本研究主要分為兩個部份，第一部分針對積層製造中的離軸式送線型直接能量沉積建立三維數值模型，利用套裝軟體ANSYS Fluent 18.0進行數值計算，配合多相流模型(Volume of Fluid, VOF)將計算域分為氣體相(Argon)與金屬相(S45C)，並且於動量方程式中考慮固液化模型(Solidification Model)、表面張力(Surface Tension)、反衝壓力(Recoil force)、馬倫格尼效應(Marangoni effect)以及含有硫(Sulfur)之金屬在流動上的影響，在能量方程式中加入高斯分布之雷射熱源，模擬線材與基板受雷射加熱至熔化，隨著機台移動在基板上形成一道融覆層。將此模型設定針對9組實驗加工參數設置進行模擬比對融覆層尺寸後，進一步以流場角度分析不同加工參數下，對於融覆層寬高深的影響，以及有無硫成分之流動變化對融覆層的影響。第二部分利用先前建立完成的同軸式送粉型直接能量沉積三維模型，將數值模擬在有無考慮基板效應所得到的粉末濃度，以源項形式加入連續方程式，分析兩者對於融覆層尺寸的影響。

由第一部分模擬結果分析得到，送線型直接能量沉積的融覆層寬高深成形速度，由深度最快定型高度最慢定型，深度主要受到雷射能量引起的反衝壓力影響，寬度受到前期馬倫格尼力以及雷射光斑的影響，高度需等待雷射遠離後由馬倫格尼力決定，並受到較早成形的寬度影響，其中含硫的金屬有使寬度縮減高度上升的趨勢，並且能縮短融覆層到達穩定的時間。由第二部分模擬結果得到，送粉型直接能量沉積在顆粒較大的的情況下，有無基板的粉末濃度分布差異不大，因此能直接採用解析模型得到的濃度分布做計算，以節省計算時間。

This study comprises two main parts. In the first part, a numerical model for the off-axial wire feeding direct energy deposition process in additive manufacturing is developed using the Volume of Fluid (VOF) approach in ANSYS FLUENT 18.0. The model considers various physical mechanisms, including solidification, surface tension, recoil force, Marangoni effects, and the presence of sulfur in the metal, accounted for through source terms in the momentum equation. A Gaussian distribution laser heat source is incorporated into the energy equation to simulate the laser heating process, resulting in the formation of deposited layers on the substrate. Validation of the model is achieved through comparisons of cladding geometry measurements with experimental data for different process parameters. Subsequently, the model is utilized to analyze the effect of flow fields on cladding geometry and investigate differences between metals containing sulfur and those without sulfur.

The second part of the study employs the three-dimensional model of coaxial powder-fed direct energy deposition. Numerical simulations of powder concentration are conducted by introducing powder distribution as a source term in the continuity equation, with and without considering the substrate effect. The objective is to analyze how these scenarios influence the dimensions of the deposited layers.

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