Research On Asymmetric Body Understructure Of Integral Bus

Lightweight technology research of bus structure is one of the main methods and keyissues to save material, save energy and protect the environment. Since integral bus hasmany advantages such as lighter weight, better performance and better security than separateframe construction, integral bus has been developed rapidly in the passenger bus market. Thecharacteristic of most integral bus is integral bearing. The bending stiffness of body structureis largely influenced by body understructure and side surround structures. Usually, passengerdoors are designed at the right side of bus body which makes the bending stiffnessperformance of the right side weaker than the other side. However the body understructuredeveloped from the chassis of separate frame construction is still designed symmetrically. Asa result, the bending stiffness difference between left part and right part of the whole body isbig. As the traditional design can not evaluate the difference of performance between the leftside and the right one well, people focus to ensure that the side with passenger doors meetsload bearing requirements firstly. In traditional way, carrying capacity of some beams cannotbe fully used. Thus material is wasted. Dr. Gao Jianfeng proposed a structural design methodof asymmetric matching based on property complementary and a matching criterion ofstiffness performance. The purpose is to reduce the weight of the bus body and improve theperformance of the structure. But it has not been applied in reality.In this paper, based on the idea of complementation of the property, the applicationresearch of asymmetric matching design method is carried out on the side surroundstructures and understructure of an integral bus developed by an enterprise. The structureshould be designed reasonably to realize performance matching of the body structure. Thepaper focuses on the implementation of asymmetric body understructure. First of all, thebasic property of the original model should be analized to get the bending stiffness ratio ofthe two sides of whole body, the one of left side surround structure and right side surroundstructure, and the one of the two sides of body understructure. Combined matching criterionof stiffness performance, different methods are used to research the complementation of the property between the side surround structures and understructure. Local topologyoptimization method is adopted for asymmetric matching technology research on the bodyunderstructure, and the feasibility of this method is studied in the paper.This paper is divided into the following parts: Firstly, the basic performance of originalbody structure is analyzed, such as strength and stiffness of the structure. Mirror models ofunilateral structures are established to evaluate bending stiffness of unilateral body structures.Then, based on the study of stiffness evaluation method, stiffness matching technologyresearch on the side surround structures is carried to reduce the bending stiffness differencebetween them. Next, the main work of this paper is to optimize the body understructure bylocal topology optimization method. Not only to strengthen the weak area, but also optimizethe area strong enough to meet the performance requirements. Structures are designed tomake material distribute according to force situation. An asymmetric understructure isexpected to complement the performance difference between the side surround structures.The feasibility of optimizing body understructure on the basis of mirror models is studied inthe paper. The iterative method is adopted in the progress of optimizing body understructure.Thus, the accuracy of the optimization results is improved. The optimization progress hasnot been stopped until the results are convergence. Every local structure has been optimizedfour times till the result gets convergence. The interpretation rules of beam’s position andsize are also discussed. Last, the optimized model is analyzed to make a comparison with theoriginal model. At the end of this paper, a few research prospects are put forward.