Lightweight Design Of Skeleton Structure Of Full-load Pure Electric Bus

With the world’s energy depletion and global environmental changes,energy conservation and emission reduction has become the primary goal of various industries.For the passenger car industry,the lightweight design of the pure electric bus body frame is of great significance to the energy saving and emission reduction strategy.There are three main methods for passenger car lightweight:optimized design methods,new material technologies,advanced manufacturing processes and their connection technologies.This paper will combine the above methods to lightweight design of a pure electric bus body frame.The CAD model of.pure electric bus body skeleton is established by UG three-dimensional drawing software,and the CAD model is imported into Hypermesh software to establish the finite element model.The modal analysis,stiffness analysis and strength analysis of the pure electric bus body frame are carried out by the finite element method.Through analysis,it can be obtained that the body frame of the pure electric bus has a low stiffness value and a local stress is too large.Therefore,this paper firstly maximizes the rigidity of the vehicle skeleton through topology optimization design,and has a certain margin for the stiffness performance of the standard industry standard.Through the size optimization of the relative sensitivity analysis combined with the steel-aluminum hybrid material,the lightweight design of the pure electric bus skeleton is realized.Due to the simple structure of the car body,the mature square steel construction and the small topological space,this paper only optimizes the topology of the pure electric bus.Using the variable density method of SIMP difference with the volume fraction as the constraint and the minimum flexibility as the objective function,the topology optimization of the multi-mode linear weighting of the pure electric bus undercarriage is carried out.According to the first round of topology optimization results,the force analysis is carried out,and the second round of topology optimization is expanded after the topological space is partially expanded.Finally,according to the topological results,the square steel of the relevant skeleton is constructed,and the stiffness value and skeleton quality before and after the topology are compared.After two rounds of topology optimization,the bending stiffness and torsional stiffness values reached the industry standard,with an increase of 50.1%and 35.1%,respectively,and the chassis quality was reduced by 48kg.In order to further reduce the weight of the vehicle skeleton,this paper optimizes the size based on the steel-aluminum hybrid body with relative sensitivity.Firstly,the mechanical properties of steel and aluminum thin-walled beams are compared and the finite element simulation is used to verify the selection of "X"-shaped aluminum alloy thin-walled beams instead of steel thin-walled beams.The relative sensitivity of the aluminum alloy replacement steel is determined by the relative sensitivity method.Finally,the size optimization is carried out.The specific thickness of the steel of the final passenger car skeleton is obtained.Compared with the original model and size optimization,the mechanical properties and quality of the passenger car skeleton can be obtained:the quality of the bus skeleton is reduced by 241kg,and the weight loss rate reaches 10.9%.The stiffness performance,strength performance and modal performance of the passenger car skeleton structure are effectively improved.That is to say,this optimization achieves lightweight design while effectively improving the mechanical properties such as rigid strength and modality of the passenger car skeleton.