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研究生:陳佳陽
研究生(外文):Chia-Yang Chen
論文名稱:反向多道次單點增量成形之研究
論文名稱(外文):Reverse Multi-Step Single Point Incremental Forming
指導教授:李貫銘李貫銘引用關係
指導教授(外文):Kuan-Ming Li
口試委員:楊宏智陳復國黃庭彬
口試委員(外文):Hong-Tsu YoungFuh-Kuo ChenTyng-Bin Huang
口試日期:2019-07-04
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:機械工程學研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2019
畢業學年度:107
語文別:中文
論文頁數:111
中文關鍵詞:單點增量成形CAE成形角度極限板材厚度提升反向多道次成形
DOI:10.6342/NTU201901357
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少量多樣的客製化生產模式是目前製造業的趨勢,與板金沖壓相比,增量成形不受模具造型的限制,也不需要龐大的設備,因此在少量生產的條件下,其製造成本遠低於沖壓成形。在造型方面,增量成形的變化度相當高,使用者僅需將成品造型透過適當的路徑規劃軟體生成加工路徑,即可進行製造。增量成形之加工技術,目前在客製化的醫療用品及汽車工業的原型打樣等領域皆有相當發展。
單點增量成形中,不同的成形角度、板材厚度、工具尺寸及進給深度都會對成品結果造成影響;不同的材料也會因為其機械性質,而有成形角度之限制,過大的成形角度將導致應變超過材料之成形極限,最終使成品破裂。為改善單點增量成形之缺陷,目前研究主要都改以多步驟單點增量成形,每道次加工皆以相同方向對目標造型進行成形,雖有助於提升板材之成形性,但也導致板材在厚度上分佈不均、造型的深度極限降低及多步驟成形產生之剛體移動,使板材因多次加工的造型累積產生階梯狀的殘料,造成造型的精確度有待改善。
本研究的板材材料為AA1050-O,並將欲成形之軸對稱圓錐CAD檔案匯入MATLAB所撰寫的程式進行路徑規劃,並以有限元素軟體Abaqus進行模擬分析。藉由板金沖壓的反向再引伸為概念結合單點增量成形,本研究提出反向式單點增量成形之加工策略,透過適當的反向預成形輔助,將目標造型之板材厚度及分佈做適當的改善,在45度之軸對稱圓錐,板材最低厚度提升7%;而在60度之軸對稱圓錐,板材最低厚度提升17%。為使單點增量成形適用於各種造型,本研究以反向垂直成形的加工策略,將成形角度由原先單步驟成形之72度極限提升至90度,並改善多步驟成形之造型殘料。利用多道次的反覆加工,對每一道次成形之距離及角度做出適當的配置,最終在不超出成形極限下完成垂直造型加工,提升單點增量成形之可成形角度及成形性。
A small number of customized production models are the current trend in manufacturing. Compared with traditional stamping, incremental forming is not limited by mold and does not require huge equipment. Therefore, under a small amount of production, the cost of incremental forming is lower than stamping process. On the other hand, changing the shape of model is easier in incremental forming, user only needs to modify the CAD and import into software to generate the toolpath, and then let the machine to work. Nowadays, the technology of incremental forming has been quite developed in the fields of customized medical products and prototype of the automobile industry.
In single point incremental forming (SPIF), different forming angle, thickness, tool size and feed depth all have an effect on the product. Different materials are also limited in forming angle due to their mechanical properties. If working beyond the limited angle, it will cause the strain to exceed the forming limit curve (FLC) of material and eventually break the product. In order to improve the defects of SPIF, most of forming strategies are changed to multi-step incremental forming instead of single step incremental forming. In multi-step incremental forming, each step forms the target shape in the same direction, which improves the formability of the metal sheet, but also causes uneven distribution of the sheet thickness and the rigid body motion. Rigid body motion causes the stepped features on the shape, and it makes the poor precision of the shape.
In this research, material AA1050-O was selected, and the CAD of axisymmetric cone was imported into the program written by MATLAB to generate the toolpath, and then analyzed by the finite element software Abaqus. The strategy of reverse single point incremental forming combines the concepts of reverse redrawing of sheet metal and single point incremental forming. With appropriate reverse pre-forming in this process strategy, the distribution and thickness of the metal sheet can be well improved. With proper reverse single point incremental forming, the minimum thickness of the sheet is increased by 7% at an axisymmetric cone of 45 degrees, and the minimum thickness of the sheet is increased by 17% at an axisymmetric cone of 60 degrees.
In order to make single-point incremental forming suitable for various shapes, this research used a reverse vertical forming process strategy to increase the forming angle from the 72 degrees limit of the original single-step forming to 90 degrees, and to improve the precision of the shape. By multi-step of reverse vertical forming process, the distance and angle of each step are appropriately configured. Finally, the reverse vertical process completes the target shape without exceeding the forming limit, and the formable angle and formability of SPIF are improved.
口試委員會審定書 i
誌謝 ii
摘要 iii
Abstract iv
目錄 vi
圖目錄 ix
表目錄 xiv
第一章 緒論 1
1.1 前言與研究背景 1
1.2 研究動機與目的 5
1.3 文獻回顧 7
1.4 研究方法與步驟 11
1.5 論文總覽 14
第二章 單點增量成形之機制探討 15
2.1 正弦法則(Sine law) 15
2.2 板材之應力與應變 16
2.3 最大成形角度限制 19
2.4 加工參數之影響 20
2.5 加工路徑 23
2.6 成形極限 24
2.7 多步驟單點增量成形 27
第三章 單點增量成形模型建立 31
3.1 實驗目的 31
3.2 實驗設備 31
3.2.1 成形設備 31
3.2.2 成形材料 33
3.2.3 成形工具 34
3.2.4 成形夾具 36
3.3 實驗方法 38
3.4 有限元素分析軟體 43
3.5 材料試驗 45
3.5.1 拉伸試驗 45
3.5.2 成形極限 48
3.6 數值模型建立 49
3.7 加工路徑生成 51
3.8 收斂性測試 55
3.8.1 負載速率 56
3.8.2 質量縮放 57
3.8.3 網格大小 58
3.8.4 元素積分點 60
3.8.5 收斂性測試結果 61
3.9 數值模型驗證 62
第四章 反向多道次成形之探討與改善 65
4.1 單步驟單點增量成形之模擬分析 65
4.2 反向式單點增量成形之目的與方法 67
4.3 預成形造型參數探討 69
4.3.1 預成形角度 70
4.3.2 預成形位置 74
4.3.3 預成形長度 77
4.3.4 預成形之參數探討 80
4.4 反向式單點增量成形之規劃與結果 83
4.5 反向垂直成形之目的與方法 87
4.6 反向垂直成形之應變探討 90
4.7 成形工具之尺寸探討 92
4.8 多道次加工 94
4.9 反向垂直成形策略規劃與結果 97
第五章 結論與未來展望 105
5.1 結論 105
5.2 未來展望 107
參考文獻 108
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