金屬三明治結構之水下爆震

Abstract

過去水下爆炸現象以及結構受爆震衝擊後的動態反應等資料，必須靠昂貴且耗費時間的試驗才能獲得，此外，由於水下爆炸對於水下結構物衝擊的過程非常複雜，因此理論解析僅能適用於較簡化的結構模型之動態反應估算。近來由於電腦軟硬體快速發展，以致於合理且有效的數值分析技術可以比實驗更迅速取得許多有用的資料。傳統的船艦結構除特定目的油水艙採用雙層殼體外，一般採用單殼結構，近年來由於雷射電焊的精進，使肋骨較大的單層殼可考慮改成深度較小，重量較輕的三明治結構。本文對於不同夾心結構的三明治結構進行水下爆炸的爆震反應系列分析。在進行水下爆炸對結構物衝擊分析之前，先檢討分析模式與分析方法的可靠性，再進一步分析金屬三明治結構的爆震反應。 本文主要分為三部分，先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)以空氣為背壓的嵌板之近距離爆炸試驗模型進行有限元素分析，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，進行與文獻試驗相同爆炸條件的分析，以檢討本文分析方式的正確性。再次探討雙層殼體夾層內介質於水下爆炸衝擊雙層殼板的動態反應影響。最後進行相同重量不同結構夾心型態之金屬三明治結構，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。 於FEM數值分析過程，利用LS-DYNA程式中的ALE計算方式，來處理模型之水下爆炸衝擊、水域壓力變化與流固耦合關係。

In the past, the information of impact responses of structures subjected to underwater explosion (UNDEX) were obtained from extremely expansive ship shock experiments, it needs also very long time to prepare the test and to evaluate the test results. The phenomena of ship structure subjected underwater explosion are very complicated, the theoretical approaches are available only for strongly simplified model. Due to the improvement of the computer technologies recently, the numerical methods provide the capabilities to predicate complex UNDEX problems, and can get more detailed information. The traditional ship structures are single hulls in general, only for specified purpose, eq. water tank, oil tank etc, the double hulls are taken into consideration. Because of the development of laser welding technology and the reduce of its investment cost, the laser welding has been adopted by the ship yards world wide progressively. The metal sandwich structures have been proposed to replace the traditional single hull structure with deep stiffness. In this thesis, metal sandwich structures with different types of core structures were studied. In this thesis, the rectangular plate subjected underwater explosion were carried out by FE-method, First. The plate model (with length width thickness =0.55m 0.45m 0.002m) and water domain (with length width depth =0.6m 0.6m 0.5m) were adopted from the experiment model from Ramajeyathilagam & Vendhan (2004). The results from FE-models and experiment are compared to verify the accuracy of the FE-model. And the influence of the core medium of the double hulls on the impact response of the sandwich structure were examined. Finally, different type of sandwich structures with same mass subjected underwater explosion are performed to compared their impact response and to compare the anti-shock performance.