臺灣博碩士論文加值系統

本文旨在利用理論及數值方法，探討鋁合金高速船之艏結構在航行時與其他結構如海洋平台、作業船隻、或是暗礁發生高速碰撞時之抗撞安全性評估。
在數值分析方面，本文採用有限元素套裝程式LS-DYNA，先對船艏結構基本元件(圓管、方柱、十字斷面柱)之壓潰行為進行數值分析，進而對複雜構件、簡化之箱型船艏結構以及真正之船艏結構的碰撞壓潰行為加以探討，除了瞭解整個壓潰過程及抗壓強度外，亦供為理論分析結果之比較驗證。
在理論分析方面，本文建立了艏結構元件受軸向碰撞衝擊時之漸進式挫曲理論分析模式。不僅推導艏結構元件的挫曲理論預估式，結構元件L形、X形(十字形)、T形元件的理論模型之正確性亦直接或間接地獲證，此外，材料是基於完全剛塑性(rigid plastic)的假設，並考慮了應變率對結構元件壓潰力的影響。
在船艏結構整體的抗壓能力預估方面，本文將Yang 與 Caldwell 以及 Ohtsubo的理論基礎加以改良。將複雜結構分割成基本元件的組合，以理論預估式計算其抗壓能力，並與LS-DYNA計算之結果比較，同時探討材質或應變率以及各種參數對複雜結構抗壓能力的影響；接著建立一箱型多層結構，分析其壓潰行為以及各肋骨(frame)之間的壓潰順序。最後將Hagiwara所建立之船艏的模型分割成L形、┼形、T形元件的組成，並將各元件所吸收的能量疊加，可得整個船艏結構的抗壓能力，並與LS-DYNA之結果相比較。在了解船艏結構的壓潰反應之後，本文更進一步建立兩船碰撞的分析例，利用能量不滅以及牛頓運動定理計算船艏與船側碰撞時，外力與變形之間的關係，在利用LS-DYNA驗證之後，並進一步討論船艏結構在不同條件下發生碰撞時的安全性。

The purpose of this paper is to present a basis for the estimation of collision forces between aluminium-constructed high-speed ships and other structures, like offshore structures, vessels, and ground by theoretical and numerical methods.
In respect of numerical investigation, the ship cross-section is considered as assemblage of basic elements, and crushing behavior of basic elements is analyzed by using finite element software LS-DYNA. In addition, composite structure, simplified bow structure, and real bow structure are also modeled to verify the validity of theoretical prediction.
In respect of theoretical investigation, a rigid-plastic material is assumed. Progressive buckling model of bow structural elements due to axially impact load was studied and compared with numerical calculation results. And the validity of the formulas of L shape, T shape, and ┼ shape is proved. By changing the material property of theoretical model, the difference between aluminum alloy and mild steel in impact collapse mode was compared. Effects of strain-rate on the crushing of structure are also included.
The Yang & Caldwell''s technique as well as Ohtsubo''s technique of deriving the simplified equation of mean crushing force is used and applied to the composite structures. The composite structure is divided into simple elements of L shape, T shape, and ┼ shape. In the same way, simplified bow structure and Hagiwara''s real bow structure models are established numerically and theoretically. The theoretical prediction and the numerical results are also compared. On the basis of crushing behavior of bow structure, furthermore, the high-energy collision between bow and side structures is modeled with the assumption of energy conservation and then the force-indention relation is established. The paper concludes with the crashworthiness of collision between two ships.

目 錄
頁次
摘要…………………………………………………………… i
表目錄 ………………………………………………………… v
圖目錄 ………………………………………………………… vi
第一章 緒論 ………………………………………………… 1
1.1問題陳述 ………………………………………………… 1
1.2 文獻回顧 ………………………………………………… 2
1.3 論文之架構 ……………………………………………… 3
第二章 船艏壓潰反應數值分析 ……………………… 5
2.1 變形場與運動方程式 ( deformation field & equation of motion ) …………………………………………………… 6
2.2 有限元素方程式 ( finite element discretization ) ……………………………………………………………… 7
2.3 時間積分 ( time integration ) ……………………… 8
2.4 接觸演算法 ( contact algorithms) …………………… 11
2.5 船艏結構基本元件之數值解析 …………………………… 11
2.5.1 在平板挫曲解析例之驗證 ………………………………… 11
2.5.2 圓形薄管之壓潰分析 ……………………………………… 16
2.5.3 方形斷面之薄管壓潰分析 ……………………………… 23
2.5.4 十字形斷面之薄柱壓潰分析 ………………………… 33
2.5.5 時間分割( time increment ) 對數值解析精確度的影響 ……………………………………………………………… 40
2.5.6 壓潰速度與應變率效應 ( crushing velocity & strain-rate effect ) …………………………………………………… 41
2.5.7 結構初始不良度的影響 ( effect of structure initial imperfection ) ………………………………………… 42
2.6 複雜構件壓潰之數值解析 ………………………………… 43
2.7 簡化之箱型船艏結構壓潰之數值解析 ……………………… 50
2.8 船艏結構壓潰之數值解析 ……………………………… 54
2.9 船艏結構與船側結構碰撞之數值解析 ……………………… 62
第三章 船艏結構之抗壓理論 …………………………………… 70
3.1 緒論 …………………………………………………………… 71
3.1.1名詞解釋 …………………………………………………… 71
3.1.2 理論推導方式簡介 ………………………………………… 72
3.2 圓管之壓潰機制分析 (crushing mechanics of circular tube) …… …………………………………………………… 74
3.2.1 圓管之靜態壓潰分析(static axial crushing of a circular tube) ……………………………………………………… 74
3.2.2圓管之動態壓潰分析(dynamic axial crushing of a circular tube) ………………………………………………………… 76
3.3 方形斷面空心管壓潰機制分析 (crushing mechanics of a square tube) ……………………………………………………… 80
3.3.1方管之靜態壓潰分析(static axial crushing of a square tube) ………………………………………………………………… 80
3.3.2方管之動態壓潰分析(dynamic axial crushing of a square tube) ……………………………………………………………… 90
3.4 L形斷面柱壓潰機制分析(crushing mechanics of L column ) ……………………………………………………………… 91
3.5 T形斷面柱壓潰機制分析 (crushing mechanics of T column ) ………………………………………………………………… 96
3.6 十字形斷面柱壓潰機制分析(crushing mechanics of cruciform column) …………………………………………………… 98
3.7 田字形結構壓潰機制分析(crushing mechanics of composite structure ) ……………………………………………… 101
3.8 箱型多層艏結構壓潰機制分析(crushing mechanics of simplified bow structure)………………………………………… 105
3.9 Hagiwara model壓潰機制分析 (crushing mechanics of Hagiwara model) …………………………………………………………… 108
3.10 兩船碰撞機制分析( crushing mechanics of high energy collision)…………………………………………………… 109
第四章 結論與展望 ……………………………………………… 111
4.1 綜合結論 ……………………………………………………… 111
4.2 未來研究之展望 ……………………………………………… 111
參考文獻 …………………………………………………………… 113

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