Finite Element Analysis And Lightweight Design Of A Pure Electric Bus Body Frame

As one of the key development directions of China's automobile industry in the future,pure electric vehicles have the characteristics of environmental friendliness,energy saving and emission reduction,high efficiency and high quality.Therefore,most of today's urban buses are basically electric buses.Because the total mass of the battery of a pure electric bus is large,in order to meet the requirements of stiffness and strength,the pure electric body frame is heavier than the traditional bus body frame.The body frame accounts for a high percentage of the mass of the entire vehicle,and its percentage is about 35%-40%.Therefore,the weight reduction of the pure electric bus body frame is of great significance to reduce the quality of the entire vehicle.In this paper,a finite element analysis is performed on the body frame of a pure electric bus on the market,and the topological optimization method,empirical optimization method,and material replacement method are used to lightweight its design.First,the field survey and measurement of the pure electric bus were carried out,and the digital model was drawn.Then,a finite element model was established,and a finite element analysis was performed.This phase of work is divided into two parts: the first part,the static analysis of the structure of the car body frame under four typical conditions of bending,extreme torsion,sharp cornering and emergency braking.Calculate the stress and deformation values of the body frame under various working conditions,and propose a method for dealing with the lateral stabilizer bar in the static analysis of the body frame.In the second part,a modal analysis is performed on the body frame to obtain the first 10 orders of free vibration frequencies,and the results meet the relevant design specifications.Then,based on the results of static analysis and modal analysis,the topology optimization analysis is performed on the body skeleton using the topology optimization method.According to the results of topology optimization,the relevant design specifications of the body frame and the manufacturing process,the structure optimization of the body frame is performed.After topology optimization,an empirical optimization method is used.This part first uses experience to reduce weight and rebuild,and then changes the arrangement of the battery to increase the front axle load percentage,thereby improving the maneuverability of the vehicle.After the first two steps,static analysis is performed on the optimized body skeleton under four typical working conditions,and modal analysis is performed on it.After obtaining the results,the corresponding data of the optimized body skeleton is compared with the original body skeleton.The results show that the optimized body skeleton has a mass reduction of 6.61% compared with the original body skeleton;In terms of strength,the maximum stress value of the body skeleton after the optimization of the structure is lower than the maximum stress value of the original body skeleton,and the maximum stress drop percentage is above 18%,which indicates that the optimized body skeleton has better strength characteristics;In terms of frequency,the optimized body skeleton avoids the corresponding excitation interval;In terms of anti-deformation ability,the anti-deformation ability of the body skeleton after structural optimization is slightly lower than that of the original body skeleton,but the maximum amount of deformation is smaller than the deformation standard adopted in this work condition.This shows that the optimized body frame still meets the performance requirements in terms of resistance to deformation.Finally,after several analyses on the basis of optimizing the body skeleton,the final choice was made to replace its front wall and roof material.In terms of mass of the final body frame,its mass is reduced by 358.8kg compared to the original body frame,and the weight reduction percentage is 14.82%;In terms of strength,the maximum stress value is lower than the maximum stress value of the original body frame,and the maximum stress drop percentage is more than 11%,which indicates that the body frame of the scheme has better strength characteristics;In terms of frequency,the body skeleton of the final solution avoids the corresponding excitation interval;In terms of anti-deformation ability,the anti-deformation ability of the car body skeleton of this scheme is slightly lower than the original car body skeleton,but the maximum deformation is less than the deformation standard adopted in this paper.This shows that the body frame of the final solution still meets the performance requirements in terms of resistance to deformation.After comprehensive analysis,the body frame of this scheme was selected as the body frame of the final lightweight design.In this paper,during the finite element analysis of the body frame of a pure electric bus,according to the actual connection mode and position of the suspension and the body frame,constraint simulations that are more in line with the actual working conditions are made,and the processing method of the lateral stabilizer bar in the analysis of the body skeleton is proposed.In the subsequent lightweight design process,the empirical method,topology optimization method,and battery replacement method and material replacement method are used.In the subsequent lightweight design process,the topological optimization method,the empirical optimization method,and the method of replacing materials were used to establish a body frame that was relatively in line with relevant design specifications and actual manufacturing processes.The above has practical reference and guiding significance for the design and completion of subsequent optimization and improvement of passenger cars.