本研究目的為使用一含有Knudsen Layer 蒸發模型與表面追蹤方程式之三維數值模型用以模擬平板雷射銲接燒熔過程，模型中以多相流流體體積法(VOF)計算空氣相及金屬相，動量方程式考慮固液化源項、馬倫格尼力(Marangoni force)、表面張力(Surface tension)及反衝壓力(Recoil force)，能量方程式考慮雷射熱及蒸發熱，為觀察金屬元素在燒熔過程中的變化，在模型中加入物種方程式並考慮蒸發源項。當中關於反衝壓力、蒸發熱及金屬元素蒸發通量由Knudsen Layer 蒸發模型之觀點求得。過往研究雷射銲接之數值模擬中關於反衝壓力、蒸發熱(Evaporation heat)，因考量金屬蒸發後部分金屬蒸氣凝結，固在兩源項各乘上一固定係數，此兩係數的應用是以模擬結果符合實驗為準，並無使用規律，但在Knudsen Layer 蒸發模型之觀點下，此係數應隨著熔池內溫度變化到達一定程度後才為定值。所使用之材料為鋁合金(Al-5182)，僅關注質量分率高於1%之鋁及鎂。
將本研究之模擬結果與文獻實驗數據進行相比，熔池尺寸大致吻合。藉由進行對比本研究數值模型與文獻中數值模型，分析本研究因考慮多種源項使得模擬結果較符合物理現象，且因額外計算物種方程式，可透過數值模型觀察雷射燒熔過程中，熔池內鎂元素的變化，從中可知熔池內鎂元素蒸發形成含量梯度後，由馬倫格尼力及對流效應的影響，使其在熔池內混合均勻。後將不同雷射加工參數之案例，以無因次焓之順序進行排列並觀察其趨勢，發現本研究的模擬結果大致符合無因次焓越大，鎂損失量越大的趨勢。最後將不符合趨勢之案例進行改進，將部分金屬性質改為隨溫度變化後，發現熔池尺寸誤差縮小，更貼合實驗數據。

This study employs a three-dimensional numerical model, combining the Knudsen Layer evaporation model and a surface tracking equation, to simulate the laser welding process of flat plates. The model uses the Volume of Fluid (VOF) method to calculate the air and metal phases, and considers the source terms for solid-liquid phase change, Marangoni forces, surface tension, recoil pressure, laser heat, and evaporation heat. Additionally, to observe the changes in metal elements of Al-5182 during the welding process, a species equation is used, focusing on aluminum and magnesium with mass fractions greater than 1%.
The recoil pressure and evaporation source terms are obtained through the Knudsen Layer evaporation model. Unlike previous studies that applied fixed coefficients, this model adjusts these coefficients based on temperature.
Comparison with experimental data shows that the simulated molten pool size generally aligns with the literature results. By incorporating multiple source terms and calculating the species equation, this model better replicates physical phenomena, particularly the uniform mixing of magnesium in the molten pool caused by Marangoni forces and convection effects. An analysis of dimensionless enthalpy reveals that higher enthalpy values correspond to greater magnesium loss. By adjusting the metal properties in non-conforming cases to account for temperature variation, the results more closely follow the observed trend.

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