本研究將針對積層製造中的離軸式定向能量沉積製程建立數值模型，將計算域分為氣體相氬氣和金屬相英高鎳合金(Inconel 625)，利用套裝軟體ANSYS Fluent 18.0模擬金屬相受到高斯分布雷射加熱基板時，使其局部達到熔點使形成熔池，粉末掉入熔池中成型，配合床台移動逐漸燒熔成一道熔覆層，同時以動量及能量之耦合計算流場中空氣相和金屬相的溫度、速度、熔池這些暫態變化。

在模擬過程中配合使用者自定義函數(User-Defined Function，UDF)，在動量部分考慮了固液化模型(Solidfication Model)、含硫(Sulfur Content)金屬的流動影響、表面張力(Surface Tension)、馬倫格尼力(Marangoni Force)，使金屬熔體在運動過程及最終外觀更符合真實物理現象；而在能量方程式方面，而雷射將受到粉末濃度之遮蔽效應(Attenuation Effect)，使能量隨加工深度及方向改變。另一方面由於雷射照射於粉末，使粉末在運動過程溫度逐漸升高，因此也考慮粉末熱(Powder Heat)之熱焓交換於方程式中。本文也將離軸型態噴嘴的金屬粉末沉積函數透過座標轉換的方式得到新的沉積函數寫入UDF中，在等效二維模型中進行計算。模型之計算將會根據文獻[27]中之實驗進行設置，並將模擬結果與該實驗結果的寬高進行比對，後續進而在觀察參數改動如發散角、硫成分這些改變的測試。最後也嘗試在現有的等效二維模型上發展為完全三維模型之計算，在該形態下模擬熔覆層。這些資訊在加工前就可經由模擬得知，在實際運用上降低尋找參數的時程，和避免原料成本的浪費。

This study established a numerical model based on the off-axis directed energy deposition process of additive manufacturing. A software package is used to simulate the metal substrate heated by Gaussian laser beams. Melting point of the substrate is reached locally to form a weld pool, into which powder falls to form a cladding layer gradually in accordance with the movement of the table. The coupling between momentum and energy is used to compute the transient variations of temperature and velocity of gaseous and metallic phases in the flow field. The change of flow field caused by sulfur-containing alloy is observed. This phenomenon leads to difference trend of temperature gradient of surface tension. When its temperature gradient switches from negative to positive value, a change in Marangoni flow field from outward to inward flow occurs. As a result, the width of the cladding layer is narrower and the melting pool is deeper because of the trend of inward flow.

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