Date of Completion
Dr. Jiong Tang, Dr. Brice Cassenti
Field of Study
Master of Science
Laser and electron beam powder bed melting additive technologies are being rapidly adapted by industry. These technologies rely on the ability to produce defect free parts through a delicate control of the process. However, this process has not been attempted or has failed for many common metallic materials such as Aluminum. The objective of this thesis was to understand the thermal transport phenomenon in electron and laser beam powder melting technology through simulation and experiments and determine the suitable range of parameters that can be used for common metallic materials. A finite element model was developed using ANSYS APDL to explore thermal transport and phase change behavior in metallic powder bed additive manufacturing processes. To explore a broad base of novel engineering materials, simulations were run in Ti6Al4V, Inconel 718, Stainless Steel 316L and Al7075 in both selective laser melting and electron beam melting scenarios. Comparison of the four materials in each process showed that it is very challenging to develop and maintain melt pools in aluminum while melt pools are broad and robust in Inconel and titanium, even when subjected to much lower energy densities. Titanium and Inconel were also shown to have larger melt pools and shallower thermal gradients.
Effective powder thermal conductivity was used to encapsulate all modes of heat transfer occurring at the inter-particle level and allow the use of macro-level size scale parameters for the finite element analysis. Additionally, an effective liquid conductivity is derived to capture the effects of fluid dynamics and advective transport effects within the melt pool and more accurately predict melt pool geometries without the need for coupled computational fluid dynamics analyses governing the melt pool. Experimental validations in Inconel at beam powers of 150W, 200W and 300W were performed. Inclusion of effective liquid conductivity resulting in simulation results becoming an average of 40% closer to experimental melt pool measurements
Romano, John P. II, "Thermal Transport and Melt Pool Geometry in Metallic Powder Bed Additive Manufacturing Processes for Various Novel Engineering Materials" (2015). Master's Theses. 853.
Dr. Leila Ladani