Research Andapplication Of Vehicle Rear Subframe Lightweight Method

With the emergence of the global energy crisis and global warming issues, lightweightdesign of the vehicle has become a hot research topic. Reducing vehicle weight, not only canimprove fuel efficiency, but also can reduce emissions of harmful substances. Rear subframeas an important carrier of vehicle chassis, connected with the body and suspension systems,improve not only the ride comfort and handling, but also the suspension assembly versatilityand convenience.Based on a plug-in hybrid car lightweight project, lightweight design methods for rearsubframe of a model were discussed in this paper. Combined with the vehicle dynamicstheory, the finite element technique and structure optimization methods, the paper conductedmulti-body dynamics, static and dynamic characteristic analysis and structural optimizationfor rear subframe under multiple loading conditions.Based on the vehicle road test, analysis offatigue durability of the rear subframe was carried out and the results verified the feasibility ofdesign method and achieved good lightweight effect.This paper firstly introduced the background of the lightweight research for automobilerear subframe, and then described its purpose and significance. Upon detailing the structurecomposition, classification, material selection and function of the rear subframe, this workproposed the research contents and routes. The dynamics analysis of the rear subframestructure of the plug-in hybrid electric vehicle as well as its static analysis under five typicalconditions was then conducted, thereby each hard point load data of the rear subframestructure was obtained, which provided load boundary condition for its optimization. Byanalyzing the characteristics of the rear subframe structure, its finite element model (FEmodel) was established and the strength, stiffness and free model analysis was then conducted.The rationality of the model was analyzed and verified. The results showed that the structuralperformance could satisfy the requirements of enterprises, that the performance margin islarge and that the structure has a large potential of lightweight.The size optimization of rearsubframe structure is aimed at obtaining the optimal thickness combination. Upon clearlydesigning variables, constraints as well as design objective, DOE was carried out for the rearsubframe structure and obtained its sample point database. Furthermore, the response surface approximate model and radial basis approximate model were established based on thesesample points. By comparing and analyzing the prediction precision of these two approximatemodels, we selected the response surface approximate model of high precise to conductstructural optimization. Then by applying NSGA-II multi-objective algorithm, optimalthickness composition was obtained, which make the rear subframe structure fully satisfydynamic performance requirements and reduce the weight of the rear subframe structure of5.6%.Performance of thickness optimization scheme for rear subframe structure was verified,including analyzing and revising the stiffness, free modal and fatigue resistance. Resultsshowed that the optimized rear subframe structure could fully satisfy both dynamics/staticsperformance requirements of enterprises and could adapt to the actual highway conditions. Asa generic technology, this method for structure optimization design can be used extensivelyfor the lightweight design of automobile rear subframe of the different type.