Research On Finite Element Fast And Accurate Modeling Of A Kind Of Large Thin-walled Bar Assembly And Its Application In Body Structure Analysis

For the construction of finite element model of large thin-walled bar assembly,it is necessary to improve its modeling efficiency on the basis of guaranteeing the modeling precision.In order to solve the problem that the rigid connection relationship is difficult to be exactly established and the grid unit is difficult to automatically generate on different areas with different sizes,this paper studies the automatic segmentation of thin-walled bar connection area and the exact match of mesh nodes,and applies the accurate finite element model of bus frame to the lightweight design.The first chapter puts forward a kind of large-scale thin-walled bar assembly represented by vehicle body frame,and summarizes the structural characteristics and modeling difficulties of this kind of assembly.This paper summarizes the research status of finite element fast and accurate modeling,gird discrete point set matching and lightweight design of complex vehicle body,introduces the research content and its organizational frameworkThe second chapter proposes a connection area segmentation method of large-scale thin-walled bar assembly based on hardpoint mapping.By building the bounding box on the end face of bar,identify the connection surface of the end face of the bar.Based on multiple mapping on the boundary of the adjacent bar,automatically constructs the direct connection area of the bar and identifies the indirect connection area between the bars.On this basis,the grid unit is automatically and quickly generated to ensure the accuracy of the grid model while improve the modeling efficiency.In the third chapter,the point set matching method of line profile and surface area is proposed.In order to solve the problem of rigid connecting relationship in similar region,a point set matching method of line profile and surface area is proposed.According to the correspondence relationship of the faces and the correspondence relationship of the hard points,the nodes on the line profile will sequential match and the nodes on surface area will searching match,and the fast and precise construction of rigid connecting relationship of similar region is realized.Aiming at the problem of the construction of the rigid connecting relationship in non-similar area,considering the density of the mesh nodes,using different distanse constraints with sparse nodes and dense nodes,a method of node optimization matching based on improved genetic algorithm is proposed.On this basis,the rigid connecting relationship of the non-similar connection area is constructed automatically.In the fourth chapter,the stress distribution and deformation of the vehicle body frame under full load and empty load are analyzed.The influence of the skin structure on the modal performance of the vehicle body is compared and the modal performance of the vehicle body is evaluated.On the basis of static analysis and modal analysis,taking the thickness of part of the bars as optimization object,the first-order frequency maximum as the target,the full load maximum stress and body mass as the constraint,improves the vehicle body strength performance and dynamic performance while realizes the vehicle lightweight.The fifth chapter summarizes the research results of this paper,and prospects the future research work.