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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/43921

Title: IGA用於船體局部結構強度與挫曲分析
Strength and buckling analysis of local ship structure using the IGA method
Authors: Tsou, Wen-Huai
鄒文懷
Contributors: NTOU:Department of Systems Engineering and Naval Architecture
國立臺灣海洋大學:系統工程暨造船學系
Keywords: 等參數幾何分析;加強板;造船工業
isogeometric analysis;NURBS;Mindlin plate;stiffened plate;Naval Architecture
Date: 2016
Issue Date: 2017-11-02T09:04:50Z
Abstract: 一般船舶設計的過程中,需要計算船舶在不同海況以及航行狀態下,對船體所造成的阻力以及螺槳推進效率,上述情況也會對船體結構造成扭轉(torsion)、彎曲(bending)以及剪力(shear)等受力狀態。而為達成最小阻力之目標,船型會依據船殼周圍流場的情況來做幾何優化設計。在2008年由Wolfgang A. Wall等人[11]提出利用non-uniform rational B-spline function(NURBS)為形函數的isogeometric analysis建立一套結構幾何形狀優化流程。後續有人提出利用NURBS建立船體模型以改善傳統的網格法幾何形狀近似不精確的問題,並利用BEM-IGA來計算船體阻力[12][13]。而IGA除了幾何形狀近似精確的優點外,由於直接以建立幾何的方程式作為形函數,因此從CAD模型轉換為數值模型的過程較傳統網格法簡單且快速。 在一般網格法的分析流程中,由於建立幾何所使用的形函數(B-spline),與物理近似所使用的形函數不同,因此在匯入模型至分析程式後,會需要再依照形函數需求,重新劃分網格,而此網格劃分的步驟往往會佔總分析時間的80%左右[1]。IGA直接使用B-spline近似物理場,因此可以省去網格劃分的步驟,且B-spline為高階以及高連續性的方程式,其可以建立出精確的高階曲面形狀,並適合用於接觸問題等需要多次微分的分析。 本研究利用上述IGA的優點,建立一套針對船體結構的完整分析流程,並依照此流程建立分析程式。在模型匯入程式後,即可以自動劃分網格並完成分析,且依照本文建立數值模型的流程,將可以自動連接結構單元(板單元以及樑單元)的自由度,而不需要任何特殊的連接處理方式。在完成數個標準的驗證問題後,將此驗證過的程式應用在局部船體結構分析,並與船體結構設計法規連結。此程式未來除了可用於全船結構分析外,也適合應用於船體碰撞或與無網格法耦合,分析船體開裂等問題。
General ship design requires wide range of analyses from the loading type, efficiency, and resistance to structural strength for torsion, bending and shear. The ship geometry is usually optimized based on the surrounding fluid field to generate the shape with least resistance. Therefore, the Non-uniform rational basis functions (NURBS) are usually employed for the construction of smooth ship hull surface instead of using traditional mesh-based shape approximation [11-13]. Also the isogeometric analysis (IGA) can obtain the numerical model easier and faster than the traditional FEM in ship structural analysis. In analysis process of mesh-based methods, we use different shape functions to build model and approximate the physical field. After we imported the model into analysis program, we need to regenerate the mesh according to the requirement of the shape function. The mesh-generation procedure usually consumes about 80% of the total analysis time [1]. The IGA directly uses B-spline as the shape function, so it can skip mesh generation. Because B-spline is a high order and high continuity function, it can build exact high order surface and analyze contact problems which need more differential time. In this research, we use the advantage of the IGA to build a complete analyzing procedure for the ship structural analysis. We also build the analysis program according to the analysis procedure. After the model is imported into the program, it can generate the mesh and finish the analysis automatically. According to the procedure of building the numerical model, the program could connect the degree of freedom of the structural element (shell element and beam element) without any specifically connecting method. After we complete the verification of the developed program with several benchmark problems, we apply this program to analyze the local ship structure according to the structural design rule. In addition to the whole ship structural analysis, this program is also suitable for ship collision problem or coupling with the meshfree method for ship breaking problem in the future.
URI: http://ethesys.lib.ntou.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=G0010351027.id
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/43921
Appears in Collections:[系統工程暨造船學系] 博碩士論文

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