- 學位論文
大客車車體結構碰撞分析與耐撞性之研究
Collision Analysis and Crashworthiness Study for Bus Body Structure
摘要
近年來大客車事故頻傳，不只是翻覆意外，碰撞事故也不少。對於大客車車體結構安全強度國內尚無完整的相關法規規定，而國內多數製造廠商因成本考量簡化了大量的補強結構，因此結構強度的不足成為發生事故的原因之一。 本文首先針對一般大客車骨架結構形式進行耐撞性分析，對業界常用的六種骨架進行有限元分析比較其優缺點，同時研究模型中網格尺寸、厚度積分點、沙漏能控制及局部網格細化等收斂性分析，為後續整車骨架有限元模型的建立提供參考。接著，引用已滿足翻覆安全強度之大客車車體結構設計並重新繪製，利用有限元素法進行碰撞模擬分析，其中包括正面碰撞，側面碰撞及後部碰撞，碰撞場景配置則參考法規FMVSS 208、214、301。從初步的模擬分析，瞭解大客車整體骨架的變形過程及主要緩衝吸能構件的的變形情況，發現大客車車體結構強度耐撞性能不足，導致乘客殘留空間被侵犯，表示原始大客車車體結構強度需要改善並決定需要進行補強的部位。補強方式以不同幾何骨架結構形式、改變骨架排列位置及增加補強結構件等方式分別對保險桿、車頂及底層結構重新進行強度設計與分析，找出較為合適的結構設計形式，去改善其能量的吸收能力，以提升耐撞性能。 綜合以上種種設計型式與補強之考量，將大客車做適當的結構改良設計，反覆進行碰撞分析，保險桿部分以耦合型式可獲得最小加速度峰值16.4g，DIY型式設計可獲得較好能量吸收，兩者皆有最小位移約1500mm；車頂經改良後，可將衝擊帶往車身中段，避免變形集中於車頭，且變形不影響乘客殘留空間；底層結構以斜撐方式進行補強，增加側牆整體強度，減少乘客殘留空間的侵犯，車體傾斜及骨架變形皆獲得改善，因此研判本文改善方式可供業者做為大客車車體結構安全強度設計之參考依據。
並列摘要
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.