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博碩士論文 etd-0805109-160958 詳細資訊
Title page for etd-0805109-160958
論文名稱
Title
尺寸分析熔化過程中之熱毛細對流力 造成之熔區形狀研究
Scaling molten pool shape induced by thermocapillary force in melting
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
63
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
2009-06-30
繳交日期
Date of Submission
2009-08-05
關鍵字
Keywords
表面張力梯度、焊接、熔化、尺寸因次分析、馬里哥尼對流、熱毛細對流
thermocapillary convection, scale analysis, Marangoni convection, surface tension gradient, melting, welding
統計
Statistics
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中文摘要
本研究是利用尺寸因次分析,熔池形狀和馬里哥尼流(熱毛細對流)對表面張力係數為負且Prandtl number大於1時,焊接或熔化過程中所帶來的影響。
當Prandtl number大於1時,意味著熱邊界層小於速度邊界層,表面張力係數為負時,表面的流動是由內往外流動的。計算熔化的熔池形狀和熔化區的強度、微結構、機械性質與熔化區域的特性是密切相關的。
因為Marangoni number和Reynold number可能大於一萬,傳輸過程可以用尺寸因次分析來確定。在這裡,熔池在平整的表面上被分成熱、中間和冷角落地區,分析熔化前在固體液體界面的邊界層,結果發現熔池形狀、表面速度和溫度的分佈可以用 Marangoni number、Prandtl number、Peclet number和入射能量表示出一致的方程式。經由尺寸因次分析預測的結果可與數值計算以及實驗數據相符合。
Abstract
The molten pool shape and thermocapillary convection in melting or welding of metals or alloys having negative surface tension coefficients and Prandtl number greater than unity are determined from a scale analysis.
Negative surface tension coefficient indicates that the surface flow is in outward direction, while Prandtl number greater than unity represents that boundary layer thickness of conduction is less than that of momentum. Determination of the molten pool shape is crucial due to its close relationship with the strength, microstructure and properties of the fusion zone.
Since Marangoni and Reynolds number are usually greater than ten thousands, transport processes can be determined by scale analysis. In this work, the molten pool is divided into the hot, intermediate and cold corner regions on the flat free surface, boundary layers on the solid-liquid interface and ahead of the melting front for analysis. The results find that the pool shape, surface speed and temperature profiles can be self-consistently evaluated as functions of Marangoni, Prandtl, Peclet, Stefan, and beam power numbers. The predictions agree with numerical computations and experimental data in the literature.
目次 Table of Contents
謝誌 I
目錄 II
圖目錄 IV
符號說明 VI
中文摘要 XI
英文摘要 XII
第一章 序論 1
1.1前言 1
1.2研究目的 5
1.3本文架構 6
第二章 系統模型之假設與理論分析 7
2.1系統模型與假設 7
2.2理論分析 9
2.3無因次收斂分析 13
第三章 結果與討論 14
3.1尺寸因次分析 14
3.2模擬結果與討論 20
第四章結論 46
參考文獻 47
參考文獻 References
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