Research On Lightweight Design Of Steel-aluminum Hybrid Heavy Truck Frame

China’s car ownership has increased year by year.In the field of commercial vehicles,medium and heavy trucks and light trucks are the main force for the continuous growth of the number of commercial vehicles.The increase of the number of vehicles inevitably brings the problems of energy consumption and emission,especially the fuel consumption of commercial vehicles accounts for about 55% of the whole automobile industry.The research on the lightweight design of commercial vehicles is of great significance for energy conservation,emission reduction and improving economic benefits.The design of the domestic mainstream heavy truck frame is still based on the traditional high-strength steel,but due to the restriction of the inherent density of steel,it is no longer possible to significantly reduce the weight of the frame,which limits the improvement of the lightweight design level of the heavy truck frame.Based on the investigation of the current situation of commercial vehicle lightweight at home and abroad,combined with the finite element theory and the characteristics of aluminum alloy materials,this paper puts forward the lightweight scheme of steel aluminum hybrid heavy truck frame with performance driven structure optimization.Based on the research of the steel frame of a domestic heavy truck tractor,under the constraints of a certain design boundary,the section and thickness of the parts are optimized,and the structural design of the first steel aluminum hybrid frame with aluminum alloy instead of steel is completed.Compared with the original steel frame,the weight of the first steel aluminum hybrid frame is reduced by 256.3kg,and the weight reduction ratio is 37.3%.By means of simulation analysis and optimization,the finite element model of the first steel aluminum hybrid frame is built,and the stiffness,mode,strength and other properties are analyzed.Based on the performance of steel frame and the principle that the performance of lightweight frame is not lower than that of steel frame,it is found that many properties of the first version of steel frame can not reach the level of the original steel frame,especially the reduction of bending stiffness by 24.6%,which needs to be paid special attention,and the structure of the first version of lightweight frame needs to be optimized and improved.On the basis of the structure of the first steel aluminum hybrid frame,the structural optimization is driven by performance,combined with the topological optimization analysis results based on the bending stiffness condition,the multi wheel optimization,analysis and verification of the structure strengthening of the frame longitudinal beam,cross beam,connecting plate and other parts are carried out,and the design scheme of the final steel aluminum hybrid frame with satisfactory performance is obtained.The weight of the final lightweight frame is468.3kg,which is 218.5kg lower than the 686.8kg of the original steel frame,with a weight reduction ratio of 31.5%.Based on the structural data of the final steel aluminum hybrid frame,the sample parts of the frame aluminum alloy are manufactured,and the loading and reliability road test verification of the whole heavy truck tractor are completed.According to the test results,the frame aluminum alloy longitudinal beam body cracked and the corrugated plate cracked,two parts failed,and other aluminum alloy parts met the test requirements.Through the troubleshooting and analysis of the fault problems,it is known that the fault is mainly caused by the failure of the strength of the aluminum alloy weld position to meet the requirements and the certain difference between the actual vehicle state and the design scheme.After the structural optimization and simulation check of the fault parts,according to the analysis results,the optimized structure can meet the performance requirements,which will be verified by subsequent tests.In this paper,the performance of the original steel frame is taken as the evaluation standard,and the performance margin of the original steel frame is not considered.The performance goal of the lightweight frame is relatively conservative,resulting in the weight of the lightweight frame is not the optimal state.In addition,the analysis,research and test verification of the front impact safety performance of the cab of the whole vehicle are not carried out for the frame,and the performance consideration is not comprehensive enough.Through the research of this paper,it can be seen that the engineering design scheme of steel aluminum hybrid heavy truck frame is feasible,and the application of aluminum alloy materials in the lightweight field of commercial vehicles is promising.With the continuous engineering application of aluminum alloy and other lightweight materials,the lightweight design level of commercial vehicles will be greatly improved.