Multidisciplinary Design Optimization Of Pure Electric Vehicle Body Frame With Crash Performance

With the support of three “Five-year Science and Technology Innovation Plan” and “Industrial Science and Technology Innovation Project”,the development of pure electric vehicles in China has made a breakthrough progress.As a new mode of travel,pure electric vehicles make urban travel more energy efficient,safe,environmentally friendly and convenient.Miniaturized and lightweight pure electric vehicles will become an important direction for the development of automobiles in China.Therefore,it is more important to research on vehicle body lightweight of the small pure electric vehicle base on the Multidisciplinary Design Optimization(MDO)method.Aiming at the special frame structure of all-aluminum body,the new designed single-row and two-seat small electric vehicle is taken as the target model.Multiple response objectives in different disciplines such as static stiffness characteristics,modal performance and frontal crash safety performance are taken into consideration.Lightweight and MDO is done based on the vehicle body.The main research work and relevant conclusions are listed as follows:The basic theory of MDO is discussed.Five different experimental design methods are introduced,and then the establishment methods of three different approximate models are compared.Finally,four kinds of optimization algorithms are elaborated,which provides the theoretical basis for the subsequent MDO of vehicle body.Research on the method of modeling a pure electric vehicles finite element model.Based on the modelling requirements and methods,both of the simplified principle of components,details and quality requirements of mesh division,the simulation of connection mode of components,the definition of material properties and the setting of contact are introduced.Modular management of the vehicle model has been completed.The vehicle body and full vehicle frontal crash finite element model has been created.The test and simulation of the static bending,torsion stiffness,modality for vehicle body and frontal crash for the vehicle have been performed.Through the validation between simulation and test,the accurateness of finite element model has been validated.The key parameters of the multiple response objectives in different disciplines are extracted,and the response that needs to be optimized has been determined,which provides the data support for the subsequent lightweight MDO of vehicle body.In the process of MDO of vehicle body,reasonable selection of design variables can improve the optimization efficiency.Based on the Hamersley experimental design method,one hundred uniformly distributed sample points have been generated,the experimental design results have been analyzed by main effect analysis method,twenty eight parts' s thickness from vehicle body are selected as the coupling design variables,and the approximate model for stiffness is constructed by using the radial basis function method.The approximate model for the frontal crash is constructed by using the Kriging method.Based on the optimization design software Hyperstudy,with the approximate model of stiffness,modal and frontal crash of the vehicle body,the vehicle body lightweight is selected as objective,the bending and torsion stiffness,the first natural frequency and crashworthiness are selected as constraint indicators,and performs the multi-disciplinary optimization on vehicle body by global response surface optimization algorithm,and the basic performance of the vehicle body before and after the optimization is compared and analyzed.The results show that the optimized body has improved performance in terms of stiffness,mode,and crashworthiness,the mass of the vehicle body is reduced 5.13 kg,the lightweight coefficient is reduced by 19.2% and the lightweight effect is obvious.The effectiveness of the multidisciplinary design optimization method for lightening of vehicle body has been validated.