Lightweight optimization of bus frame structure considering rollover safety

Abstract

The transit bus is an important part of public transportation, while in a bus rollover accident the deforming superstructure seriously threatens the lives of the passengers and the crew in the bus. Thus, bus rollover safety and how to design a bus superstructure with a good stiffness of vehicle frame is an important task for bus manufacturers. The legislation regulation number 66 of the Economic Commission for Europe (ECE R66) of bus rollover protection has been enforced for bus rollover protection. Strengthening the bus frame to maintain survivor space and reduce occupant injury is necessary following the issue of ECE R66, whilst lightweight structures in bus body design have also been highlighted. Therefore, this study presents a lightweight optimization considering the bus rollover crashworthiness design. In this study, the side wall section, and the roof section of bus frame are analyzed based on energy absorption ability in order to specify the design variables. With the aim of improving both the deformation of the bus frame versus the vehicle’s survivor space and the body skeleton density of the vehicle structure, optimization is performed by LS-OPT with the successive respond surface method (SRSM), where LS-DYNA is used as the FE solver. An optimal vehicle model was obtained with a lightweight structure and crashworthiness following ECE R66. The findings could be used by automobile manufacturers in a new design of bus superstructure, incorporating the rollover safety legislation and lightweight optimization.