Study On The Residual State Of Friction Stir Welding Of Rail Vehicle Profiles

With the rapid development of rail transportation equipment industry,a large number of aluminum profiles have been applied to rail vehicles.Because of its low melting point and complex structure,aluminum alloy has some defects in traditional welding seam.As a solid phase joining technology,friction stir welding(FSW)has great advantages over traditional welding,especially for aluminum alloy and other materials.In recent years,friction stir welding has been gradually adopted in the welding of rail vehicles.Therefore,it is necessary to study the residual stress and residual deformation of the friction stir welding of rail vehicles for friction stir welding in practical engineering.Several key problems in numerical simulation of friction stir welding are studied in this paper.Through numerical simulation,the residual state of welded rail profiles after welding is thoroughly discussed.The main contents are as follows:The temperature field of friction stir welding is analyzed,and the influence of the size of the numerical model is studied based on the temperature field analysis results.Under the premise that the temperature field variation rule is reasonable,considering the different plate thickness and rotational speed,reasonable suggestions for the size of the numerical model of the temperature field are put forward.Based on the temperature field analysis,the influence of different meshes on the temperature field is explored,and a reasonable mesh generation scheme is proposed.The residual stress and residual deformation of the aluminum alloy plate butt welding were simulated and calculated by the sequential thermal coupling method,and the rationality of the finite element model and the feasibility of the numerical simulation method were verified.The influence of release point selection,preheating time,heat distribution of shaft shoulder and stirred needle,and shoulder shoulder size on residual stress were investigated.The distribution characteristics of residual stress under different material models are discussed.In view of the connecting characteristics of the track vehicle profiles and the structure characteristics of the inner cavity of the profile,the finite element model of two lap welds on the panels is established for three different sections of the joint structure of the box,double V and box-V profiles respectively.According to the actual situation,the welding plan of the weld is determined.The AL6005A-T6 and AL6082-T6 aluminum profile materials were taken into account,and the post weld residual state of three kinds of profile connection structures was simulated by sequential thermal mechanical coupling method.The variation of residual stress and residual deformation of the three sections of connecting structures under different material conditions are compared and analyzed,and the influence of the stiffeners on the residual stress and residual deformation is discussed.For the connection structure of double V profile,the finite element model of the connection structure of the 60°,90° and 120° degree angle is established.The residual state of AL6005A-T6 aluminum profile was simulated by the thermal coupling method,and the influence of the angle of different stiffeners on the residual stress and residual deformation after welding was discussed.