臺灣博碩士論文加值系統

本文乃利用有限元素法進行表面張力流對雷射鍍層影響之數值模擬分析。在雷射鍍層過程中，融化金屬液體之表面張力係數會導致金屬鍍層厚度之變化並影響鍍層稀釋度，進而直接影響到工件加工後的機械性質。藉由有限元軟體FIDAP進行模擬計算並考量雷射能量、加工速度、表面張力係數以探討溫度場、融池流場及鍍層厚度之變化情形，用以分析表面張力流對雷射鍍層之影響。結果顯示：融熔金屬液體表面張力係數之變化會影響鍍層融池內部流場方向，進而牽引融池表面並造成鍍層外形厚度改變並且影響溫度分佈。於正的表面張力係數時，會降低鍍層厚度，同時並使得鍍層稀釋度增加。相反的，於負的表面張力係數時，會增加鍍層厚度，同時並使得鍍層稀釋度減少，這都會直接影響到加工件之品質。因此，表面張力係數對於鍍層工件之品質影響匪淺，實為加工製程中不可忽視之重要因素。

The purpose of this thesis is to simulate the effects of marangony flow on the laser cladding processing using finite element method based on three-dimensional model. In the laser cladding processing, the surface tension coefficient of melting metal could influence the thickness and dilution of the metal clad which is leading to the variation of the mechanical properties. Based on the FIDAP software package and processing parameters, the temperature field, flow field of melting metal and thickness of metal clad were investigated to analyze the effects of the marangony flow on the laser cladding processing. The results show that the positive surface tension coefficient will decrease the clad thickness and increase the dilution. On the contrary, the negative surface tension coefficient will lead to a thinner clad and a lower dilution. The process quality will be stronger influenced. Hence, the present results can provide an important data to industry demands and improve the quality of the laser cladding processing.

中文摘要..........................................Ⅰ
英文摘要..........................................Ⅱ
致謝.............................................Ⅲ
目錄.............................................Ⅳ
圖目錄...........................................Ⅵ
符號說明.........................................Ⅷ
第一章 緒論.....................................1
1.1 前言.....................................1
1.2 文獻回顧..................................4
1.3 研究動機..................................9
第二章 理論分析與數值模式.........................12
2.1 理論基礎..........................12
2.2 表面張力效應.......................14
2.3 稀釋度............................16
2.4 數值模式..........................18
2.5 假設條件..........................22
2.6 計算模擬步驟.......................23
第三章 結果與討論................................26
3.1 二維之鍍層數值模擬結果..............26
　3.1.1 鍍層加工速度對雷射能量之影響.........26
3.1.2 表面張力效應對鍍層厚度及稀釋度之影響..30
3.2 三維之鍍層數值模擬結果..............33
3.2.1 正剖面與側剖面之鍍層稀釋度比較.......33
3.2.2 表面張力現象對於融池內部流場之影響....37
3.2.3 加工速度對於鍍層厚度之影響...........42
3.2.4 雷射能量對於鍍層厚度之影響...........44
第四章 結論......................................46
第五章　 未來展望...................................48
參考文獻...........................................49
作者簡介...........................................53

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