Structural Lightweight Research On Large Bus Frame

The aim of this paper is to highlight the importance of lightweight vehicle structure, provide an overview of domestic and overseas research, analyze the technological development trend and discuss the flaws of domestic research in this field, and put forward the design idea of using Finite Element Method (FEM) to analyze and optimize the frame of large bus.Subsequently, shape optimization, topology optimization and size optimization have been introduced, and these optimization methods applied in structural design of a foreign bus body frame have been discussed. In order to meet the client's demand to keep the structural shape and topological layout of the bus frame unvaried and only modify the thickness of the components, the size optimization has been chosen as initial project to lighten the bus frame.Then, the theory and conception of elastic mechanics and Finite Element Method (FEM) have been discussed. The all-shell-element model of the large bus frame has been built according to the drawing provided by the client, stress and displacement of the whole bus frame under curve and torsion load cases have been computed, and finally strength and stiffness of the bus frame has been obtained. Several improvements on the frame have been made to eliminate the high stress concentration on small joints.Based on research above, in order to effectively lighten the weight of bus frame, size optimization research model has been built including setting the shell thickness of the base, side wall as design variables, the element maximum stress of all load cases as state variables and the whole large bus frame's volume as objective function. From this model the structure weight has been reduced by 14.5% and the design demand of strength and the stiffness have been met.The research results of this paper have not only provided effective computational model and numerical method for the structural analysis and design of the large bus frame, and solved problems of the enterprise but also has improved the design level and efficiency, shortened the design periods, reduced the cost, and provided valuable reference for domestic manufacturers.