| In recent years,China’s new energy vehicles are booming.Lightweight design has an important impact on the endurance mileage of electric vehicles before the breakthrough in battery technology.Light alloy extruded profiles and sheets based on aluminum alloys are increasingly used in automobiles.Considering the layout of the vehicle and the profiles which are designed as the main body frame are different from traditional petrol vehicle,a separate method and process focusing on design and optimization of electric vehicles are proposed.In this paper,the initial design of the aluminum alloy frame body structure of the small electric vehicle and the lightweight optimization design based on the parametric model are carried out.The specific contents are as follows:The initial structure of the small electric vehicle frame body structure is established according to the structural size of the small electric vehicle,the material and sectional shape of the common profile of the vehicle body structure.The finite element model of the initial frame body structure is established and the bending stiffness,torsional stiffness and modal performance of the initial structure are calculated and compared with the benchmark vehicle and the target value.The parametric model of the body frame part was established by using the parametric modeling software SFE CONCEPT,and the simulation results is compared with the result of model established by the general finite element software and the actual frame body test results.The reliability of the parametric model is verified,which is the basis for the subsequent parameterization optimization.Together factors including dimensions,chassis and other related arrangements,the topology optimization design of autobody which is based on compromise planning method of minimum flexibility is performed,considering seven operating conditions.The initial body structure is improved with reference to the topology optimization results and the results of the previous simulation analysis.A parametric model of the improved body structure is established,the basic performance simulation analysis on the rapidly generated finite element is performed.Compared with the initial body structure,the performance is greatly improved and higher than the target value.In the improved parametric model of body structure,a total of 56 parameters including thickness,position and section three types of design variables are selected as the initial design variables to orthogonally design.Each test sample was calculated in the automatic analysis process of integrating modules such as SFE CONCEPT and solver in ISIGHT.After that,20 design variables were selected by comprehensively analyzing the corresponding contribution and main effect of each variable.Optimal Latin hypercube experimental design method was used to design 130 experiments,and different approximation models were established based on the sample data to express the relationship between the variables and the corresponding response.After the accuracy comparison,the response surface approximation model is used instead of the simulation program.The NSGA-II multiobjective optimization algorithm is used to optimize the multi-objective structure of the vehicle body with the target of the minimum mass and the maximum bending and torsion stiffness.The parametric model is adjusted according to the approximate model optimization results.And then,the finite element simulation is performed to ensure that the bending and torsion stiffness and the first-order bending and torsion mode frequency meet the design goal,and the positive impact performance of the vehicle body structure is almost unchanged.The weight of autobody structure is declined by 4.1%,compared with that of pre-optimization one and decreased by 11.7%,compared with that of original one.The credibility of the ALAlloy frame structure parameterization modeling could be confirmed,and the approximation method multi-objective optimization can be used in electric car body structure. |
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