| At present,the two major problems that restrict the development of the automobile industry are environmental pollution and energy crisis.To solve the above problems,new energy vehicles have emerged.The biggest bottleneck restricting the development of new energy vehicles is their cruising range.The lightweight of pure electric vehicles is an important measure to improve the endurance.The frame is an important assembly of the whole vehicle.The lightweight frame can effectively reduce the quality of the whole vehicle and improve the dynamic performance of the pure electric vehicle.This thesis studies a certain type of pure electric vehicle frame.Through the finite element software Hyperworks,the finite element simulation analysis of the frame is carried out,and the shortcomings in the design are found.To ensure the safety of the car,the Optistruct optimization module is used to study the local topological optimization of the vehicle frame.Based on the preliminary optimization,the orthogonal experimental design,the second-order response surface model and the nonlinear programming are applied to achieve secondary lightening of the frame.(1)Firstly,the grid model of the frame is created,and the frontal collision,modality,bending stiffness and torsional stiffness are analyzed.The safety performance of the frame is guaranteed to meet the relevant national standards before optimization.In the preliminary lightweight of the frame,the trabecular beam is selected to be optimized in the area,the frame is divided into three optimized areas,and the local topological optimization is made with the Optistruct optimization module.According to the force transmission path,the distribution of the trabeculae is made more reasonable without changing the cross-sectional shape of the beam,and the effective utilization of the trabecular material is improved,and the quality of the optimized area is reduced.In the optimization,the intrusion amount of the dash panel,the deformation of the girder,the first-order mode,the bending stiffness and the torsional stiffness are taken as constraints.(2)Secondly,after the initial optimization,the performance parameters of the frame are verified,and the frame is subjected to secondary weight reduction under the condition that the performance indexes of the frame can meet the relevant specifications.In this optimization,the material thickness of the front plate,the girders,the front beam,the rear beam and the rear plate in the frame are taken as a design variable.In addition to the above constraints,a B-pillar acceleration is added,and the frame quality is used as an objective function.The orthogonal test method is used to sample the constraint responses,and the obtained sample data is used to simulate the frame,and the corresponding constraint response values of each group are obtained.The second-order response surface model is used to fit the functions of each constraint response.The mathematical expression approximation agent model is constructed by analytic formula,and the multivariate function nonlinear programming model is solved and optimized by Lingo software.The optimization results show that the preliminary local topological optimization can reduce the total mass of the frame optimization area by 3.32%,and the weight reduction of the second step reduces the total mass of the frame by 14.63%.The lightweight is relatively successful.The optimized frame structure not only meet industry standards,but also reduced a lot of quality.Based on the frame simulation analysis,the Optistruct optimization module is used to complete the local topology optimization of the frame,and the mathematical methods such as orthogonal test,second-order response surface model and nonlinear programming are used to effectively realize the lightweight design of the frame.The second lightweight design enables the effective utilization of materials,while shortening the design cycle of the frame and reducing the design cost,which is of great significance for future lightweight research. |
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