Research On The Lightweight Design Of A Heavy-duty Truck Frame

Improvement of the cars has become an important direction of the automotiveindustry innovation since the oil crisis of1973. Lightweight problem is one of thefocuses of attention of people; the main reasons for this are the energy problem andthe global environment problem. With the increasing pressure of the energy and theenvironment, all countries in the world pay more and more attention to thecoordinated development of resources and the environment. In order to get thesustainable development of trucks, its energy saving and environmental protectioncharacteristics must be improved. The truck frame lightweight research has importantsignificance to the enterprise themselves, the users and the whole society.In order to research and develop the high-performance products with theexcellent structural performance, light weight, and achieving the country’sindustry-leading level, Changsha Foton Motor Co., Ltd. is in cooperation with HunanUniversity to carry out a project for analyzing and optimizing of a certain truck frame.The research content of this thesis comes from the project, and the main task of thisthesis is to research the problem of lightweight of the truck frame and to achieve thepurpose of lightweight design of the truck frame on the basis of meeting the stiffness,strength and the vibration performance requirements.The main research works of this paper are list as follows:(1) The finite element model of a certain truck frame’s structure is established inHyperMesh by using the CAD model which is provided by Changsha Foton Motor Co.,Ltd. And then some key issues which are needed to pay attention to in establishing thefinite element model are analyzed and discussed.(2) The static response analysis of the frame structure is carried out on twotypical working conditions, namely the bending working condition and distortingworking condition. As a result, the stress and displacement distribution of the frameunder two typical working conditions are obtained, and the strength of the analysisresult is checked. It can be seen from the static response analysis results that the truckframe has good structural performance and it can well satisfy the requirements ofstatic strength, which provide the basis for the further optimization design and theimprovement of frame structure.(3) On the basis of the established finite element model of the frame structure, the modal analysis of the frame structure is carried out. The modal analysis resultsshow that the first-order torsional frequency of the truck frame structure is8.90Hzand the first-order transverse bending frequency is15.42Hz. The finite elementmodal analysis results indicate that the first-order torsional frequency and thefirst-order transverse bending frequency of the truck frame meet the designrequirements and the occurrence of resonance phenomenon can be effectivelyavoided.(4) By taking the plate thickness as the design variable, the response surfaceapproximation model of the maximum bending stress and maximum torsional stress ofthe frame are established. Meanwhile the error analysis of the response surfaceapproximation model is carried out by using the significance analysis method. Theerror analysis results indicate that the corresponding response surface model isreliable and can be applied to subsequent research and analysis. Finally, the geneticalgorithm is employed to optimize the approximation model, and the optimalthickness value of the frame panel is obtained according to the result of optimization.The weight of the optimized frame has decreased from712.6kg to652.2kg. Underthe premise of ensuring the stiffness and strength, the purpose of the lightweight isachieved.The research object of this thesis is a truck frame. At first, the finite elementanalysis of the truck frame is carried out. And then, taking the maximal stress and themaximal stress under two kinds typical working condition as the constraint condition,the lightweight design of the frame structure is accomplished by using the responsesurface approximation model and the optimization method. This thesis did a systemicstudy for the establishment of the finite element model of the frame structure, thestatic characteristic analysis, the modal analysis of the frame structure and thelightweight design of the frame. The research results of this thesis may of some valueto the practical research and development of the truck frame.