2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Modeling Methods, Metrology, and Applications
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 8:00 AM
August 13, 2024
Room: 417 AB
Location: Hilton Austin
Session Chair: Nathaniel Wood, Air Force Research Laboratory
8:00 AM Cancelled
Two-Color Thermal Imaging and Modeling of WC-Ni Cermet Melt Pools in Laser Powder Bed Fusion: Guadalupe Quirarte1; Alexander Myers1; Alex Gourley1; B. Jayan1; Jack Beuth1; Jonathan Malen1; 1Carnegie Mellon University
Cemented carbides such as Tungsten Carbide (WC) are known for their use in resilient wear-resistant applications. However, conventional manufacturing WC can become cost and time ineffective. Additive manufacturing (AM) is a favorable method for cemented carbide manufacturing with complex geometries and less cost and time intensive compared to alternate techniques. This project applies a method to measure cemented tungsten carbide (WC)-17 wt.% nickel (Ni) composite melt pool temperatures in laser powder bed fusion (L-PBF) using a high-speed color camera two-color method technique. Using the two-color method, melt pool thermal maps of WC-Ni were captured with varying process parameters. Thermal models for the cermet composite were validated by the images to understand the underlying physics taking place in the melt pools. Melt pool temperatures exceeding melting of WC and Ni were observed. The steps taken to thermal model WC-Ni can be applied to other composite materials.
8:20 AM
High Temperature Thermal Conductivity Measurement Using Two-Color Thermal Imaging: Jonathan Malen1; Hao-Yuan Cheng1; Alexander Myers1; 1Carnegie Mellon University
We describe the development of a methodology to measure the thermal conductivity of AM materials at ultra-high temperatures (up to 4000 K). We use a two-color thermal imaging technique with a commercial color camera to measure the temperature distribution on a sample heated by a stationary laser heat source in a Directed Energy Deposition (DED) additive manufacturing machine. The radial temperature distribution is fit to a solution to the heat diffusion equation where the temperature dependent thermal conductivity is used as a fitting parameter. We evaluate the robustness of our proposed method using reference materials with known high temperature thermal conductivity, including Tungsten, Tungsten Carbide, and Tantalum. Unlike current pulse methods that have been previously used, our laser based approach is applicable to electrical insulators. Temperature dependent thermal conductivities are critical to optimize and understand AM processes and also for aerospace and energy applications with extreme environments.
8:40 AM
Synchrotron-based In Situ/Operando Characterization Capabilities at NSLS-II: Zhongshu Ren1; Xianghui Xiao1; Mingyuan Ge1; Yong Chu1; 1National Synchrotron Light Source II, Brookhaven National Laboratory
High-resolution non-intrusive characterization techniques are highly desired for understanding additive manufacturing processes, which is critical for optimization and improving part qualities. In this presentation, we will introduce a few advanced characterization capabilities at the National Light Source II (NSLS-II) and focus on one Full-field X-ray Imaging (FXI) beamline. This beamline operates a transmission X-ray microscope (TXM) that provides state-of-art X-ray nano-scale imaging capability at resolutions in the tens of nanometers range. With capabilities for the fastest tomography and x-ray absorption edge spectroscopy (XANES) in the world, nano-scale morphology and chemical composition can be quickly obtained. Through NSLS-II’s recapitalization and upgrade program, new capabilities such as laminography and fluorescence will be integrated into FXI. These advanced capabilities open new pathways and show great potential for enhancing the characterization of additive manufacturing processes, particularly under an in situ/operando conditions.
