Research On The Assembly Variation Prediction Of The High-Speed Train Body Considering Welding Deformation

With the rapid development of high-speed railway technology,the traveling speed of trains is getting higher and higher.In the course of the rapid transit of the train,the safety of the train and the ride comfort can be significantly affected due to the heavy load impact.As the train body is the main bearing structure of the high-speed train,the quality of its manufacturing will directly affect the development of the high-speed train industry.The highspeed train body is welded by many extruded aluminum alloy profiles.On the one hand,the extruded profile itself has certain manufacturing deviation.On the other hand,in the process of parts welding,the parts are welded and deformed due to the intense heat absorption and exotherm.In addition,the positioning deviation will be introduced during the assembly process.This leads to the difficulty in controlling the final manufacturing quality and assembly accuracy of the train body,which is a problem that must be solved in the further development of the high-speed train industry.This paper aims at predicting the assembly deviation of the key dimensions of the high-speed train,and the numerical simulation prediction method for welding deformation of large structure is studied.Then,the influence of various deviation sources such as welding deformation,part deviation and positioning deviation on the final assembly quality of the train body is considered and analysed.Finally,the accuracy and feasibility of the method are verified by comparing with the measured data.This method can provide guidance for part size design,positioning mode selection and welding process planning of the train body during the design and development stage.The specific research contents of this paper include the following three parts:(1)Thermal elastic-plastic analysis of the sidewall,roof and underframe.Based on the "local-global" method,thermal elastic-plastic finite element method was used to study the influence of transient temperature field on the distribution of the residual plastic strain of three main sub-assemblies.And the applicability of double ellipsoid heat source in the numerical simulation of aluminum alloy welding is pointed out.Through the analysis of the simulation results,the residual plastic strain is concentrated in the weld and its heataffected area.This is due to the high temperature and temperature gradient in the region during welding process,which results in the internal stress caused by uneven temperature distribution meets the material yield strength.Then the residual plastic strain is produced and the deformation of welding structure is caused.(2)Welding deformation analysis of the sidewall,roof and underframe.According to the distribution of the residual plastic strain of the welding seam of the three sub-assemblies of the high-speed train,the transverse and longitudinal inherent strain was extracted.Then,the finite element model of the global structure is established by referring to the welding process of sidewall,roof and underframe.Next,the inherent strain is converted into the anisotropic thermal expansion coefficient of the material near the welding bead.Finally,the prediction of the welding deformation of the sidewall,roof and underframe is realized by the elastic calculation.Through the analysis of the simulation results,it is found that the height of the side wall,the width of the roof and the width of the underframe get certain shrinkage after welding.The good agreement of measured data and simulation results verifies the feasibility and accuracy of the method of inherent strain to predict welding deformation.(3)Analysis of assembly deviation of key dimensions of high-speed train.In order to predict the height and width of the train body,the model of assembly variation based on rigid consumption is built according to positioning strategy and assembly sequence by use of VisVSA.Then,the results of assembly variation of sidewall height,roof width and underframe width are modified by mean shift to consider the welding deformation.Next,the modified result is used as the deviation input of train body assembly,and the train body assembly process is simulated with the factors such as part tolerance,fixture positioning deviation and welding deformation.Finally,the feasibility of this method is verified by the comparison between the simulation results and the actual measured data.