Study On Welding Residual Stress And Deformation Of Main Components Of Aluminum Alloy Vehicle

With the demand for "weight reduction and speed increase" of rail vehicles,aluminum alloy materials have been widely used,especially in high-speed motor car bodies.All kinds of car bodies are basically welded from aluminum profiles.Because aluminum alloy has a large thermal expansion coefficient and a high shrinkage rate,so its welding technology is difficult and the welding deformation is more difficult to control.If physical experiments are used to analyze the residual stress and deformation of the aluminum alloy car body,the accuracy will be high,but the cost is high and the time is long.With the continuous development of computer simulation technology,the accuracy of simulation has been very close to reality.Computer simulation method will greatly save human resources,material resources and financial resources in welding process analysis.In this paper,the welding residual stress and deformation of side wall of high-speed EMU body are studied by computer simulation technology combined with practical production experience.The main research contents in this paper included:Firstly,the heat source of the two typical joints was verified by thermo elasto plastic finite element method using the double ellipsoid heat source model.The simulation results were compared with the metallographic diagram obtained by the actual welding.And the metal fusion areas of the two are basically the same,thus the accuracy of the simulated heat source was confirmed.Secondly,a solid grid model was used to simulate and analyze the typical part of the side wall of the middle car on the high speed EMU based on the thermo elasto plastic method.Comparing the welding residual stress obtained by simulation with the measured value of X ray diffraction method,the trends of the two were basically the same,thus the accuracy of the simulation of the typical part was confirmed.Then,the influence of "various constraints" on the welding residual stress and deformation of typical parts were analyzed.Compared with other constraints,the square block fixture constraint was more in line with the actual welding condition.Meanwhile,the influence of three simulation methods of "thermo elasto plastic method","thermal cycle curve method" and "shrinkage force method" were applied to analyzed the simulation results.The research showed that the accuracy of the simulation results was thermo elasto plastic method,thermal cycle curve method,shrinkage force method.Finally,the welding deformation analysis of the overall model of the side wall shell element was carried out based on the inherent strain method.Comparing the overall deformation of the side wall obtained by the simulation calculation with the measured value,the measurement points with an error of less than 0.5 mm of the 30 deformation measurement points account for 83.33% of the total measurement points,and an error of less than 1 mm account for 100% of the total measurement points.Considering the inevitability of the simulation error,the simulation results of the overall model were considered to be accurate.Then,the influence of different "welding sequence","welding direction","point fixing method" and "number of fixtures" on the overall deformation of welding is analyzed.By analyzing the welding sequence and tack welding method,the welding deformation had a big influence: the maximum deformation of different welding sequences differed by 30.90%under ideal conditions.The maximum deformation of different point.fixing methods differed by 12.56%.The welding direction had an effect on the welding deformation,but the effect was small.Numbers of fixtures had an obvious effect on welding deformation,but if the fixture locations were selected properly,reducing the number of fixtures had little effect on welding deformation.The research in this paper can provide a reference for the actual production of the enterprise,optimizing the welding process and improving the welding quality.