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博碩士論文 etd-0903103-132413 詳細資訊
Title page for etd-0903103-132413
論文名稱
Title
擠製製程時中央破裂缺陷形成之研究
Study on formation of central bursting defects in extrusion processes
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
84
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2003-07-30
繳交日期
Date of Submission
2003-09-03
關鍵字
Keywords
中央破裂缺陷、擠製、延性破壞準則、臨界破壞值
ductile fracture criterion, extrusion, critical damage value, central bursting defects
統計
Statistics
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The thesis/dissertation has been browsed 5628 times, has been downloaded 32 times.
中文摘要
本論文主要是提供一套預測材料缺陷形成之方法。以擠製製程為例,藉由有限元素軟體DEFORMTM-2D模擬分析,研究鋁材AA6061於擠製加工後,可能形成中央破裂缺陷之時機;探討在不同加工條件下,半模角、斷面縮減率、模具與胚料間之摩擦因子及材料應變硬化指數等,對擠製成品最大破壞值之影響,並且比較不同延性破壞準則模擬擠製結果之差異性,且找出材料本身之臨界破壞值。另外再以材料機械性質試驗,如均勻試片與缺口試片拉伸試驗、壓縮試驗和環壓試驗等,獲得模擬所需之強度係數K值、應變硬化指數n值、CDV值及摩擦因子m值。
最後進行冷間多道次擠製實驗,來驗證有限元素模擬的適用性及準確性。本文已完成連續三道次擠製實驗,但未見破壞產生,其原因為第三道次之最大破壞值1.0479未超過臨界破壞值1.068,,所以實驗結果不會有中央破裂缺陷形成。

Abstract
This paper describes a method by means of FE code DEFORMTM-2D to simulate the formation of central bursting defects in extrusion processes; the effect of various extrusion parameters such as half die angle, reduction in area, friction factor, and strain hardening exponent on the maximum damage value is examined. The differences between various ductile fracture criteria are compared and critical damage value(CDV) of the material AA6061 is found. In addition, we get the strength coefficient(K), strain hardening exponent(n), CDV and friction factor(m) by material tests, such as uniform tensile test, notched tensile test, compression test, and ring compression test.
Finally, the cold multistage extrusion experiment was conducted to verify the accuracy of the finite element simulations. From the continuous three pass extrusion experimental data, no fracture in the center of the extruded product was found. From the analytical data, it was known that the maximum damage value 1.0479 for third pass extrusion was small than critical damage value 1.068, thus, central bursting defects didn’t occur in extrusion processes.

目次 Table of Contents
目錄
中文摘要…………………………………………………..…Ⅰ
英文摘要………………………………………………………..…Ⅱ
目錄……………………………………………………………..…Ⅲ
表目錄…………………………………………………………..…Ⅵ
圖目錄…………………………………………………………..…Ⅶ
符號說明………………………………………………………..…Ⅹ
第一章 緒論…………………………………………………..……1
1-1 前言…………………………………………………………………1
1-2 擠製加工之分類與特色……………………………………………2
1-3 文獻回顧……………………………………………………………4 
1-3-1理論解析方面……………………………………….………4
1-3-2實驗方面…………………………………………….………4
1-3-3有限元素模擬方面………………………………….………5
1-4 本論文之研究目的…………………………………………………7
1-5 本論文之基本架構…………………………………………………8
第二章 有限元素軟體之介紹與延性破壞………………………...…9
2-1 有限元素軟體DEFORMTM-2D之介紹……………………………9
2-1-1基本架構與主要模組功能………..…………………………9
2-2 延性破壞………………………………………………………..…11
2-2-1延性破壞準則之分類………………………………………13
2-2-2材料臨界破壞值的求得方法………………………………15
2-2-3本實驗用鋁材(AA6061)之臨界破壞值……………………16
第三章 中央破裂缺陷之解析與模擬…………………………...20
3-1 中央破裂缺陷之形成機制………………………..………………20
3-2 冷間擠製製程之模擬參數設計………………..…………………22
3-3 單道次一階段擠製模擬……………………..……………………25
3-3-1軸向應力和破壞值、等效應力、等效應變之分佈……….…26
3-3-2不同加工條件對最大破壞值之影響…………………….…27
3-3-3鋁材AA6061擠製時之臨界曲線……………………..……31
3-4 單道次二階段擠製模擬……………………………………..……33
3-4-1軸向應力和破壞值、等效應力、等效應變之分佈……….…33
3-4-2半模角對最大破壞值之影響(固定出、入口直徑)…………35
3-4-3中心軸上無因次應力值之分佈…………….………………35
3-5 多道次二階段擠製模擬…………………………………………36
3-5-1比較各道次間破壞值分佈之情形…………………………36
3-5-2中央破裂缺陷之形成………………………………………38
3-5-3不同延性判斷準則之模擬結果……………………………39
第四章 冷間擠製實驗…………………………………………………41
4-1 材料性質試驗……………………………………………………41
4-1-1均勻試片之拉伸試驗………………………………………41
4-1-2缺口試片之拉伸試驗……………………………………45
4-1-3壓縮試驗……………………………………………………46
4-1-4圓環壓縮試驗………………………………………………51
4-2 多道次冷間擠製實驗……………………………………………54
4-2-1多道次擠製實驗設備與模具之製作………………………54
4-2-2冷間擠製實驗步驟…………………………………………59
4-2-3解決胚料彎曲之方法………………………………………60
4-3 擠製實驗結果與討論……………………………………………61
4-3-1第一道次擠製………………………………………………61
4-3-2第二道次擠製………………………………………………62
4-3-3第三道次擠製………………………………………………62
4-3-4多道次冷間擠製實驗與模擬結果之比較…………………63
第五章 結論………………………………………………………………68
5-1 研究成果之概要…………………………………………………68
5-2 未來研究之課題…………………………………………………69
參考文獻…………………………………………………………………70
參考文獻 References
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