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Passenger "Sleeper Bus" Structure, an Optimization Study using Finite Element Analysis
ISSN: 0148-7191, e-ISSN: 2688-3627
Published November 21, 2019 by SAE International in United States
Event: NuGen Summit
ABSTRACT Sleeper buses are increasingly used as connectivity between cities and remote areas with sleeping comfort for passengers. During the normal operation, the bus body is subjected to several loads, external loads from the road (i.e. crossing over a speed bump, breaking & cornering). Moreover, there is a substantial possibility that these loads may lead to a structural failure. Hence, it is necessary to determine stresses occurred in the bus body to ensure its integrity under these driving scenarios. During the accident, rollover/front/rear/side impact, energy absorbing capacity of bus body structure is crucial for safety of passengers. The objective of this study is to reduce weight of bus structure while maintaining cost & safety as constraint. 3D Model prepared in NX and finite element model created in hypermesh ,LS-dyna/optistruct used as solver and post processing done in hyperview. In this study, fully loaded bus with passengers as well as maximum language mass, considered. The present study is based on the finite element analysis and design optimization of passenger sleeper bus. Number of iterations in stiffness Analysis, Modal Analysis, Rollover analysis and Front/Rear/Side impact conducted .During Impact analysis , survival space considered for passengers/driver/co-driver safety. It is observed that major scope to reduce weight is in bus floor structure. Other Bus Body structure parts are found to be in required limits. Weight savings up to 80Kg /Bus Structure ,were realized by this study . Bus Body structure found to meet the regulatory norms (AIS-031/052/119) in final iteration. ISMC Channels (IS2062) replaced by C-Channels of ST52.3 Material. Tubular structural member's specification constrained with in-house material inventory . Scope to reduce material on other structural parts i.e. sides,front,rear and roof is very limited due to impact energy absorption in case of accident. Regular body manufacturing process to be used with same tooling. During design & proto phase ,overall bus body weight increased which may affect the overall GVW as defined by OEM Chassis specification and passenger carrying capacity . Cost is another major constraint during this study. The baseline model is redesigned by changing the structural members thickness and adding material on weaker areas by introducing specific ribs so that the total weight of the bus is reduced. In Final iteration, Design optimized and challenges overcome by maintaining cost & safety constraint. Keywords-Optimization, Sleeper Bus, FEA