Develop and Apply the Adaptive Meshfree Method for the Modeling of Ship-Hull-Crack Propagation

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Project title

Code/計畫編號

MOST109-2221-E019-021

Translated Name/計畫中文名

發展與使用調適無網格法進行船殼裂縫行為之模擬

Project Coordinator/計畫主持人

Pai-Chen Guan

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Systems Engineering and Naval Architecture

Website

https://www.grb.gov.tw/search/planDetail?id=13539093

Year

2020

Start date/計畫起

01-08-2020

Expected Completion/計畫迄

31-07-2021

Bugetid/研究經費

884千元

ResearchField/研究領域

機械工程

本實驗室近幾年著重在實用性的計算模擬方法開發，並應用在船體結構分析相關，且有限元素法無法解決的問題上。本研究的目標在開發、撰寫並使用新型的數值方法分析船體結構裂縫成長的行為。傳統的結構分析多仰賴於有限元素法(FEM)，但有限元素法有著強烈的網格依賴性，無法處理任意裂縫擴展的問題，一般船體結構在建模上也非常耗時。而最近幾年開始發展的近場動力學與等參幾何分析法，剛剛好可以滿足快速裂縫模擬與船板快速建模分析的兩個特性。所以我們提出了使用調適耦合等參幾何分析與近場動力學（IGA-PD）。使用PD來描述裂縫區域，其他沒有裂紋的區域使用IGA方法模擬，來加快計算速度並確保幾何形狀的精確性。在過去的研究中，我們已經開發了一種耦合等參幾何分析與近場動力學（IGA-PD）方法，已經應用於潛艦外殼的破裂情況模擬，未來可專門探討動態裂縫問題。而在IGA-PD耦合區域中，我們測試了Penalty方法和Nitsche’s方法的適用性。對於Penalty方法，我們引入了假想形函數來內插PD位移，同樣地，在Nitsche’s方法中，計算出PD的應力張量。除此之外，為了改善傳統調適性網格需要在每一裂縫成長時，重新建立不同單元間的網格，使計算量大增，因此我們引入剪切IGA用來修剪每一次的IGA網格，在計算上我們僅需捨棄裂縫生成區域的局部IGA網格，並快速布置PD離散點即可。除此之外，和目前現有的近場動力學耦合方法相比，本方法具有無需迭代過程，不需使用重疊區域以及兩者的網格大小不限的優點，因此本方法能在同時保持幾何精準度與裂縫準確性下，大量減少計算成本。計畫的最終目標是模擬水下船體在航行時的可能損壞模式，包含裂縫、挫曲過程，船體的應力改變與裂縫成長過程。航行載重例如酬載、海流與衝擊波等。 My lab has been developing practical computational methods, which can be applied in the field of ship structural analysis. And solve the problems that cannot be analyzed by Finite Element Method (FEM). The objective of this research is to develop a novel numerical method that can efficiently deal with crack propagation problems on ship hull structure. Traditional structural analysis often relies on the finite element method (FEM). However, the mesh dependency of FEM usually cause difficulty when modeling crack propagations. The meshing process also causes tremendous workhour. On the other hand, two fast-developing methods, peridynamics (PD) and isogeometric analysis (IGA), can solve crack propagation and meshing efficiency issue with tremendous advantage over FEM. Therefore, we propose to adaptively couple these two method. The PD particles are used to deal with the crack region, and the IGA mesh is used to model the region without cracks. In the past two years, we have developed a simply coupled IGA-PD code. This code has been applied to pressure hull crack modeling and can be used to simulate crack propagation problems.For the coupling method, we have tested two coupling methods, which are penalty and Nitsche’s method, to learn how to couple particle type and mesh type of methods. When constructing the adaptive algorithm, we take advantage of the T-spline concept to truncate the IGA mesh and re-discretized the crack propagating domain with PD particles. This method can maintain accuracy and efficiency simultaneously without very tedious numerical treatment processes.The final goal is to apply this code to model the underwater vehicle and to capture its possible crack generation and propagation processes under explosion, buckling and design loading conditions.

Keyword(s)

裂縫
船體結構
近場動力學
等參幾何法
無網格法
耦合
水下載具
crack propagation
ship structure
peridynamics；
isogeometric analysis
meshfree method
coupling
underwater vehicle

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Develop and Apply the Adaptive Meshfree Method for the Modeling of Ship-Hull-Crack Propagation

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