Topology Optimization And Robust Design Of Underbody Structure For Pure Electric Car Based On Performance Driven

With the increase of car sales and ownership,a series of environmental problems have been brought to the society.Therefore,in order to achieve the harmonious and healthy development of cars and society,we must vigorously develop pure electric cars.However,there is not much research on the design of pure electric vehicles,especially the non-bearing underbody at present.Most of them are modified on the basis of the traditional fuel body.Therefore,it is necessary to carry out research on design and optimization method of the non-bearing underbody of pure electric vehicle,and it has very important practical application value.In this paper,the nonlinear crashworthiness analysis method,topology optimization method of multi-working conditions,response surface model improvement method and robustness optimization method of the underbody of the non-bearing type vehicle are studied systematically at first,and finally the structure obtained is applied to the whole vehicle for crashworthiness analysis and verification.The main contents are as follows:(1)Research on topology optimization under mult-working conditions of the non-bearing underbody of pure electric vehicle.In order to solve the problem of structural nonlinearity under the condition of automobile collision,a hybrid Method(IRF-IRM)based on the idea of combined with the Method of inertial release and Equivalent Static load is proposed in this paper.The method can introduce the average collision force including the maximum peak value in the collision condition as the boundary condition into the analysis of the inertial release method,and then apply the hybrid method to the topological optimization of crashworthiness design base on IRM and ESL Methord.Finally,the method is applied to the forward concept development of the non-bearing underbody of Zhongtaiyun 100.Multi-case topology optimization is carried out by dividing the design space into different schemes.The optimization takes into account a variety of collision conditions(forward collision,side collision and rear collision)and a variety of static conditions(overall bending stiffness,overall torsion stiffness,overall braking stiffness,overall acceleration stiffness and overall turning stiffness).The results show that the method proposed in this paper can realize the optimization analysis of the nonlinear crashworthiness problem,and the material distribution obtained by various zoning schemes has a good consistency.The optimization method has a good meaning for the concept development and design of the structure.(2)Research on energy-absorbing structure design of pure electric vehicle based on crashworthiness.In order to obtain a clearer force transmission path of the rear cabin structure,the rear cabin design space of the underbody was extracted separate,and topology optimization is performed by TOCDM-IRMAESL method and HCA method respectively.Comparing the optimization results of the two methods,it is found that the result obtained by TOCDM-IRMAESL method is more consistent with the actual situation.This is because the equivalent loading force is uniformly applied on the rear end of the design space,so a thin plate similar to the rear bumper is formed.However,HCA method is direct collision with rigid wall,so the optimization results only show four main force transmission paths.Combining the results obtained by the two methods for engineering interpretation,two different rear cabin wireframes can be obtained.In order to further improve the crashworthiness of the vehicle,based on the TOCDM-IRMAESL method,carries out the lightweight design of the front energy absorption structure assembly based on crashworthiness,and then interprets it into a new front energy absorption structure assembly.The new structure obtained by this method can satisfy both the axial and longitudinal stiffness requirements and the maximum axial energy absorption.(3)Research on robustness optimization of front-cabin energy absorption structure of pure electric vehicle based on improved response surface method.In order to efficiently solve the multi-objective robust optimization design problem in engineering,an improved response surface method with residuals as input based on radial basis function and polynomial response surface was developed.It can improve the accuracy of the agent model under the condition of limited sample points.The NSGA-II algorithm is used to optimize the multi-objective robust optimization on the basis.Applying this method to front energy absorption structure assembly,the numerical results show that the accuracy of the proxy model obtained by the improved model accuracy is higher than conventional polynomial response surface.In addition,the crashworthiness of front energy absorption structure assembly obtained by robust design is reduced to some degree,the method not only makes the optimal solution of better robustness,the robustness of the design variables and constraints are also improved.(4)Multi-objective innovative design of non-bearing battery box assembly for pure electric vehicles.In order to verify the versatility of a series of optimization methods proposed in this paper on the development and design process of pure electric vehicle structure,the battery box assembly is taken as an example.Combining with the topology optimization theory and practical engineering,the concept development and design of the battery box assembly is firstly carried out through the TOCDM-IRMAESL method.This method takes into account both static,modal and crashworthiness characteristics to optimize topology and shape.The results show that the method can be used for multi-objective parallel optimization,making the optimization results more consistent with the performance requirements of actual working conditions.On this basis,we enter the detailed design stage of size optimization,five design variables were extracted through relative sensitivity analysis,and IRSM-RBF method was used to obtain high-precision response model through two residual interpolation,and a multi-objective robust optimization design was developed.The design of the battery box assembly proves that the relevant research methods proposed in this paper can provide an efficient,reliable and fast optimization design process for engineering,and has guiding significance for the concept development of the rest of the vehicle structural parts.Finally,the main energy absorption structure of the front and rear compartment and the battery box assembly are tested for the crashworthiness of the vehicle through a simple rigid connection.It shows that the optimized pure electric car has good front and side impact resistance.