The Research On Modeling And Robust Fixture Design Of High-speed Train Sidewall

The sidewall is an important load-bearing part of the high speed train body,which is composed of large-scale hollow aluminum parts, and assembled inmulti-station. Fixture and parts deviations are passed, accumulated in the assemblyprocess, and eventually form the sidewall assembly deviation. Its deviation sizedirectly affects train body’s assembly quality and driving performance, such as lifeand traffic safety, being attached with great importance by enterprises. An assemblydeviation model based on rigid model assumptions provides an effective method toanalyze the sidewall dimensions deviation problems. Due to the Assemblyparticularity of the aluminum part, the deviation modeling method based on rigidbody assumptions are difficult to accurately simulate the sidewall’s assembly process.Studying the deformable sheet metal’s assembly deviation modeling method andconducting robust fixture design are keys to control the sidewall dimension precisionand to improve the quality of sidewall assembly.Firstly, this paper introduces the sidewall’s structure and its assembly process,with the analysis of the sidewall dimensions examination and assessment method,then summarizing the quality problems that exist in the current assembly process.Secondly, in view of the sidewall assembly craft characteristic, we propose the rigidand flexible assembly deviation coupled simulation analysis method, establishing theinfluence relational model of sidewall fixture factor and the assembly deviation, andthen develops the corresponding computational procedure. Assembly fixture robustdesign method for the stability of the sidewall quality is presented by combining withthe extraction of multiple design variables and quality index, to optimize the assemblyfixture locating scheme. Finally, through actual case analysis of the CRH3train bodysidewall, the validity of the deviation simulation model and the fixture robust designmethod which proposed has been confirmed.The main research of this paper as follows is:（1）High-speed train sidewall assembly process and its quality analysis According to the sidewall of the process features, we introduce sidewall’sstructure and its classification, and then detail its assembly process and performancerequirements. After analyzing the sidewall assembly fixture locating characteristicand simplifying its locating scheme, the positioning schemes for sidewall assemblyprocess in the opposite and positive assembly is given. In the end, we introduceassembly quality inspection and its evaluation method, and then summarizedimensions quality problems and the potential bias source factors which exist in thecurrent assembly process.(2) Assembly variation simulation modeling based on rigid-flexible couplingIn the light of the assembly process characteristic of the high-speed train sidewall,assembly variation simulation modeling based on rigid-flexible coupling has beenprovided, and its calculation programs are developed by MATLAB programminglanguage. In its assembly deviation modeling process, deterministic algorithm isemployed to calculate the assembly variation of the sidewall under the "3-2-1"positioning scheme, and further use the influence coefficient method to analyze theinfluence which the fixture factors exert on the assembly deviation when the sidewallwas in over-positioning. After stacking up, the sidewall assembly deviation transitiverelation expression can be obtained. Finally, the calculation of the side wall assemblyvariation simulation has been given by the sidewall assembly instance.(3) The sidewall assembly fixture robust design based on response surfaceHigh speed train sidewall assembly fixture robust design is conducted on thebasis of the sidewall flexible assembly deviation modeling method.Firstly, we introduce the high-speed train sidewall assembly fixture robust designbasic flow, mainly including parametric analysis of the sidewall assembly fixturerobust design&measuring point selection, experimental design, establishment andsolution of the target function. Secondly, on the basis of response surface model, wepresent the sidewall assembly fixture robust design method for the stability of thesidewall quality, to optimize the assembly fixture locating scheme. Finally, the robustdesign process has been expounded and the result of fixture robust optimization hasbeen displayed through the case of the assembly fixture design.(4) Case studies and verification of CRH3body sidewall assemblyOn the basis of assembling deviation modeling and assembly fixture robustdesign method, sidewall assembly deviation prediction and sidewall assembly fixturerobust design two cases are completed. Through the comparative analysis of calculation results with the measured data, it verifys the accuracy of the deviationmodel in this article. In addition, after the robust fixture design of the sidewall, thepassing rate and the quality stability have improved significantly.