雷射沉積過程中粉末噴流之高解析度數值模擬

High-fidelity numerical simulation of coaxial powder flow for the laser direct deposition process

麥育軒(Yu-Hsuan Mai)

指導教授 ： 周逸儒

國立臺灣大學/工學院/應用力學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103453

摘要

雷射金屬基層製造(LMD-AM)被歸類為基層製造(AM)類型中直接能量沉積製造(DED)之下的一個類別，在工業界中，粉末噴流的射出條件有許多種，使用多個同軸噴嘴噴出粉末，亦或是單個噴嘴，不同的發散角、雷射、顆粒性質與基層的掃描速度都會大大地影響了積層製造的品質，本研究使用大渦流模擬(Large eddy simulation)模擬環型結構下雷射積層製造中的粉末噴流，使用A.J. Chorin(1967)映射法(fractional method)分成預測步(predictor)與修正步(corrector)，並配合壓力的波松方程式(Poisson equation)去求解統御方程式，以(Chou et al ,2015)尤拉-拉格朗日數值模型來模擬顆粒運動過程，配合顆粒移動演算法儲存顆粒資訊，分析流況下顆粒在不同截面下的分布，同時也對比無流場的顆粒分布，觀察顆粒受流體之影響，另一方面，將高斯分布應用在雷射與顆粒位置上，在顆粒的能量方程式上，考慮其與雷射、潛熱、周圍氣體的熱交換模式，此外，進行了五種不同情況的模擬設置，除了與Wen et al(2009)所做之實驗數據進行比較，也有為實際在雷射基層製造中常見的大小設置，並觀察在有無流體的情況顆粒分布的差別下以及基板高度的不同對對流體紊流動能、紊流耗散、平均流場以及顆粒分布的影響。

關鍵字

大渦流模擬 ； 雷射基層製造 ； 同軸粉末噴流

並列摘要

The laser metal deposition additive manufacturing process(LMD-AM) is one of the seven classes of AM that falls under the ‘Directed Energy Deposition’(DED). In the industry, there are many kinds of injection conditions for coaxial powder flow, using single or multiple coaxial nozzles with different divergence angle, laser beam intensity, powder properties, scanning speed will greatly affect the quality of the laser metal deposition. In this study, we apply the large eddy simulation(LES) to simulate the annular coaxial powder flow for the laser deposition process. The model is a three-dimensional incompressible flow simulator, which is capable of resolving the government equation with fractional method. Apply the Euler-Lagrange model to simulate the particle with particle-moving algorithm that exchanges particle between Eulerian meshes is developed that automatically retains the necessary particle information. Also, compare the particle properties and distribution in different circumstances. The model is then validated against the experiment results. The flow field, laser attenuation, particle properties are all discussed in the simulation.

並列關鍵字

large eddy simulation ； laser deposition ； coaxial powder flow

參考文獻

[1] Lin J (1999) Concentration mode of the powder stream in coaxial laser cladding. Opt Laser Technol 31:251–257

[2] L. Wiegler, Jumping off the page, Eng. Technol 3(1) (2008) 24–26.

[3] A. J. Pinkerton, An analytical model of beam attenuation and powder heating during coaxial laser direct metal deposition, J. Phys. D: Appl. Phys 40 (2007) 7323–7334.

[4] J. M. Jouvrd, D. F. Grevey, F. Lemoine, A. B. Vannes, Continuous wave nd:yag laser cladding modeling: A physical study of track creation during low power processing, J. Laser Appl 9 (1997) 43–50.

[5] Z. Liu, H.-C. Zhang, S. Peng, H. Kim, D. Dua, W. Conga, Analytical modeling and experimental validation of powder stream distribution during direct energy deposition, Additive Manufacturing 30 (2019) 100848.