Study On Fixture Optimal Design Method Of High Speed Train Aluminum Alloy Body

As the main load-bearing part of high-speed train body,the sidewall is welded from multiple extruded aluminum alloy panels with complex cross-section structure.Because of the aluminum alloy material characteristics and the sidewall structural characteristics,the sidewall is prone to large deformation during the welding process.It is not only related to whether it can be well assembled with other body parts,but also affects the safety and reliability of the whole life cycle of the high-speed train.To eliminate welding deformation,the welds need to be heated and repaired with flame after the welding,which not only increases the workload,but also reduces the quality of welds.The welding quality of the sidewall is mainly guaranteed by fixtures.A reasonable arrangement of welding fixtures for the sidewall can reduce the deformation caused by welding,and greatly improve the welding quality of the sidewall.Therefore,this thesis took the sidewall fixture as the research object,and carried out the optimization design research of the locating parameters of the sidewall fixture,which provided guidance for the welding deformation prediction and control of the high-speed train body in production.The specific researeh content of this thesis includes the following four parts:(1)Verification of shell element analysis model based on aluminum alloy sheet welding experiment.Because the sidewall model is large and the structure is complex,it is difficult to directly perform numerical simulation of welding deformation,the accuracy of shell element used in the sheet welding simulation was verified by aluminum alloy sheet welding experiment.Firstly,two different thickness of aluminum alloy sheet welding experiment were carried out and the welding deformation results were measured.Then,established the finite element model with solid element and shell element respectively for welding deformation simulation.The accuracy of thermal elastic-plastic finite element analysis method and shell element model used in welding numerical simulation of aluminum alloy sheet was determined by comparing the two results.Which provided a foundation for the shell element to be used in the numerical simulation of sidewall welding.(2)Finite element model establishment and verification of sidewallThe sidewall shell element model was established and the welding simulation results were analyzed.Firstly,the sidewall model was intercepted and simplified,the sidewall shell element model was established.The process of welding deformation analysis by macro file was sorted out.Then,the simulation results of welding temperature field and welding deformation were analyzed.According to the sidewall deformation detection process and the measurement point location distribution,the simulation analysis results were compared with the measured data in production,which verified the accuracy of the shell element finite element model.Through the analysis of welding deformation,the average deformation in the normal direction of each measuring point of the sidewall model was selected as the evaluation index to carry out the subsequent analysis of fixture locating parameters.(3)Optimal design of sidewall fixture locating parameters for minimum deformationControlling the welding deformation of the sidewall is the key to the optimization design of the side wall fixture.Therefore,the fixture locating parameters of the sidewall is optimized by taking the minimum deformation of the sidewall as the optimization goal.Firstly,based on the consistency of fixture locating parameters,the distance between the fixture locating point and the weld,and the distance between the two sets of fixtures were optimized.Then,based on the difference of fixture locating parameters,a second-order polynomial response surface model was established through the central composite design to optimize fixture locating parameters.The optimized fixture locating layout has a significant effect on the suppression of welding deformation of the sidewall.(4)Optimal design of sidewall fixture locating parameters for robustnessIn order to reduce the influence of fixture locating deviation on sidewall welding quality,the Taguchi method and the dual response surface method were carried out respectively for the fixture locating parameters robust design.Firstly,the concept of robust design and the robust design process for the sidewall fixture were introduced.Secondly,based on orthogonal design by inside and outside array design,the Taguchi method was used to design the robust parameters,and the locating parameters of sidewall fixtures were optimized according to the signal-to-noise ratio,and the locating parameters of the sidewall fixture were optimized based on the signal-to-noise ratio.Then,a comprehensive robust design model of sidewall fixture locating parameters was established and optimized by using the dual response surface robust design method.Finally,through the comparison and analysis of the two optimization methods,it was concluded that the sidewall fixture robust parameter design based on the dual response surface method is better.