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博碩士論文 etd-0024117-143656 詳細資訊
Title page for etd-0024117-143656
論文名稱
Title
以數值方式研究選擇性雷射燒熔過程
A Numerical Investigation of Selective Laser 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
46
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
2017-01-17
繳交日期
Date of Submission
2017-01-24
關鍵字
Keywords
馬倫格尼效應、蒸發熱、反衝壓、高斯雷射、選擇性雷射燒熔
Gaussian laser, Selective Laser Melting, Marangoni force, Heat of vaporization, Recoil pressure
統計
Statistics
本論文已被瀏覽 5688 次,被下載 351
The thesis/dissertation has been browsed 5688 times, has been downloaded 351 times.
中文摘要
本文主要目的為以計算流體力學為基礎建立一選擇性雷射燒熔(Selective Laser Melting)數值模型,藉以模擬一在空間及時間上皆以高斯形式分佈之雷射作用於金屬粉末上其相變化之過程,觀察燒熔過程中液態金屬之暫態流動行為及其物理特性之變化。本研究將模擬過程分為熔融及固化兩部份,熔融過程包含金屬受熱熔化後因重力影響而向下垂流及液體金屬接觸到周圍未熔融金屬後接續之一般熱傳行為。當雷射遠離作用區後,液態金屬不再接受外部熱源開始散熱,熔池溫度逐漸下降進入固化過程,直至熔池溫度均降至熔點以下始結束一完整燒熔流程。此外,透過本研究之模擬結果也可得知結構體是否有孔隙或其他缺陷產生。

本研究考慮了反衝壓(Recoil pressure)、表面張力(Surface tension force)、蒸發熱(Heat of Vaporization)、馬倫格尼效應(Marangoni effect),使數值模型能與實際物理現象更為吻合。本研究可觀察燒熔過程中微觀的物理現象,並可針對不同雷射參數、粉末尺寸進行模擬,將其對應之結果製作出參數矩陣,此矩陣可在實際燒熔前預判結構體之最後成形輪廓。
Abstract
The main purpose in this research is to develop a Selective-Laser Melting (SLM) numerical model, to simulate a Gaussian laser acting right on metal powder, and observe the phase change of the metal, formation of cracks in the metal during the melting process based on Computational Fluid Dynamic. Different melting processes can be carried out from numerical experiment, such as laser power, laser scanning speed, and metal powder size. The model in this research includes Volume of Fluid method to define powder surface, employed Delta function to capture it and forced laser acts right on the interface. Furthermore, this study considers recoil pressure, surface tension, heat of vaporization.
目次 Table of Contents
目錄
致謝 i
中文摘要 ii
Abstract iii
目錄 iv
圖目錄 vi
表目錄 vii
符號說明 viii
第一章 緒論 1
1.1 積層製造背景、與傳統製造工法之比較 1
1.2 選擇性雷射燒熔簡介 4
1.3 研究目的 5
1.4 文獻回顧 5
1.4.1 積層製造常見之缺陷成因 5
1.4.2 積層製造模擬 7
第二章 研究方法 12
2.1 數值模型 12
2.1.1 連續方程式 14
2.1.2 動量方程式 15
2.1.3 能量方程式 16
2.2 多相流模型 18
2.3 固化/液化模型 18

2.4 數值模型幾何、網格、流場邊界條件、雷射熱源及流場初始化設定 20
第三章 研究成果分析 22
3.1 選擇性雷射燒熔之暫態過程分析 22
3.2 模擬與實驗結果比較與討論 25
3.3 針對1250 mm/s算例之源項分析 26
3.3.1 加入源項K之比較 26
3.3.2 自由表面流討論 27
3.3.3 熔池內流體速度及流動方向 29
3.4 研究上遭遇之困難 30
第四章 結論與建議 31
參考文獻 32
參考文獻 References
參考文獻

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