模流分析(Mold flow analysis)是一種有限元素分析，在執行模流分析前，需將CAD模型轉換成實體網格(Solid mesh)，再賦與分析軟體計算。為提升分析之準確度，對CAD模型建構品質與精度較高的結構化網格是解決方案，但現今結構化網格主要以非自動化方式建立。本研究之目的是發展應用於薄殼CAD模型之薄殼本體體積分解演算法，藉以輔助結構化網格之建立。本演算法自動化將薄殼本體分解為規則區塊之組合，各獨立的區塊表示自薄殼本體分解的實際體積。區塊是以封閉輪廓的方式記錄，能提供建立結構化網格之輔助資訊，區塊間亦記錄關聯性，以確保網格間正確接合。本研究發展之演算法能分解坐落凸起特徵之薄殼本體，亦拓展應用性至具階梯層結構或多種複雜交界結構之薄殼本體。對於分解坐落凸起特徵之薄殼本體，結合凸起特徵辨識技術。而對於分解具階梯層結構或多種複雜交界結構之薄殼本體，則將薄殼本體分離為多個區域獨立分解，再記錄區域間的對應資料。本研究發展自動化分解薄殼本體為規則區塊之技術，藉以提供建立結構化網格之資料。

Mold flow analysis is a kind of finite element analysis. Before performing mold flow analysis, the CAD model needs to be converted into solid meshes and then assigned to the analysis software for calculation. In order to improve the accuracy of the analysis, it is a solution to construct structured meshes with high quality and accuracy for the CAD model, but nowadays the structured mesh is mainly established in a non-automatic way. The purpose of this research is to develop a volume decomposition algorithm for the thin shell body of thin shell CAD models, so as to assist the establishment of structured mesh. The algorithm automatically decomposes the thin shell body into a combination of regular blocks, each of which represents the actual volume decomposed from the thin shell body. Blocks are recorded in the form of closed regions, which can provide auxiliary information for building structured meshes, and the associations between blocks are also recorded to ensure proper connection between meshes. The algorithm developed in this study can decompose the thin shell bodies with protrusion features, and also expand the applicability to the thin shell bodies with stepped structures or various complex transition structures. For the decomposition of the thin shell body with protrusion features, the proposed method combines with the feature recognition technology. For the decomposition of the thin shell body with stepped structures or various complex transition structures, the proposed method is to divide the thin shell body into multiple areas and then decomposed them independently. The main purpose of this study is to develop the enhanced algorithm of automatically decomposing the thin shell body into regular blocks, so as to provide data for building structured meshes.

[1] S. S. Liu and R. Gadh, "Automatic hexahedral mesh generation by recursive convex and swept volume decomposition," 6th International Meshing Roundtable, Sandia National Laboratories, pp. 217-231, 1997.
[2] Y. Lu, R. Gadha and T. J. Tautges, "Feature based hex meshing methodology: feature recognition and volume," Computer-Aided Design, vol. 33, no. 3, pp. 221-232, 2001.
[3] D. R. White, S. Saigal and S. J. Owen, "CCSweep: automatic decomposition of multi-sweep volumes," Engineering with Computers, vol. 20, pp. 222-236, 2004.
[4] B. Jüttler, M. Kapla, D. M. Nguyen, Q. Pan and M. Pauley, "Isogeometric Segmentation: The case of contractible solids without non-convex edges," Computer-Aided Design, vol. 57, pp. 74-90, December 2014.
[5] J. E. Makem, C. G. Armstrong and T. T. Robinson, "Automatic decomposition and efficient semi-structured meshing of complex solids," Engineering with Computers, vol. 57, pp. 345-361, 2014.
[6] L. Sun, C. M. Tierney, C. G. Armstrong and T. T. Robinson, "Automatic decomposition of complex thin walled CAD models for hexahedral dominant meshing," Procedia Engineering, vol. 163, pp. 225-237, 2016.
[7] L. Sun, C. M. Tierney, C. G. Armstrong and T. T. Robinson, "An enhanced approach to automatic decomposition of thin-walled components for hexahedral-dominant meshing," Engineering with Computers, vol. 34, no. 3, pp. 431-447, 2018.
[8] B. Lecallard, C. M. Tierney and T. T. Robinson, "Automatic hexahedral-dominant meshing for decomposed," Computer-Aided Design & Applications, vol. 16, no. 5, pp. 846-863, 2019.
[9] J. Y. Lai, P. P. Song, Pradiktio Putrayudanto, T. Y. Wu, Y. C. Tsai, M. H. Huang, and C. H. Hsu, "Decomposition of protrusion features on thin-shell parts for mold flow analysis," Engineering with Computers, 2022.
[10] 吳家瑋，「薄殼零件薄殼本體之結構化實體網格自動建構技術發展」， 國立中央大學，碩士論文，2020
[11] 周子耀，「薄殼CAD模型之薄殼本體體積分解技術發展」，國立中央大學，碩士論文，2021
[12] Rhinoceros. [Online]. Available: http://www.rhino3d.com. [Accessed 6 June 2022].
[13] OpenNURBS. [Online]. Available: http://www.rhino3d.com/tw/opennurbs. [Accessed 6 June 2022].
[14] B-rep structure. [Online]. Available: http://wiki.mcneel.com/developer/brepstructure. [Accessed 6 June 2022].
[15] 王明暄，「應用於模流分析之CAD模型特徵辨識與實體網格品質提升之研究」，國立中央大學，博士論文，2017
[16] J. Y. Lai, C. Wong, T. T. Huynh, M. H. Wang, C. H. Hsu, Y. C. Tsai and C. Y Huang, "Small blend suppression from B-rep models in computer-aided engineering analysis," Journal of the Chinese Institute of Engineers, vol. 39, no. 6, pp. 735-745, 2016.
[17] Himawan Wibhisana, "Development of chamfer recognition technology for CAD model," National Central University, Master Thesis, 2017.
[18] J. Y. Lai, M. H. Wang, Z. W. You, Y. K. Chiu, C. H. Hsu, Y. C. Tsai and C. Y. Huang, "Recognition of virtual loops on 3D CAD models based on the B-rep model," vol. 32, no. 4, pp. 593-606, 2016.
[19] J. Y. Lai, P. P. Song, Y. C. Tsai and C. H. Hsu, "Automatic hole recognition and classification for a set of B-rep models representing an injection mold," International Journal of Mechanical Engineering and Robotics Research, vol. 9, no. 8, pp. 1189-1197, 2020.
[20] Pradiktio Putrayudanto, "Face types recognition for thin-shell CAD models," National Central University, Master Thesis, 2021.
[21] 宋培溥，「應用於模流分析之薄殼元件CAD模型特徵辨識與分解技術發展」，國立中央大學，博士論文，2021
[22] 吳添瑜，「B-rep模型凸起特徵辨識及分解技術發展」，國立中央大學， 碩士論文，2022
[23] Moldex3D. [Online]. Available: http://www.moldex3d.com/en/. [Accessed 6 June 2022].
[24] 黃弈中，「薄殼CAD模型之內外面類型辨識技術發展」，國立中央大學，碩士論文，2022
[25] J. Y. Lai, J. W. Wu, P. P. Song, T. Y. Chou, Y. C. Tsai and C. H. Hsu, "Hybrid mesh generation for the thin shell of thin-shell plastic parts for mold flow analysis," Engineering with Computers, 2021.
[26] 王培懿，「CAD模型混接面、虛擬環及孔洞辨識技術發展」，國立中央大學，碩士論文，2022