperature field, the coupled thermal-mechanical simulationanalysis on the welding process was carried out, and the welding stress field and stress variation curvewere obtained. Moreover, the general rule of the residual stress and deformation after welded werealso obtained:①Residual stress mainly concentrated in the weld, and the longitudinal residual stresswas relative big. In the vertical direction of weld, the longitudinal residual stress distribution curvewas of the shape of M, and along the weld direction, the longitudinal residual stress distribution curvewas of the shape of parabola;②The trend of welding deformation was mainly angle deformation,that is the Z direction deformation along the width direction is more apparent, the main trend isdownward concave.4. The simulation analysis on the welding stress and deformation of aluminum alloy sheet with a hole was carried out, and the welding sequences were also optimized. Results showed that sequence2welded from both sides to the middle was superior to both the sequence1welded from middle to theboth sides and the sequence3welded from left to right.