9:00 AM
Predicting Surface Roughness in Laser Powder Bed Fusion Parts after Laser Polishing: A Multi-Physics Simulation Approach: Hong-Chuong Tran1; Dac-Phuc Pham2; Duc-Kien Hoang1; 1National Taipei University of Technology; 2Southern Taiwan University of Technology
Laser powder bed fusion (L-PBF) uses a controlled laser beam to melt specific regions of a metal powder bed in a layer-by-layer fashion to fabricate parts with an intricate geometry. However, due to the stochastic nature of the L-PBF process, many defects may occur during the build process, including distortion, porosity, and high surface roughness. A poor roughness of the upper surface is frequently associated with impaired mechanical properties and a lower corrosion resistance. Thus, laser polishing (LP) is commonly employed to smooth the surface of the component following the build process. The present study proposes an integrated framework based on discrete element method (DEM) and computational fluid dynamics (CFD) simulations to predict the final surface morphology and roughness of L-PBF components following LP processing. The validity of the simulation model is confirmed by comparing the calculated mean surface roughness of the polished components (S_a) with the experimental values.
9:20 AM
The Effects of Laser Absorption and Shielding in Plasma Vapor Jets Induced by Continuous Wave Laser Irradiation of Tungsten: Michael Stokes1; Alexey Volkov1; Saad Khairallah2; 1University of Alabama; 2Lawrence Livermore National Laboratory
Laser powder bed fusion (L-PBF) experiments show that absorption of laser radiation by the evaporated vapor jet can negatively impact print quality at high laser powers. This plasma shielding becomes more prevalent during the processing of refractory metals used in high-entropy alloys due to the high laser intensity that is required for melting. The present work numerically investigates the effect of plasma formation in the evaporated jet from bulk tungsten targets for various laser powers using an in-house, hybrid computational model. The model combines a non-equilibrium collision-radiation model of ionization and absorption with the direct simulation Monte Carlo (DSMC) method. The simulations reveal the range of conditions where radiation absorption in the jet strongly affects the thermal state of the irradiated target. Under conditions typical for L-PBF, the simulations indicate that a supersonic vapor microjet is formed and the plasma shielding effect is strong. LLNL-ABS-863662
9:40 AM Break
10:00 AM Cancelled
Front Assaulting an Impregnable Monge-Ampere Strong Explicit Solution for Non-Axially Symmetrical Freeform Surfaces with Prescribed Bivariate Curvature Tensor Extending Over a Complete R3 Riemann Sphere: BenZion Inditsky1; 1Visual Photonics Ltd
“Out of intense complexities, intense simplicities emerge.” Winston Churchill Monge-Ampere PDE is the most important fundamental unsolved problem of Differential geometry. The very notion of DF becomes murky and undefined. Over the last five decades, SCG has developed a multitude of “weak” methods to circumvent this problem all of which substitute a direct algebraic curvature-defined surface synthesis by fitting or/and deforming an existing cloud point array. Obviously, these operations do not preserve Curvature (CV). At the best, they can produce integrable smooth surface with continuous CV over a patch or its edges.The paper includes numerous (patented) examples of novel, yet unknown or deemed impossible shapes relating to accurate optical lenses and lightguides, biomimicry inspired human and animal organ shapes, architectural domes It is concluded by a number of statements that are more theoretical with far-reaching implications to manifolds, classes of integrable surfaces, affinity and morphing invariants etc
10:20 AM
Investigating the Effect of Workpiece Shape on Thermal History and Coating Properties in High-Speed Coatings Using Laser Directed Energy Deposition: Shiho Takemura1; Takanori Mori2; Yoko Hirono2; Yasuhiro Kakinuma1; 1Keio University; 2DMG MORI CO., LTD.
Directed Energy Deposition (DED) can be used for metal coating as well as parts fabrication because it can supply powder and laser on the part surface freely. As for high-speed coating using DED, it has advantages such as high efficiency and reduced heat-affected zone. However, because of rapid heat input and cooling, it is considered that the thermal history of the coating layer becomes more sensitive to the coated workpiece shape, which can affect the coating properties. In this research, the effect of workpiece shape on thermal history during high-speed coating using DED is numerically analyzed. A thermal simulation of rotational coating is developed, where elements are added and the heat input area is moved according to laser scanning and workpiece rotation. Additionally, experiments are conducted to investigate the relationship between thermal history and coating quality and hardness. In this study, solid and hollow cylinders are selected as workpieces.
