Research On The Theory And Method Of Modular Concept Design Of Automotive Body

The research and development of automotive body is a very complex work,usually divided into two design stages: conceptual design stage and detailed design stage.In the conceptual design stage,it requires early prediction of the static,dynamic and crashworthiness characteristics of the body structure,which can provide powerful data support for the detailed design of the body in the later stage,and can effectively reduce the manufacturing risk and design time.As a result,in the traditional body structure design process,as the limitation of body structure data in the conceptual design stage,it is usually impossible to carry out fast and effective structural performance verification.Therefore,the vehicle body reverse design based on competitive models and engineers' experience has become the mainstream design method in automotive manufacturing enterprises,which leads to the disadvantages of heavy workload,low reliability and long cycle of body structure design.Therefore,it is crucial to find a forward design method basded on structural parameters,global optimization and structural performance in the conceptual design stage.The purpose of this paper is to realize the effectively modular concept design of automotive body,and the theory and method of the body modular concept design are deeply studied.A simplified modular body model is used as the benchmark,according to the structural characteristics of the body model,a feasible modular stiffness chain model of the body structure is established by combining the structural mechanics analysis method,and the effect of the flexibility of the automotive body joint is taken into consideration,the joint surrogate model is constructed.Then a new structural optimization algorithm based on sensitivity analysis is proposed for the global optimization of the body structure under different load conditions,and the lightweight is realized.Lastly,in order to promote the modular concept design of body model,a corresponding software system of body structure design is developed.The main contents of this paper are as follows:(1)The stiffness chain model of modular automotive body structure in the conceptual design stage is established to realize the performance analysis and optimization of the global body model.Based on the geometric data of simplified modular vehicle body,the method of reverberation ray matrix and the genetic algorithm are used as basic analysis and optimization tools respectively,the real bdoy model is converted into a spatial wireframe model composed of semi-rigid beam element modules,and the static and dynamic performance analysis and overall structure optimization of the body are realized.The structural optimization is based on the structural performance analysis,the structural performance analysis is to achieve structural optimization,the two complement each other and establish the stiffness chain model of modular automotive body structure,which provides a feasible tool for the structural performance analysis and optimization of the global body structure.(2)An automotive body joint surrogate model capable of reflecting the flexibility characteristics is constructed to improve the accuracy of the structural performance analysis of the body conceptual model.According to the flexibility characteristics of body joints,a lot of real joint samples are extracted by Latin hypercube sampling,and the geometric data of the samples are taken as independent variables and the stiffness analysis data as dependent variables,then a surrogate model of body joint with three tension springs and three torsion springs is constructed by the response surface method.The joint surrogate model is introduced into the body stiffness chain model,so that the joint flexibility attribute can be accurately utilized in the structural performance analysis and optimization calculation process of the body model at each time,which effectively improves the static and dynamic performance analysis precision of the body-in-white model and lays a foundation for establishing a feasible stiffness chain model.At the same time,it also provides a new idea for the study of the performance of body joint.(3)A new lightweight optimization method of the automotive body model based on sensitivity analysis is proposed to improve the effectiveness of optimization results.With the goal of lightweight design of the vehicle body,the influence factors of body-in-white structure on lightweight design are analyzed.Based on the stiffness chain model,the method of reverberation ray matrix and the finite difference method are combined to calculate the influence degree of the design variables contained in each beam element on the structural performance of the vehicle body model,and then the sensitivity values of beam element under each loading condition are obtained.According to the sensitivity values,the optimization direction of each beam element in the lightweight design of automotive body is determined through comprehensive analysis,and the sensitivity analysis result of beam element is introduced into the optimization model of body structure based on the genetic algorithm,which narrows the searching space of design variables in the optimization process,and reduces the possibility that the optimization model falls into local optimum,thus improves the effectiveness of the optimization calculation results,and provides a new research idea for lightweight design of vehicle body structure.(4)A software system for the modular concept design of automotive body is developed,and the effectiveness of the system is verified by comparison.Based on the object-oriented MATLAB software development platform,a toolbox for the body structure analysis and optimization with graphical user interface is developed to realize the stiffness chain model,the novel joint model and the optimization method proposed in this paper.The software takes the static and dynamic performance of the body model as the calculation objective,in order to verity the effectiveness of calculation results,the structural performance between the mathematical simulation model and the initial body model,as well as the optimized body model and the initial body model,are compared and analyzed,the results show that the software system can effectively realize the structural performance analysis and optimization of body model,which confirms the feasibility of body modular conceptual design using stiffness chain method.