Simulation On Dissimilar Material FSW With Al And Mg Alloy For Rail Vehicles

Nowadays,the rail transit industry is developing rapidly,thus requirements for material properties of vehicle body are also constantly increasing.The composite structure of aluminum-magnesium(Al-Mg)alloy is gradually being widely adopted in high-speed rail transit industry.As a solid phase welding technology,Friction stir welding has incomparable advantages for welding of Al-Mg dissimilar alloys.Compared with welding of same material,the temperature field,stress and strain of different materials during welding process are much more complicated.Therefore,the research onto temperature field and residual state of Al-Mg dissimilar alloys holds great significance for FSW application in practical engineering.In this paper,the sequential thermal-mechanical coupling method was applied to study FSW temperature field and residual state of dissimilar materials through numerical simulation analysis.The main research contents include:Firstly,for butt welding of 6061-T6 aluminum alloy and AZ31B magnesium alloy,the distribution of welding temperature field was analyzed,and distribution of residual deformation and residual stress were studied through sequential thermal-mechanical coupling method.Under the condition that the numerical model is reasonable,effects of mechanical load and stirring head offset onto temperature field and residual state were discussed.Secondly,when it comes to lap welding of 5083 aluminum and AZ31B magnesium alloy,the temperature field and residual state were analyzed based on sequential thermal-mechanical coupling method.Based on verified rationality of numerical simulation method,effects of different process parameters onto temperature field and residual state were analyzed.In the meanwhile,effects of different length of stirring pin and lap widths onto temperature field and residual state were discussed.Finally,connection characteristics of welded joints and structural characteristics of profile inner cavity were taken into consideration,the welding finite element model of AZ31B magnesium and 6061 aluminum alloy box structure was established for rail vehicle profile structure.Based on actual situation,the welding scheme was determined,and the welding method with the upper and lower welds was adopted.Influence of joint structural material onto residual stress distribution and residual deformation was also compared.The analysis of temperature field and residual state for friction stir welding with Al-Mg dissimilar alloys can be used to study the performance of friction stir welding joints and optimize the process parameters,so as to improve the welding quality.