Research On The Lightweight Of An Electric Bus

The main trend of modern automobile development is energy conservation and emission reduction.The lightweight design of automobiles is one of the most effective ways to achieve energy-saving and emission reduction of automobiles.The lightweight design of the vehicle can not only greatly improve the fuel economy of the vehicle,but also has a great influence on the power performance of the vehicle.For light buses,the frame is the most important load-bearing structure.The weight of the bus frame can account for 40%-60% of the entire vehicle weight.Therefore,the lightweight design of the passenger car frame is very important for the overall weight reduction of the vehicle.With the growing contradiction between the environment,energy,automotive industry and sustainable development,electric buses have come to the forefront.To increase the driving range of an electric bus,it is necessary to carry out lighter modifications.In this thesis,a lightweight electric vehicle with a length of 6.4m is designed.Based on the finite element method,the strength and stiffness of the car frame structure are analyzed.The finite element model of the carbody skeleton was established using the shell element of HyperMesh software,and the common full-load bending and full-load torsion working conditions during vehicle driving were analyzed.At the same time,the free mode was analyzed to obtain the car frame skeleton strength,stiffness and modulus.State and other structural performance parameters lay the foundation for the lightweight design of the rear body frame.The torsion and bending flexibility of the frame and the maximum of the first-order free modal frequency are taken as the objective function.The density of the area is optimized as the design variable.The volume fraction of the constrained design area does not exceed the given value,and the chassis and the roof frame are topologically After the optimization,the body structure after the topology is obtained,and then the relative sensitivity method is used to find the design variables that have a great influence on the vehicle weight but have little effect on the performance.Before the multi-objective optimization of the frame,the paper first uses the Hamlet's experimental design(DOE)method to sample the variables,and the sample points are calculated by finite element method.Based on the calculated data,a response surface model for the mass,stiffness and modal performance of the car body skeleton was established.Then use Hyperstudy's built-in multi-objective genetic algorithm(MOGA)to perform multi-objective optimization,aiming at minimizing the mass of the car body skeleton and the maximum of the first-order free modal frequency,and using bending conditions and torsional conditions as constraint conditions,using MOGA Target genetic algorithm for optimal design.Compare the performance of bending and torsion of the frame before and after optimization.The results show that the re-designed frame achieves a weight reduction of 71 kilograms and a weight loss rate of 8.5% under the premise of satisfying various performances.