| Summary: | 碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 101 === Bus accidents have been frequent in recent years, including rollovers and crashes. Regulations on the strength of the bus body structure, however, are inadequate and incomplete. Most of the domestic bus body manufacturers have simplified the reinforcement of the bus body structure for the sake of lower costs, meanwhile the insufficient structural strength is exactly one of the major causes of bus accidents.
In this research, the crashworthiness analysis of the bus skeleton structure was given in the first place, where six most commonly seen bus skeletons were taken for finite element analysis to observe their good and bad. Meanwhile, for subsequent establishment of a finite element model of a whole bus skeleton, also conducted were convergence analyses of middle-sized meshes, thickness integration points, hourglass control, and local mesh refinement. And then, a body structure conformable to the rollover safety strength was taken as the basis for re-drawing the skeleton, for which a finite element method was used to analyze the simulated crashes, including frontal crash, side crash, and rear crash, and the crash scenario was built in accordance with the legal act FMVSS 208, 214 and 301. In the initial simulation analysis, the deformation of the entire bus body skeleton and the energy-absorbing cushioning components were observed, which revealed an inadequate crashworthiness strength of the bus body structure, that could lead to invasion of passengers'' residual space. The result suggests that the strength of the bus body structure needs to be improved and the spots in need of reinforcement should be identified. The reinforcement can be done by adding geometric skeletons, changing the skeleton''s aligning arrangement, adding reinforcement structural components to make the bumper, roof and bottom structure stronger in a better and tougher body structure, so that the body can be more capable of absorbing the impact from crashes to increase crashworthiness.
With all the design patterns and reinforcement considerations mentioned above, the bus body structure can be improved through repetitive crash tests and analyses for a better design, and if the bumper is made a coupling pattern, it will be able to acquire the minimum acceleration peak value of 16.4g, plus the DIY design pattern that can produce a better energy absorption capacity, making a minimum displacement of approximately 1500mm. Improved design of the car roof can distribute the crash impact to the middle part of the car body to avoid too much concentration of deformation on the car head, thus the passengers'' residual space won''t be much affected. The bottom structure can be reinforced with diagonal brace to increase the overall strength of the sides and reduce the invasion of passengers'' residual space, so that the car boy tilting and skeleton deformation from crashes can be alleviated. Hopefully, the results of this study can provide helpful information to the car body designers and manufacturers for them to make better and safer buses.
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