| In the body,the flexible sheet part is its important component,Because of its insufficient stiffness,the traditional method of analyzing the deviation of rigidity assumption cannot meet the analysis demand.In order to improve the assembly quality of the car body,enterprises began to study the deviation analysis of The flexible sheet parts.In this dissertation,based on the internship units "body flexible a virtual matching" project Front wall lower plate assembly as the carrier,to carry out the analysis and research on the assembly deviation of flexible sheet parts.First of all,the dissertation analyses the factors affecting parts assembly,assembling deviation model is established by finite element method,and then through 3 DCS tolerance simulation software to verify this finite element model,finally,the product of tolerance optimization allocation.The main research work and achievements of this dissertation are as follows:(1)Introduced the Body size quality evaluation system,and analyzed the influencing factors of the assembly deviation of the flexible sheet parts,mainly including the dimensional deviation of the stamping process,the positioning error of the welding fixture,the deformation of the welding process and the error stacking caused by the welding structure.These factors provide a basis for the modeling of assembly deviation.This dissertation is the assembly deviation modeling analysis of the product based on the positioning deviation data of the fixture.(2)Based on welding assembly process and Positioning deviation data of welding fixture,Ansys Workbench software was used to establish the static analysis of finite element assembly deviation and the thermal field model based on the thermal elastic-plastic theory through the mesh division,load addition,boundary conditions and other operations on the Front wall lower plate assembly.The analysis results show that the welding deformation of parts is mainly affected by the positioning deviation of jig,and the effect of welding spot heat effect on the deformation of parts can be ignored.It provides an important basis for analyzing the assembly deviation of flexible sheet parts.(3)Based on computer aided tolerance design(CAT)technology,3DCS FEA Compliant Modeler flexible module was used to simulate the assembly of Front wall lower plate.Through FEA data loading and connection,3DCS FEA modeling,DTS measurement target establishment,tolerance addition,monte carlo simulation and other processes to obtain the simulation results of assembly deviation of Front wall lower plate.To comparison with the finite element analysis results,the correctness and accuracy of the finite element assembly deviation results based on the fixture positioning deviation data are verified.3DCS also analyzes the contribution value of the assembly deviation source,which provides a basis for the optimal allocation of tolerance.(4)The simulation results of welding assembly deviation of flexible parts show that the deformation caused by fixture positioning deviation has a great influence on assembly quality,which cannot be ignored in the optimization of tolerance allocation.The welding deformation factor is added to the assembly tolerance constraint condition.In view of the contradiction between quality and cost,the mathematical model of tolerance allocation optimization combining manufacturing cost function and quality loss function is established,and the genetic algorithm is used to complete the tolerance optimization.The optimization results show that not only the assembly quality is improved,but also the total tolerance cost is significantly reduced and the contradiction between quality and cost is effectively balanced. |
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