| With the increasingly serious problems of environmental pollution and energy crisis,China is vigorously developing the new energy vehicle industry,and there are problems such as low cruising range and collision safety during the promotion of pure electric vehicles.At present,the energy density of power batteries is slowly increasing,so it is urgent to improve the endurance performance through the weight reduction design the structure.As the support and protection structure of the battery,the battery pack has a high requirement of crashworthiness.Its lightweight design must ensure the collision safety.Therefore,it is urgent to develop a lightweight design method with collision safety.In this paper,the structural characteristics and modeling methods of the power battery pack are studied,and a lightweight design method for improving the crashworthiness of the battery pack based on morphology optimization and multidisciplinary optimization is established.The main research contents and results are as follows:(1)Modeling method for power battery pack structures and their finite element analysis.First of all,from the three aspects of material,manufacturing process and structure,this chapter mainly introduce the common lightweight methods and structural characteristics of battery packs.Secondly,according to the design requirements of battery pack collision safety,a refined finite element modeling method for battery packs is proposed.Taking a typical electric vehicle power battery pack as an example,the geometric analysis of the battery pack is carried out.Then combining material and structural features,through geometric simplification and cleaning,Mesh division,model assembly,and finally establish a refined finite element model containing the battery pack and the internal force transmission frame to verify the effectiveness of the modeling method.(2)Structural safety analysis of battery packs and identification of structural protection functions.Static simulation was carried out for four typical driving conditions of the vehicle: forward braking,reverse braking,sharp turning and vertical turbulence.Stress distribution and deformation of the battery pack structure were analyzed and its static characteristics were evaluated.The first ten mode modes and natural frequencies were calculated by modal analysis of the battery package,and the dynamic characteristics were evaluated.According to the requirements of relevant laws and regulations,the collision and squeeze condition of the battery pack was simulated,the collision safety was evaluated,and the safety design requirements of each condition were determined based on the simulation results.A hierarchical optimization strategy based on structural protection function identification is proposed to provide reference for subsequent structural optimization and weight reduction design.(3)Design optimization of lightweight material components based on optimization of morphology and structural characteristics.The Non-main protective structures was optimized.Optistruct solvers is used to optimize the design of the rib structure,composite material lay size and lay order,which improves the dynamic stiffness and reduces the quality of the cover from 19.5kg to 9.33 kg.Further replace the material of the battery pack structure with aluminum alloy,set a custom objective function based on the eclectic planning method,take static multi-case topology optimization design for the floor stiffener,and perform multi-case optimization on the size of other non-main protective structures.While satisfying the safety requirements of static and dynamic working conditions,the weight of the structure is reduced.(4)Design optimization of the main protective structure of the battery pack based on multidisciplinary optimization.The main protective structure is divided into crash-resistant functional zones.The thickness of the main protective parts such as the partition box,side wall stiffener and bead is the design variable,the minimum structural quality is the objective,and the safety standards of each working condition are the constraints.A multidisciplinary optimization model is established based on the Hyperstudy platform.Samples are collected through the hammersley experiment design method.The variables and responses are extracted through simulation analysis and the approximate model is built.The global response surface algorithm is used to optimize the size of the components of the battery pack to meet the crashworthiness requirements and reduce the quality at the same time.The optimized results show that the first-order modal frequency of the battery pack is increased from 12.67 Hz to 30.22 Hz and the maximum displacement of the bumpy working condition is reduced from 6.75 mm to 1.97 mm,while meeting the safety requirements of collision and squeeze working condition.The total mass of the structure was reduced from 447.7kg to 383.3kg,the weight loss accounted for 14.38%,and the weight loss ratio of the optimized components reached 60.58%,which indicating that the weight reduction effect is significant. |
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