金屬成形模擬有限元素網格重建自動化

Automation of Finite Element Remeshing for Metal Forming Simulation

鄭榮和(Jung-Ho Chen) ； 廖建中(Chen-Chung Liao)

《中國航空太空學會學刊》 27卷4期 (1995/12) Pp. 329-341

https://doi.org/10.6124/TAASRC.199512_27(4).06

摘要

有限元素模擬金屬成形的問題，最大的困擾在於分析過程中，網格會逐漸的扭曲。而嚴重的扭曲會影響分析結果的準確性，因此，必需在適當的時候，進行網格重建的工作，以產生較爲勻和之新網格繼續分析。由於網格重建的工作相當的煩瑣且容易出錯，而由人爲檢查網格的扭曲程度，不但不可靠而且可能經常在網絡已不堪使用時，尚未被發現而浪費很多無謂的分析時間或電腦預算。
在本研究中，成功地推導出以Jacobian比值做爲網格扭曲的計算指數，並應用於網格重建判斷法則中。在適應性分析方面，根據金屬成形大變形的特性，以節點上的應變差值，做爲新網格密度分佈的判準。至於網格重建後所產生節點穿透模具的問題，克服了以往必需將材料切除的瓶頸，而採用不損失材料質量的方法將穿透之節點壓因模具內。
本研究所發展的軟體系統的架構方式，是結合有限元素軟體(ABAQUS)與網格產生器軟體（可以是I-DEAS、PATRAN或ABAQUS-PRE），在網路的環境下，可以同時有多個使用者充分使用所有資源，進行多個分析工作。因此，對於各應用軟體間的溝通與支援等問題，在本研究中已完全克服，並將整個綱格重建過程完全自動化。

關鍵字

金屬成形模擬 ； 網格再切割 ； 網格重建自動化 ； 有限元素法 ； 適應性分析 ； ABAQUS商用軟體

並列摘要

When finite element methods are used to simulate metal forming problems, the commonly employed approach is Lagragian description. The major difficulty of the method is the severe distortion of the mesh during the simulation, which can strongly affect the accuracy of the solutions. Therefore, it is necessary to remesh at some appropriate points so that the analysis can continue with better-shaped meshes. Since the task of constructing a new mesh is time-consuming and error-prone, also much analysis time is often wasted if element distortion is only inspected by the users sporadically, automating the entire remeshing process is extremely worthwhile.
In this paper, we first examine the geometric meaning of Jacobian. By using the Jacobian ratio as the distortion index, we have successfully established a remeshing criterion. In creating a new mesh, the idea of adaptive ana1ysis, based on the strain jumps at nodes which reliably reflect the characteristics of large deformation of metal forming, is adopted to determine proper element distributions. As for the problem of nodes penetrating the die after remeshing, we propose a new method for pushing the outside nodes back to the die surface. The method, as opposed to the previous methods of removing the materials, have shown to effectively resolve the long-standing penetration problem through analyses of many difficult problems. A software system is developed which includes the above-mentioned criteria and the necessary ingredients to accomplish the automatic remeshing procedures. The system adopts the widely-used commercial finite element program ABAQUS as the analysis engine and I-DEAS as the mesh generator. The design of the software system is aimed at freely using all of the ana1ysis and meshing programs available in the network. The relevant communication problems among the softwares and the computer systems have all been overcomed in this work.

並列關鍵字

V-gutter ； span angle ； centerbody