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研究生： 何馬維
Himawan Wibhisana
論文名稱： CAD模型之倒角特徵辨識技術發展
Development of Chamfer Recognition Technology for CAD Model
指導教授： 賴景義
Jiing-Yih Lai
口試委員:
學位類別： 碩士
Master
系所名稱： 工學院 - 機械工程學系
Department of Mechanical Engineering
論文出版年： 2017
畢業學年度： 105
語文別： 英文
論文頁數： 82
中文關鍵詞： CAD模型 、倒角辨識 、倒角
外文關鍵詞： CAD model, Chamfer recognition, Chamfer
相關次數： 點閱：23  下載：0 
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    • 在有限元素分析中，網格生成是不可或缺的。然而在將CAD模型轉換為網格時，會遇到的問題之一是CAD模型通常具有大量的特徵面，其中有許多是屬於過渡面。在網格生成過程中，在過渡面如混接面和倒角的周邊時常形成不良的網格。這些實體附近的網格，其尺寸通常比相鄰面的尺寸更小，導致較差的分析結果產生。在某些有限元分析中，可能需要簡化這些微小的過渡面，但在簡化之前，必須要先對這些過渡面進行辨識。本研究的目的是開發一基於B-rep模型來辨識CAD模型上的倒角。包括以下步驟：輸入B-rep模型，候選倒角的辨識，分類候選倒角的方法與輸出倒角資訊。本研究所提出的演算法可識別三種倒角：平面倒角，頂點混合倒角和表面倒角。最後利用五十個CAD模型來驗證倒角識別算法的可行性。

    In finite element analysis, mesh generation is an indispensable operation. However, one of the problems encountered when converting Computer-Aided Design (CAD) models into meshes is that CAD models often feature a large number of faces, many of which are transition faces. In the mesh generating process, poor meshes can easily be formed around the transition faces, including blend faces and chamfers. The mesh size near these entities is usually smaller han that of adjacent faces, resulting in poor analysis results. In some finite element analysis, it might be necessary to suppress such tiny transition faces. However, they should be recognized first. The purpose of this study is to develop an algorithm to recognize chamfers on a CAD model based on the understanding of a boundary representation (B-rep) model. It includes the following main operations: input B-rep model, identification of candidate chamfers, methods to classify candidate chamfers, and output chamfer data. Three types of chamfers can be recognized by the proposed method: plane chamfer, vertex blend chamfer and surface chamfer. Fifty CAD models are presented to demonstrate the feasibility of the proposed chamfer recognition algorithm.

    Abstract I Acknowledgement II Contents III List of Figures V List of Table VII Chapter 1 Introduction 1 1.1 Foreword 1 1.2 Literature Review 3 1.3 Research Purposes and Methods 5 1.3.1 Research Purposes 5 1.3.2 Research Methods 6 1.4 Organization of Thesis 8 Chapter 2 Fundamental of Transition Faces Recognition 9 2.1 Introduction to Transition Faces 9 2.1.1 Classification of Transition faces 9 2.1.2 Terms Used in Recognition of Chamfers 16 2.2 Introduction to B-rep Data Structure 18 2.3 Introduction to Preliminary Function 20 2.3.1 Edge AAG 20 2.3.2 Face AAG 22 2.4 Importance of Chamfer Recognition Algorithm 25 Chapter 3 Chamfer Recognition Algorithm 31 3.1 Introduction 31 3.2 Overview of the Proposed Chamfer Recognition Algorithm 31 3.3 Identification of candidate chamfer 32 3.3.1 Primary Edges 32 3.3.2 Curvature Direction 38 3.3.3 Face Angle 41 3.3.4 Support Faces 41 3.4 Method to Classify Candidate Chamfers 41 Chapter 4 Results and Discussion 48 4.1 Introduction 48 4.2 Validating Methods 48 4.2.1 Operational procedure of the proposed algorithm 48 4.2.2 Operational procedures of CADdoctor 49 4.3 Results and discussion 54 Chapter 5 Conclusion and Future Study 67 5.1 Conclusion 67 5.2 Future study 68 References 69

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