Research On The Lightweight Design Of A Commercial Vehicle

With the development of automobile industry,lightweight technology has become the focus of major automobile manufacturers.In this paper,a commercial bus was taken as the research object.Based on the economy and structural safety of the whole vehicle,the optimization method of plate thickness was used for lightweight design to achieve the goal of cost reduction and efficiency increase.Firstly,the research status of lightweight technology at home and abroad was analyzed,then the basic theory of finite element method and multi-objective optimization method were expounded.After that,the finite element model of commercial vehicle was established,the accuracy of the model was verified by rollover test,and the static and dynamic performance of vehicle and frame were analyzed.Secondly,through the sensitivity analysis of frame's key parts,seventeen parts of the frame,including the longitudinal beam,were determined,and their thickness was taken as the design variable.Through the test design,the agent model was fitted,and the multi-objective optimization method was used to determine the frame lightweight scheme.This scheme could reduce 5.6kg weight,had good static and dynamic performance,and was safe and reliable according to fatigue analysis.By applying the frame lightweight scheme to the whole vehicle,the preliminary vehicle lightweight scheme was obtained.Then,considering the optimization cost and the feasibility of the scheme,it was determined that the stiffeners on the C and D pillars were the body parts that could be optimized,and their thickness was taken as the design variable.Through the test design,fitting agent model and optimization design,the vehicle lightweight scheme was obtained,which was 2.5kg less than the preliminary vehicle lightweight scheme.Finally,by comparing the simulation results before and after optimization,it could be concluded that the lightweight scheme could reduce 8.1kg weight in total,and increase the firstorder modal frequency while keeping the bending and torsional stiffness of the vehicle reduced by no more than 1.5%.Based on the commonly used lightweight evaluation methods,the lightweight indexes suitable for commercial vehicles were proposed,and the evaluation results showed that the vehicle lightweight scheme was better.Then,the vehicle lightweight scheme was analyzed by rollover simulation.The results showed that the upper structure strength of the scheme was qualified and the vehicle structure safety was good.