CAD模型之Fillet與Boss混合式實體網格建構研究

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/72420

Title:	CAD模型之Fillet與Boss混合式實體網格建構研究
Authors:	林子勤;Lin,Zih-Chin
Contributors:	機械工程學系
Keywords:	模流分析;實體網格;四面體網格;稜鏡形網格;六面體網格;Mold flow analysis;Solid mesh;Tetrahedron mesh;Prism mesh;Hexahedron mesh;Fillet;Boss
Date:	2016-08-01
Issue Date:	2016-10-13 14:54:27 (UTC+8)
Publisher:	國立中央大學
Abstract:	實體網格對於模流分析結果的正確性影響重大，目前常用於數值分析的三種實體網格分別為四面體網格、稜鏡形網格及六面體網格。四面體網格的優點為可利用自動化技術快速建實體構網格；缺點則為網格品質不一定優良及不易控制網格層數。稜鏡形和六面體網格的優點為網格品質較四面體網格更佳；缺點則為雖可利用自動化技術快速建構實體網格，但產生的網格品質卻不一定優良。為了建構品質優良的稜鏡形和六面體網格，目前仍須仰賴人工的方式來建構實體網格。本研究利用人工建構實體網格的方式，針對CAD模型中的Fillet(圓角)與Boss特徵，研究建構稜鏡形與六面體網格的方法。Fillet特徵部分，由於實體網格的形狀會受Fillet曲面影響而產生形變使網格品質略差，為了改善Fillet處的網格品質，因此使用本實驗室所開發的六種圓角網格樣板概念於Fillet處建構實體網格，原理為將六面體網格的形狀變為與Fillet相似，其中圓角網格樣板的網格數量與大小可依照實際的情況調整。Boss特徵則分為Tube和Rib二部分，建構Boss實體網格的原則為沿著Tube和Rib的厚度方向建構稜鏡形和六面體網格，目的為控制厚度方向的網格層數，因為厚度方向的網格層數會影響模流分析結果。最後本研究將於實際CAD模型範例中建構實體網格，並與利用現有技術建構的實體網格比較網格品質與模流分析結果，以顯示本研究與現有技術之差異，而本研究的成果於未來中亦會用於協助發展Fillet與Boss特徵的實體網格建構自動化之演算法。;The quality of solid meshes affects the accuracy of the analysis considerably in mold flow analysis. Three kinds of solid meshes typically used in numerical analysis are: tetrahedron, prism, and hexahedron meshes. The advantage of tetrahedron meshes is that the meshes can be generated automatically. However, its disadvantages are that the mesh quality may not be satisfied and it is difficult to control the number of mesh layers. The advantage of prism and hexahedron meshes is that the mesh quality is much better than that of tetrahedron meshes. But, the disadvantage is that it is difficult to generate these types of meshes automatically. To generate prism and hexahedron meshes of high quality, it still relies on manual work to plan and edit the solid meshes. The purpose of this study is to analyze the method of solid mesh generation and propose a framework for generating prism and hexahedron meshes manually, especially for CAD models with fillets and bosses. When fillets appear, the shape of the solid meshes is usually deformed owing to long and narrow shape of the fillets. To improve the mesh quality for CAD models with fillets, we developed six kinds of mesh templates for fillets. The principle of the proposed mesh templates is to generate hexahedron meshes for all kinds of fillets. The number and size of meshes on each template can be adjusted in accordance with actual shape and size of fillets. As for bosses, they can be divided into two parts: tube and rib. The principle of solid mesh generation for bosses is to generate prism and/or hexahedron meshes along the direction of the thickness, and control the mesh layer along that direction. Finally, several CAD models are employed to generate prism and hexahedron meshes by using the proposed mesh generation method. A comparison of the meshes obtained using the proposed method and current technique is provided also. The proposed mesh generation concept can be used for developing automatic solid mesh generation algorithm for prism and hexahedron meshes in the future.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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