Structural Design And Optimization Of Steel-aluminum Hybrid Body For Small Electric Vehicle

Under the background of peak carbon dioxide emissions and carbon neutralization,lightweight is one of the important means of energy conservation and emission reduction.With the application of lightweight materials such as high strength steel and aluminum alloy,‘ appropriate materials are used in appropriate positions ’ has gradually become the guiding ideology of body lightweight.In recent studies on multi-material body material selection,material selection is mainly carried out for a single body structure component or materials are added to the multi-objective optimization process as design variables.There is a lack of body performance-material attribute matching criteria considering the overall structure.Secondly,multiple attribute decision making methods with single subjective or objective weight are often used in the process of Pareto solution set selection,so the accuracy of the final optimization scheme is insufficient.This paper takes the steelaluminum hybrid body structure of small electric vehicles as the research object.Through the combination of entropy weight-TOPSIS method and topology optimization results,the body performance-material attribute matching criterion is established.The reliability multi-objective optimization design is carried out for the implicit parametric model of steel-aluminum hybrid body.The optimal scheme is determined by grey correlation analysis method with combination weight,and its feasibility is verified by simulation.Then,the steel-aluminum hybrid body structure design and reliability optimization design method are established,which provides reference for the design and development of multimaterial body structure of electric vehicles,and has engineering application value.The specific content of this paper is as follows :The ranking scheme of materials based on mechanical properties is determined by entropy weight-TOPSIS method,which considers the mechanical properties of different steel and aluminum materials.Secondly,referring to the size of small electric vehicles,considering seven kinds of dynamic or static conditions,the topology optimization of the body is carried out based on the compromise programming method with the minimum overall flexibility as the goal.Then,according to the topology optimization results and material ranking scheme,the body performance-material attribute matching criterion is established,which can realize the vehicle structural material screening.Finally,the section of aluminum profile structure is designed.On this basis,the initial structure of steelaluminum hybrid body is established.The initial parametric model of steel-aluminum hybrid body is established by SFEconcept.The static performance of the finite element model is analyzed,which is quickly generated by parametric model.Compared with the existing finite element model performance analysis results,the accuracy of the parametric model can be obtained,which lays the foundation for the subsequent multi-objective optimization.Based on the parametric model of steel-aluminum hybrid body structure,50 initial design variables were selected,including plate thickness,beam section parameters and beam structure position.The automatic simulation analysis platform is built by Isight combined with parametric modeling software SFE-Concept and finite element analysis software Optistruct.The optimal Latin hypercube method is used for data sampling to obtain the Pareto diagram and the main effect diagram of the initial design variables.Considering the contribution of different variables and the equivalent main effect value,23 design variables were selected as the subsequent optimization variables,and 150 groups of experimental designs were carried out by the optimal Latin hypercube method.The response surface model,radial basis function neural network and Kriging approximation model are established according to the sample points of the collected experimental data.And the response surface model is selected as the optimization model due to its good accuracy.The multi-objective optimization of the reliability of the steel-aluminum hybrid body structure uses NSGA-II multi-objective genetic algorithm.In this optimization,the minimum vehicle weight,the maximum bending and torsional stiffness are taken as the objectives,and the first-order bending and torsional modes,stiffness and the 6 Sigma mass level of the optimization objective are taken as the constraints.On the basis of the obtained Pareto solution set,the grey correlation analysis method based on combination weight is used to determine the optimal solution,and the feasibility of the optimal scheme is verified by finite element analysis.Then,based on the above process,the deterministic multiobjective optimization design of steel-aluminum hybrid and aluminum body structure is carried out,and the effectiveness of the optimization scheme is verified by finite element analysis.The results show that the multi-objective optimization design of steel-aluminum hybrid body based on reliability achieves weight reduction of 3.55 %,bending and torsional stiffness increases by 38.31 % and 4.88 %.Compared with deterministic optimization scheme,the reliability requirements of each optimization objective are further satisfied.At the same time,compared with the deterministic optimization scheme of aluminum body,the lightweight effect of steel-aluminum structure is remarkable.Therefore,this paper aims at the design and optimization of steel-aluminum hybrid body structure of small electric vehicles,including material selection based on body performance-material attribute matching criterion and reliability optimization design of vehicle structure.The results are reasonable and effective.Structural design and optimization of steel-aluminum hybrid body for small electric vehicles is an effective method.