A New Methodology for Analyzing Powder Energy Absorptivity on Direct Energy Deposition (DED) System

Abstract

　　Additive Manufacturing such as Directed Energy Deposition (DED) process has strong potential in manufacturing parts DED uses thermal energy of laser beam to fuse the metal substrate for creating the molten pool on the surface of the substrate and then Multiple streams of metal powders are simultaneously injected into the molten pool for material deposition The procedure described above is repeated line by line layer by layer to manufacture complex 3D parts Physical phenomenon associated with DED process is highly complex including absorption and scattering of laser radiation with powder particles in the concentration region and substrate thermal conduction the formation and solidification of the melt pool and so on 　　The present study proposes a new methodology to construct the volumetric heat source for heat transfer simulation of DED process For modeling the volumetric heat source computational fluid dynamics (CFD) simulation is first performed to estimate dimensions and location of the powder concentration region Additionally the powder mass distribution in the concentration region is also attained Subsequently Monte Carlo ray tracing simulation is performed to calculate the total powder energy absorptivity of the concentration region It is shown that the simulated results of the average powder concentration region and total absorptivity are in good agreement with the experimental results Finally the effects to the average absorptivity of the metal powder and substrate regarding to the powder mass flow rate and powder-gas flow rate are discussed To the best of our knowledge this is the first finding in the total laser absorptivity of the concentration zone in DED process without any fitting estimation

Date of Award	2018 Aug 16
Original language	English
Supervisor	Yu-Lung Lo (Supervisor)