臺灣博碩士論文加值系統

在塑性加工之研究當中有限元素法的運用已經行之有年了，而端鍛製程更是普遍且重要的金屬加工方式。另外顯性動態有限元素理論(dynamic-explicit FEM)開始有學者用來模擬各種金屬成型問題，其優點有節省記憶容量、提高計算效率，亦可輕易處理接觸狀況。所以本文利用動態有限元素分析軟體（LS-DYNA）來分析鋁合金（A6061-T6）方形柱的端鍛加工。探討在不同的速度及質量因子條件下的鍛造負荷、材料的變形、內部的應力及應變的分佈情形以及電腦計算時間的差異。
本文以端鍛製程之動態顯性有限元素模擬，探討動態分析軟體在不同的設定參數之下，如速度、質量密度、網格尺寸以及接觸間隙來觀察整個端鍛加工模擬過程之變化與影響。最後並透過實驗的驗證，來比較數值模擬分析與實驗數據之結果的差異性，希望經由本文的模擬分析，建立一個基本的、適用的模擬準則，做為分析軟體之入門訓練範例，並以此基準運用於其他的複雜成形加工問題，進而節省在模擬或製造上所做金錢及時間上的花費。
而將有限元素分析結果與壓縮實驗進行比對，發現實驗結果與有限元素分析結果趨勢相同，如模擬之工件模型外型的變形結果以及負載壓力等等，由此可證明利用動態有限元素分析軟體模擬端鍛製程具備一定的可行性。

In the past decade, the researches of metal forming focus on the upsetting process still a popular and common topic. Since the shape of billet is easy to model, and the control parameters are obtained quickly, make the numerical simulation of upsetting process as a useful case studying. The dynamic FEM code, LS-DYNA, is used in this study. Attention on applications of the velocity and mass factor techniques for the A6061-T6 aluminum square billet in the upsetting process are modeled. The predicted load, the material distortion, the stress distribution, and the computing time of computer are presented, the usage of these factors at proper time also discussed.
In the investigations of the upsetting process by the dynamic-explicit FEM analysis, detail discussions in the simulation with variations of relative parameters, such as velocity, mass density, and mesh size etc. are assessed. The fully history of deformation states and some defects in the simulations are observed, then, the modified and available model is suggested. Finally, it is through the verification of the experiment, the comparisons between the numerical simulation and the experiment show a reasonable tendency. Goal of this research, is hope to set up a basic simulation modeling for the numerical analysis, and then apply to the other complicated metal forming problems, the benefits of reducing the analysis cost, and saving the design time of manufacturing process are dramatic.

中文摘要......................i
英文摘要......................ii
誌 謝......................iii
目 錄......................iv
表 目 錄......................vii
圖 目 錄......................viii
符號說明......................xi
第一章 緒論....................1
1.1 前言......................1
1.2 研究動機與目的.............3
1.3 論文架構..................4
第二章 有限元素法理論...........5
2.1 有限元素法簡介.............5
2.2 統制方程式.................6
2.3 中央差分法.................9
第三章 有限元素分析軟體.........13
3.1 LS-DYNA簡介...............13
3.2 軟體程式架構...............13
3.2.1 前處理器.................15
3.2.2 主程式求解器..............15
3.2.3 後處理器..................16
3.3 接觸分析演算法...............16
3.3.1 動力約束法................17
3.3.2 分配參數法................17
3.3.3 罰函數法..................18
第四章 模擬分析流程及模型.........21
4.1 分析流程....................21
4.2 幾何模型....................22
4.3 材料定義....................24
4.4 網格元素屬性選擇.............26
4.4.1 薄殼元素..................27
4.4.2 實體元素..................28
4.5 接觸模式定義.................30
4.6 邊界條件設定.................34
4.7 控制因子....................36
4.7.1 速度因子..................36
4.7.2 質量因子..................36
4.8 初始穿透....................38
第五章 結果與討論................39
5.1速度、質量之控制因子...........40
5.1.1 速度因子..................40
5.1.2 質量因子..................44
5.1.3 速度及質量因子.............51
5.2 模型間之適當間隙及薄殼厚度.....55
5.2.1 模型間隙...................56
5.2.2 薄殼厚度..................58
5.3 實驗與模擬之結果比較..........60
5.3.1 壓縮試驗機及實驗流程........60
5.3.2 端鍛負荷...................62
5.3.3 材料變形...................63
5.3.4 內部應力及應變..............66
第六章 結論及未來展望..............69
6.1 結論.........................69
6.2 未來展望.....................70
參考文獻.........................71
簡 歷.........................74

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