Additive Manufacturing Benchmarks 2022 (AM-Bench 2022): Melt-Pool Scale II
Program Organizers: Brandon Lane, National Institute of Standards and Technology; Lyle Levine, National Institute of Standards and Technology
Wednesday 1:30 PM
August 17, 2022
Room: Old Georgetown Room
Location: Hyatt Regency Bethesda
Session Chair: Jason Fox, National Institute of Standards and Technology
1:30 PM Invited
Topographic Measurements of Laser Tracks in Alloy 725 Bare Plate for an Additive Manufacturing Benchmark: Richard Ricker1; David Deisenroth1; Brandon Lane1; Jordan Weaver1; Lyle Levine1; 1National Institute of Standards and Technology
Additive manufacturing of metals by powder bed fusion (PBF) is a process where a laser traverses a powder covered surface melting the powder and enough of the substrate to insure mixing and complete fusion after solidification. The layer of powder in this process adds a considerable amount of complexity. Therefore, a benchmark that incorporates the complexities of alloy melting and solidification, but without the stochastic influences of the powder layer, will benefit model development and validation. The objective of this work was to provide a benchmark for this type of process by measuring the topography of tracks created in bare alloy 725 plate by a laser traversing the surface with different energies and velocities. The surface topography was measured and quantified using confocal scanning laser microscopy. These results will be presented, discussed, and compared to similar measurements on Alloy 625 and other alloy systems.
2:00 PM
Characterization of Laser Powder Bed Fusion Surfaces: Edwin Glaubitz1; Joy Gockel1; Jason Fox2; Orion Kafka2; 1Colorado School of Mines; 2National Institute of Standards and Technology
Surfaces of components fabricated using additive manufacturing (AM) often have a more complex surface than those built using conventional methods. In addition to the layered nature of the surfaces, there are features of the AM surface such as adhered powder or spatter particles which may not influence the mechanical performance of a component but will influence surface roughness metrics. A better understanding of measurement techniques, as well as how surface features influence surface roughness metrics is needed to improve the characterization and understanding of AM surfaces. The surfaces of specimens built using laser powder bed fusion (LPBF) AM from multiple standard materials such as nickel superalloys, steels, and aluminum are measured using several non-destructive techniques. Relationships between measurement techniques, measurement post-processing, and surface roughness will be discussed. An increased understanding of surface measurement techniques will inform future studies to determine parameter and properties relationships to surface roughness of AM components.
2:20 PM
(On-Demand) Investigation of Particle Dynamics During Laser Powder Bed Fusion via a Novel Smooth Particle Hydrodynamics Modeling Approach: Christoph Meier1; Patrick Praegla1; Reimar Weissbach2; John Hart2; Wolfgang Wall1; 1Technical University of Munich; 2Massachusetts Institute of Technology
Melt pool dynamics in laser powder bed fusion (LPBF) are highly dynamic and include particle redistribution and denudation, and ejection of spatter. These effects are inherent to the nominal process, yet can lead to defects in the final part. For computational models of LPBF to give the most useful insights, it is necessary to accurately represent the fluid and gas flows, interface forces, and powder dynamics. We have developed a novel model for thermo-capillary phase change problems that considers the full range of relevant interface forces at the melt pool surface, explicitly resolves the atmospheric gas phase, and models mobile powder particles. Using this model, we investigate the influence of powder cohesiveness on melt pool and powder dynamics, and focus on evaporation-induced powder material redistribution and particle ejection. Our results also show how powder mobility and melt track uniformity are related to layer quality (e.g., packing density).
2:40 PM
Mixed Interface-capturing/Interface-tracking Formulation for Metal Additive Manufacturing on NIST 22 Benchmark Challenge Problems: Qiming Zhu1; Jinhui Yan; 1University of Illinois Urbana-Champaign
High fidelity thermal multi-phase flow simulations are in much demand to reveal the multi-scale and multi-physics phenomena in metal additive manufacturing (AM) processes, yet accurate and robust predictions remain challenging. In this paper, we present a novel computational framework by mixing interface-capturing/interface-tracking methods for simulating the thermal multi-phase flows in metal AM applications, focusing on better handling the gas-metal interface, where AM physics, such as phase transitions and laser-material interaction, mainly takes place. The framework, built on the level set method and variational multi-scale formulation (VMS), features three major contributions:1. A simple computational geometry-based re-initialization approach, which maintains excellent signed distance property on unstructured meshes, re-constructs an explicit representation of gas-metal interface from the level set, and facilitates the treatment of the multiple laser reflections during keyhole evolution in AM processes.
3:00 PM Break