電子束熔融技術，是金屬積層製造成型技術的一種，而金屬積層製造目前所遇到的問題皆與溫度息息相關，因此探討金屬積層製造過程中相變化熱傳問題是本研究主要目的。本文採用鈦金屬作為本研究材料，並搭配有限元素法撰寫程式來分析電子束熔融製造之熱傳情況，並以等效比熱法來處理潛熱的效應，於處理潛熱部分加入鬆弛法及調整人工液固共存區的大小來協助收斂。本文研究方法分為兩部分，於測試部分為了確保所建立地數值模式的可行性，本文從一維熱傳問題、二維固定熱源、移動熱源到疊層一一探討，最後與模擬軟體COMSOL的結果做比對。確定建立的數值模型可行之後，再套入金屬中心提供的實際加工參數，模擬實際狀況的熱傳情形。由數值分析結果可發現，有無考慮潛熱的溫度分布有明顯的差異，因此不宜忽略潛熱的效應。電子束熱源瞬間功率極高可使鈦金屬迅速升溫熔化，熱源照射方向之溫度梯度大，故疊層厚度太厚使表層熱源無法讓上一層達熔點溫度，造成層與層無法有效熔接成型，易呈鬆散狀。經由實際條件測試發現經五次熱源加熱以及四次疊層，將每次加熱分別利用程式以及COMSOL所得到之溫度鋒值做比較，發現兩者最大誤差百分比為4.4%，最小誤差百分比為0.7%可知，兩者模擬結果相當一致！由這些結果可知經由數值模擬的探討，能預測加熱物件的暫態溫度場分布，希望有助於金屬積層製造之熱傳相關研究。

Electron beam melting (EBM) is one of the additive manufacturing processes. So far, most of the encountered problems of metal additive manufacturing are all related to the temperature field. Accordingly, the main purpose of this study is to analyze the heat transfer problem of phase change during the manufacturing process. The numerical method adopted in this study is finite element method. On the basis of the finite element method theory, the heat transfer problem of EBM process is analyzed by the self-writing programs in FORTRAN and simulated by the software, COMSOL, simultaneously. Next, the results calculated by the FORTRAN programs are compared to those simulated by COMSOL. In this thesis, the effective specific heat method is applied to deal with the effect of latent heat. Furthermore, the relaxation method and adjustable range of the artificial mushy zone is used to improve the convergence of temperature. The process of this study starts from the one-dimensional heat transfer problem, the two-dimensional one with fixed heat source or the mobile heat source to the layer-adding heat transfer problem. At last, the actual process parameters provided by the MIRDC are used to simulate the heat transfer problem of actual manufacturing process of EBM. The results reveal that whether consider the effect of latent heat or not makes significant difference to the temperature field; therefore the effect of latent heat should not be ignored. Besides, the thickness effect of the adding-layer should be considered. Because of the high temperature gradient in y-direction, too thick adding-layer easily causes the layers unable to fuse together effectively. Moreover, the minimum percent error between the FORTRAN programs and COMSOL is 0.7%, and the maximum percent error is 4.4%. This shows that the results analyzed by FORTRAN programs and simulated by COMSOL are consistent with each other and have the same trend. The results of this study are expected to be helpful to the additive manufacturing researchers.

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