Shock Response of Structure Subjected to Underwater Explosion

早期水下爆炸現象、爆震波傳遞以及結構受爆震衝擊後的動態反應等資料，必須靠昂貴且耗時的水下爆炸實驗才能獲得，進行破壞實驗的模型僅能使用一次，獲得的結果亦有限，常須進行多次破壞試驗才能取得足夠資訊，同時試驗模型與量測設備的費用以及場地之環境安全的維護成本也相當高。有效的水下爆炸數值分析方法，不但可以降低試驗的次數與開支，同時也能提昇預估水下爆炸對結構破壞的能力。近年來電腦軟硬體的快速發展，使得數值分析技術可取代大部份的實驗，而且合理的模型與有效的分析方法也可較實驗取得更多有用的資料。本文探討有限元素分析水下爆炸對結構爆震反應的特性及其應用，分成三個部份：(一)基本有限元素分析特性探討：本文將探討近距離爆炸所需建立全有限元素網格的數量控制，並找出適當模擬炸藥的多物質有限元素模型，針對不同分析目的選用不同的分析工具。(二)分析驗証：本文對水下爆炸的炸藥模型與水域網格對爆震波分析結果之影響進行基本研究，其次針對Ramajeyathilagam與Vendhan(2004)以探討水下背面為空氣的嵌板之近距離爆炸試驗模型進行有限元素分析，首先建立一個0.55m x 0.45m x 0.002m的嵌板與0.6m x 0.6m x 0.5m的水域模型， 行與文獻試驗相同爆炸條件的分析，以檢討本文分析模式的正確性。接著整理近年來對三種不同圓柱殼結構，分別是無加強環肋、外加強環肋及內加強環肋結構，本研究選擇接近潛艦比例之圓柱殼結構模型進行小模型水下爆炸對結構衝擊的數值分析與試驗研究。圓柱結構模型的長與直徑之比例取接近潛艦的長寬比，並且考慮具環向加強肋骨之圓柱殼結構狀況，以檢討有無環向加強肋骨，對於水下爆炸圓柱殼抗爆震能力之影響。(三) 應用問題的研究：探討傳統加強肋及不同金屬三明治結構，在遭受到水下爆炸中爆震波衝擊的動態分析，比較其動態反應。The underwater explosion phenomenon, shock wave and the dynamic response of the structures attacked by shock pressure could only be acquired by expansive and time-consuming experiments of underwater explosion in early days. The model of failure mode can only be used once and the available results are often limited; hence, it is necessary to conduct numerous experiments to acquire sufficient data while the costs of the experiment are extremely high. The effective numerical analysis method for underwater explosion can not only reduce the times and the cost of experiments but also improve the prediction abilities of the damage of structures to underwater explosion. Due to the rapid development of computation hardware recently, the application of numerical analysis technique may replace most experiments, and effective solution tools with reasonable models can obtains more usable information. The study was aimed at exploring the characteristics and its application of finite element analysis to the dynamic response of structures subjected to UNDEX. The study was contains three parts; the basic study on the foundmental characteristics of the FEM analysis the verifications and the applications. Firstly, the study explored the quantity control of finite element grids, and the reasonable model of explosive and choose different analytical methods depending on the analysis purposes. Secondly, the study conducted basic research is on the FE models of explosives for underwater explosion and the effects of mesh at water domain on the results of shock pressure. Then a plate model adopted from the experiment model of Ramajeyathilagam and Vendhan (2004) with water domain were established. The analysis results were compared with experiment results.The experimental and numerical studies of three different cylindrical shell structures were performed; which were un-stiffened cylindrical structure, outside cylindrical structure and inside cylindrical structure. The ratio of the experiment model of cylindrical structure is similar in length and width ration of submarine. Finally, the dynamic responses of the traditional stiffened plate structure and various types of sandwich structures attacked by the shock pressure in underwater explosion were conducted. From the results of the anti-shock performance between different types of structures were compared.摘要 I文摘要 III錄 IV目錄 VI目錄 IX一章 緒論 1.1 研究動機與目的 1 1.2 文獻回顧 5 1.2.1 解析法與試驗法 5 1.2.2 數值分析法 10 1.2.3 試驗與數值分析相結合 18二章 水下爆炸相關理論與現象描述 20 2.1 爆震波的壓力歷時變化 22 2.2 水下爆炸能量分佈 26 2.2.1 水面及水底邊界對衝擊波傳遞的影響 27 2.2.2 衝擊波作用於結構上的外力 32 2.3 LS/DYNA 程式的理論基礎與計算方法 33 2.3.1 波傳問題 35 2.4 流固耦合 38 2.4.1 ALE 演算法的特點 44 2.5 以雙漸進近似法(DAA)處理結構表面與爆震波的交互作用 45 2.5.1 結構浸水表面運動方程式 50 2.6 龍骨爆震因子 54 2.7 水下爆炸對結構衝擊波壓之簡易估算 56三章 炸藥模型及流體元素的網格探討 61 3.1 炸藥、水及空氣的材料模型 62 3.2 炸藥模型選定的使用 65 3.3 網格影響 85 3.4 小結 94四章 嵌板受近距離水下爆炸衝擊的損壞分析 96 4.1 水下爆炸衝擊壓力負荷 100 4.2 高速衝擊力對結構材料強度之影響 103 4.3 研究模型 106 4.3.1 爆炸狀況 107 4.3.2 有限元素分析 108 4.4 分析結果與討論 113 4.4.1 考慮主爆震波與次衝擊波的影響 113 4.5 小結 126五章 圓柱體爆震分析 128 5.1 有限水域內小劑量高靈敏度炸藥當量之修正 128 5.2 水下爆炸試驗安排 131 5.2.1 試驗材料模型 132 5.3 試驗爆炸距離及爆炸水深 141 5.3.1 試驗環境對量測結果的影響及量測值之修正 142 5.3.2 爆炸衝擊壓力量測結果之修正 144 5.3.3 修正後量測爆壓極值與經驗估算式計算結果的比較 148 5.4 數值分析 149 5.4.1 非對稱反應之調整 151 5.5 比較結果與討論 153 5.5.1 觀測距離= 210 cm 153 5.5.1.1加速度 153.5.1.2動態應變 161 5.5.2 觀測距離= 35 cm 163 5.6 小結 166六章 金屬三明治結構抗爆震能力比較 169 6.1 模型確認 170.2 研究模型 178.3 分析結果比較 181.3.1 加速度比較 181.3.2 位移量比較 187.3.3 能量比較 194.4 小結 198七章 結論 199.1 未來展望 205考文獻 20