Load Transmission Path Based Aluminum Body Optimized Design Of Electric Vehicle Under Frontal Crashing

Automotive safety,energy conservation and environmental protection have become the three major themes of automotive industry.With the increasing national support for the electric automobile industry in recent years,the production and ownership of the electric automobile increased rapidly.Meanwhile,there are rapid growth trend in the number of car accidents in 21st century.Therefore,the research of car body crashworthiness for the electric automobile has become the research focus.To protect the occupant and battery effectively in electric vehicle frontal crashes and the research on how to design the optimum load transmission structure for vehicle collision with high efficiency and precision have become the urgent problems that need to be solved.Based on those analyses,the design and optimization methods based on load transmission path for aluminum body of electric car are proposed in this paper.The main contents and innovations are as follows:Firstly,a mechanical transmission path planning method for electric vehicle body is proposed.In this approach,the equivalent static load method and expert systems are applied.Total vehicle styling and layout parameters are chosen as input conditions.The electric vehicle body topology optimization model is established with considering the complex linear and nonlinear conditions.Meanwhile,the generating method of the mechanical transmission path of electric vehicle body and a battery pack structure are investigated systemically to determine the optimum material distribution of electric vehicle body and obtain the rational,efficient and optimal mechanical transmission path.At last,the optimum electric vehicle body frame structure is obtained based on the engineering interpretation of the topology optimization results.Secondly,a shape optimization method,which based on the HCA method,for optimizing key parts cross section in frontal crash is proposed.After studying the load transmission path for aluminum body of electric car,the nonlinear dynamic topology optimization mathematical model based on the frontal crash is first constructed for the key energy-absorbing components such as front anti-collision beam and front longitudinal beam.To deal with the condition of highly-nonlinear and dynamic loads,the SIMP model which based on the variable density method and HCA method is applied to perform the topology optimization.The local control rule is also established to modify the unit density in the optimization process.The topology optimization results of the cross section for the front anti-collision beam and front longitudinal beam are obtained through multiple iterations.It can be concluded from the topology optimization results of the cross section for the front anti-collision beam and front longitudinal beam that the crashworthiness of the electric vehicle is improved significantly.Thirdly,a cross section parametric design method which based on the mechanical transmission path of electric vehicles in frontal crash is proposed.Based on the topology optimization results for the electric vehicle body,the full parametric model of the electric vehicle body,which based on the implicit parametric technology,is established and the parametric design method for cross-section is also proposed.In the parametric design optimization process for cross-section,the responses and design variables are established based on the results of cross-section force in load transmission path.The Kriging Meta model is constructed through Latin hypercube experimental design method.At last,the parametric optimization of the cross section,which based on the mechanical transmission path of electric vehicles in frontal crash,is performed by applying the multi-objective genetic algorithm.The peak acceleration value of the vehicle is improved significantly in the optimization and the mass of the key parts are also reduced.Fourthly,a joint parametric design method,which based on Kriging surrogate model,of multi-body restraint system and FEM body is proposed.The vehicle acceleration curve libraries are built by selecting the thickness of key parts as design variables and choosing storage battery protection as objectives and constraints.The joint parametric design model is then established by specifying acceleration curves in curve library as discrete design variables and assigning parameters of occupant restraint system as continuous design variables.Better occupant responses and storage battery protection are obtained by conducting the optimum analysis of occupant response.By comparing the results with those of the traditional design method,it can be concluded that better protection of occupant and battery can be obtained by the joint parametric design method.The research in this work shows that the optimum load transmission path for the electric vehicle body frame can be achieved effectively and the cross section shape of the key parts in load transmission path can be also optimized by combing the gradual spatial topology optimization method and HCA nonlinear dynamic topology optimization method.Based on the topology optimization results of the electric vehicle body,the full parametric model of the electric vehicle body,which based on the implicit parametric technology,is established and the optimization design of the cross section and plate thickness in load transmission path can be performed effevrively.By applying the joint parametric design method of multi-body restraint system and FEM body for electric vehicle,the occupant and battery can be 1 protected much better.The conclusions in this work are meaningful for the crashworthiness design of the electric vehicle body in future.