10:40 AM
Towards Experimentally-Informed Modeling of Conduction for Improved Finite Element Thermal Prediction of Wire-Arc Directed Energy Deposition: Ally Cummings1; Walker Jarrell1; Matthew Priddy1; 1Center for Advanced Vehicular Systems, Mississippi State University
Wire-arc directed energy deposition (arc-DED) is a metal-based additive manufacturing process known for its high deposition rates, which enable the production of medium to large-scale components. Due to the cyclic heating and cooling associated with this process, residual stresses and distortion are experienced within the part. Finite element analysis (FEA) can be used to predict the thermomechanical response of parts printed using arc-DED. FE models have previously consisted of the part and substrate with boundary conditions representing effects of the assembly to minimize computational time. However, these boundary conditions are not physically motivated, but rather calibrated to match experimental data. This work explores a more informed modeling approach that includes the assembly to accurately simulate conductive heat transfer, which is known to play a significant role in the thermal profile of the part. This model offers improved thermal predictions and increased repeatability across different parts by reducing model calibration requirements.
11:00 AM
Toward Parametric Heat Transfer Solvers in Additive Manufacturing: Akshay Jacob Thomas1; Eduardo Barocio1; Ilias Bilionis1; R. Byron Pipes1; 1Purdue University
Physics-informed neural networks (PINNs) have recently been a popular framework to integrate experimental data and physics-based constraints specified via partial differential equations. However, the application of PINNs to additive manufacturing is limited since a suitable physics-based loss function is missing for geometries that evolve. The objective of this work is to address this gap. We propose a loss function for PINNs to solve the heat transfer equation on evolving geometries without mesh-based discretization. We use our methodology to predict the temperature evolution as a single bead is being deposited. We consider various cases of mixed Dirichlet, and Neumann boundary conditions and compare our results to finite element simulations. We also present guidelines to obtain consistent results using the proposed method. We finally discuss the potential of our method in solving parametric heat transfer problems in additive manufacturing.
11:20 AM
Impact of Weld-Bead Profile Approximations on Thermal Finite Element Analysis for Wire-Arc Directed Energy Deposition: Jeffery Betts1; Ryan Stokes1; Matthew Priddy1; 1Mississippi State University
Finite element analysis (FEA) of wire arc directed energy deposition (arc-DED) traditionally assumes an approximate weld bead profile. However, there are multiple methods to determine the approximate weld profile, and the differences between them are not known. The overall bead width and height is the most common approximation, but often leads to overestimating the cross-sectional area. Instead this work utilizes thermal FEA with the Goldak Double Ellipsoidal Heat Source to predict the thermal history, and investigate the effects of varying weld-bead shape, height, width, and cross-sectional area to determine the approximate weld-bead profile. Optical profilometry was utilized to measure a series of bead-on-plate welds using ER70S-6 and cold metal transfer (CMT) to inform the approximate weld bead profile. Understanding the relationship between the weld-bead profile and predicted thermal history is critical to improve the accuracy and predictive capabilities of current arc-DED FEA frameworks.
11:40 AM
Microstructure-Informed Thermal-Mechanical Simulation of Multi-Bead Structures for Large Area Additive Manufacturing Polymer Composite Extrusion/Deposition: Neshat Sayah1; Aigbe Awenlimobor1; Douglas Smith1; 1Baylor University
Large scale polymer extrusion/deposition has emerged as a preferred manufacturing technology for making large parts where carbon fiber filled materials are employed to reduce thermal expansion and increase strength and stiffness. This presentation simulates the thermal history and its effect on residual stress while printing multi-bead columns of carbon fiber ABS on a large scale additive manufacturing (LAAM) system. A finite element model is presented which uses element addition to include new bead layers during the process simulation. Bead geometries and void and fiber content throughout the beads are measured with microCT scanning where specific focus is given to computing the spatially varying thermal-mechanical properties from the bead microstructure. Results show the effect of bead position and surface convection on bead temperatures and stress. Bead adhesion calculations are also provided to expose the significant effect that bead microstructure has on bead interface temperature, stress, and degree of adhesion.