2016 6 th International Conference on Information Technology for Manufacturing Systems (ITMS 2016) ISBN: 978-1-60595-353-3 Light Weight Research of Monocoque City Bus Body Frame Qiang Zhu, Xiaomei Li School of mechanical engineering, Zhengzhou University, Zhengzhou 450001, China ABSTRACT: The lightweight bus body frame can relieve coach mass for energy conservation and emissions reduction. With a monocoque city bus body frame as the research object, the finite element static analysis for the bus body frame is carried in ANSYS, considering four kinds of typical working conditions. By analyzing the calculation results, a lightweight body frame structure scheme is put forward. Through selecting AL6061 aluminum alloy and determining a steel aluminum connection mode, a steel-aluminum hybrid bus body frame structure is designed. Based on the steel-aluminum body frame finite element static analysis, the lightweight design for the monocoque bus body frame is achieved with a total mass reduction 10%, and the bus body safety requirements of strength and stiffness are also well met. It shows that the steel-aluminum body frame structure is reasonable and lightweight effect is obvious. KEYWORDS: Monocoque body; Finite element analysis; Steel-aluminum hybrid structure; Lightweight 1. INTRODUCTION Monocoque bus body is a closed loop structure with chassisless construction, the whole body bearing load and forming an integral structure, it will reach a stable equilibrium state when undertaking load [1]. The bus body frame with monocoque structure will be more safety, comfort and reliability. The lightweight bus body is aimed at reduce the mass at the same time the bus body satisfying the requirement of the security strength, thus achieving the goal of energy conservation and emissions reduction. This research takes one bus company's 12m long city bus (2.5m wide, 3.2m high) as the research object. The body frame finite element model is established in ANSYS, and the static analysis is carried on horizontal bending, limit twisting, emergency braking and urgent turning four kinds of typical working conditions. Through the analysis of the results, a body frame lightweight scheme is proposed. And then, the body frame which before and after lightweight is compared and analyzed in ANSYS. 2. THE BODY FRAME FINITE ELEMENT MODELING 2.1 Model simplification Monocoque bus body frame is steel welded together by all sorts of different section thin-walled complicated space truss structure, outer including a large number of skin, and some auxiliary load bearing parts. The outer skin and auxiliary load bearing parts have little influence on the stress distribution and deformation distribution of body frame, but have a great influence on the accuracy of finite element analysis. Therefore, we need to appropriately simplify the model [2-4]: Ignore the auxiliary load bearing parts which have a little influence on bus body construction, such as vehicle doors, seats, interior decoration, wood flooring, etc; Ignore the strengthening effect of skin; The curved beam is simplified to straight beam; Merger the components nodes which have a very close distance, avoiding appears morbid equation in calculation; Smooth components surface and omit process holes; Simplify the cross section shape. 51