以計算流體力學分析直接式能量沉積及粉床燒熔之積層製程

The Laser Additive Manufacturing (AM) has been developed and gained a lot of attention nowadays. It displays advantages especially for customized products with complex structures. This project will utilize the computational fluid dynamics (CFD) technique with the basis of the volume of fraction (VOF) method to simulate the selective laser manufacturing (SLM) process, including the direction energy deposition (DED) and powder bed fusion (PBF). The approach of VOF can capture and update the interface between the melting powder and ambient gas such that the laser energy can be guaranteed to work properly. The physical process consists of multiple phenomena, including the melting and the ensuing evaporation of the metal powder during the rise of temperature by laser power, and the solidification of the melting pool as the temperature drops. Besides, the surface tension, Marangoni effect, and the evaporative recoil pressure onto the free surface of the melting pool can significantly affect the profile and strength of the products. These interfacial forces have been taken into account to study the ensuing heat transfers and the influence on the morphology of the melt pool. After the establishment and validation of the numerical models, the numerical analysis through the micro- and macroscale viewpoints can help the understanding of the laser manufacturing process. With the aid of the parameter matrix from the CFD results, the numerical predicts could provide the first-hand optimal design parameters before the experiments have been carried out. It can reduce the manufacturing cost, improve the quality of the product, and avoid the defects in the future.