- 期刊
應用歐規ECE R66等效認證方法進行大客車翻覆強度之探討
Numerical Simulation of a Rollover Test on an Intact Bus as an Equivalent Approval Method
摘要
大客車具有高乘載之能力的公路交通工具，倘若發生重大事故，其乘員損傷將極爲嚴重性。大客車於事故發生翻覆時，損壞常發生於結構焊接處，爲了乘員之安全，在進行大客車上層結構設計時應考量焊接對翻覆強度之影響，已往數值分析時，焊接處多以理想化之共點接合方式處理，並無考慮實際焊接效應而與實際狀況不符。 本文以大客車之翻覆強度爲研究對象，採用非線性軟體LS-DYNA爲分析工具。採用填角焊與對接之焊接失效準則，並比較理想化共點方式與考量焊接效應之數值模擬結果之差異，此外，依據歐規ECER66建立大客車整車翻覆等效認證方法之數值模擬環境，並以歐洲某型大客車爲研究對象進行共點與考慮焊接失效之影響，並驗核是否滿足歐規ECER66之要求，結果顯示理想化之共點接合有限單元模型，其結構能量之傳遞持續性較佳，而考慮焊接效應之有限單元模型由於考量失效準則，其力學行爲與實際狀況較接近。本文所建立之大客車翻覆等效數值認證方法，由於考量焊接失效，較符合實際之狀況，應能提供大客車車廠製造設計之使用。
並列摘要
Buses have a high transportation loading capacity on the road. When a major accident occurs, the passengers can be seriously injured. In a bus rollover accident, the damage usually occurs in a weld zone. For passenger safety, the design of the superstructure of a bus should particularly consider weld zones due to the strength of a bus rollover accident. In previous numerical analyses, the weld zones were often idealistically assembled in a concurrent way; however, those analyses did not account for the effects of welding. Approval for rollover crashworthiness, in accordance with regulation number 66 of the Economic Commission for Europe (ECE R66), is a requirement for all newly registered coaches and buses sold in Taiwan. This regulation requires that a minimum passenger survival space be met during a rollover. Since rollover tests with real vehicle structures are costly, computer-aided crash simulation, which is becoming increasingly efficient and affordable, will play a more significant role in the approval for crashworthiness in the near future. This research adopted an equivalent approval method for computer simulation of an ECE R66 rollover test on a complete vehicle and coupled it with the nonlinear finite element software LS-DYNA to study the rollover strength of a double-deck bus, for which both ductility and brittleness failures of Spot and Butt welds were considered. In LS-DYNA the capacity of a weld is based on rigid body dynamics, wherein each weld is defined by a set of nodal points which move rigidly with six degrees of freedom until the failure criteria are satisfied. The numerical results of an extrusion simulation analysis of the structure of a bus frame showed a model which considered that the welding effects are better than an idealistic assembly in a joint manner. The welds at the bottom of the vehicle did not fail; moreover, the simulation and experimental results matched. The study demonstrated that the finite element model with ideal joints continuously absorbed energy during the rollover because the joints, being stiffer, did not fail. When considering the welding effect in conjunction with the failure criteria, the behavior of the bus in the simulation was much closer to the behavior of an actual vehicle. This report can provide guidance for bus manufacturers in both the design process and simulation.