Additive Manufacturing of Metals:
ICME Gaps: Material Property and Validation Data to Support Certification: Data Needs for Simulation: Material Property and Validation Data to Support Certification
Sponsored by: TMS: Integrated Computational Materials Engineering Committee, TMS Additive Manufacturing Bridge Committee
Program Organizers: Joshua Fody, NASA Langley Research Center; Edward Glaessgen, NASA Langley Research Center; Christapher Lang, NASA Langley Research Center; Greta Lindwall, KTH Royal Institute of Technology; Michael Sansoucie, Nasa Marshall Space Flight Center; Mark Stoudt, National Institute of Standards and Technology
Monday 8:00 AM
October 18, 2021
Room: A114
Location: Greater Columbus Convention Center
Session Chair: Christapher Lang, NASA Langley Research Center; Joshua Fody, NASA
8:00 AM Introductory Comments
8:10 AM Keynote
ICME Gaps for Additive Manufacturing of Metals: Anthony Rollett1; 1Carnegie Mellon University
Rapid advances in 3D printing of metals have enabled widespread used in industry. Key questions remain as to how to qualify printers and certify parts, especially in terms of defect structures. Under support from the NASA-ULI program, a multi-university team is determining process windows, characterizing microstructures and surface finish, and measuring fatigue resistance in 4-point bend fatigue. Preliminary results point to similar process windows for the same model at different locations when using a consistent source of Ti-6Al-4V powder. Microstructure and basic mechanical properties can be predicted from thermal history albeit heuristically. Transferring the methodology to an aluminum alloy in a different printer, however, required re-evaluation of melt pool sizes, which is basic to the proposed physics-based approach to qualification. Overall ICME needs include the need for computational tools that predict melt pool shape & size, melt pool stability, microstructure formation, including texture, diffusion, and solid state phase transformation.
8:50 AM
High Temperature Material Property Data and Challenges to Thermal Process Model Predictions and In-Situ/Ex-Situ Measurements for Metallic Additive Manufacturing: Joshua Fody1; Samuel Hocker1; Joseph Zalameda1; Wesley Tayon1; 1NASA Langley Research Center
Understanding and predicting as-built mechanical properties of parts produced by metallic additive manufacturing has improved significantly over the past decade; however, difficult to measure material properties and process outcomes continue to be challenges. The qualification or certification of aerospace parts require extensive measures to quantify variable properties of the parts in order to reduce the risk of component failure. The variability, inherent to the additive manufacturing process, adds unwanted uncertainty in the production of load critical structural components. Process modeling has proven valuable in providing predictions and context for understanding outcomes of the additive manufacturing process; however, these physically informed process models require material properties at temperatures that are difficult to measure and rarely available. Furthermore, calibrating or validating the process models is difficult because such ground truth data is challenging to measure. This talk will explore some of the challenges to acquiring and relating calibrated in-situ thermography and ex-situ optical microscopy measurements.
9:10 AM
Determining Data Requirements to Quantify Porosity in the Laser Powder Bed Fusion Process: Mahya Shahabi1; Caitlin Kean1; Adrianna Yuen1; Anthony Rollett2; Sneha Prabha Narra2; 1Worcester Polytechnic Institute; 2Carnegie Mellon University
Data-driven quantification of microstructure in additively manufactured parts helps establish process-structure-property relations. For instance, fatigue resistance is governed by the upper tail of the porosity distribution. However, the amount of data required to accurately populate the porosity distribution is still unknown. Towards addressing this gap, this talk discusses the data required to quantify porosity in the laser powder bed fusion (L-PBF) additively manufactured parts. 2D porosity data obtained from cross-sectional microscopy was used as an example. The minimum required number of pores was identified for multiple L-PBF specimens (varying porosity levels) to achieve a representative Generalized Pareto distribution to describe the upper tail. Our results confirm the intuition that the data required to characterize part porosity is primarily determined by the quality of the sample and the required precision of the model. Methods described here can also be applied to 3D porosity data and features such as grain size.
9:30 AM
Methods for Improved Part-scale Thermal Process Simulations in Laser Powder Bed Fusion: Seth Strayer1; Florian Dugast1; Alaaeldin Olleak1; Shawn Hinnebusch1; Joshua Fody2; Albert To1; 1University of Pittsburgh; 2National Aeronautics and Space Administration
This talk presents methodologies for improving the fidelity and accuracy of part-scale thermal process simulations using the finite element (FE) method in laser powder bed fusion (LPBF) through novel numerical algorithms and data-driven approaches. First, the demand and feasibility of part-scale LPBF thermal process simulations are discussed. Second, we will address the limitations of using a pure conduction-based FE model to simulate the complex physical mechanisms occurring during LPBF. Several existing approaches to alleviate these issues, including matrix-free method with GPU computing, heat source optimization, and anisotropically enhanced thermal properties, will be presented. We will also explore avenues for improving such techniques, highlighting the need for accurate high-temperature material properties and the pivotal role of extensive calibration and validation data.
9:50 AM
Experimental and Numerical Investigation of Pressureless Sintering for Binder Jetted Metal Parts: Kaiwen Zhang1; Wei Zhang1; Ryan Brune1; Xu Zhang1; Edward Herderick1; 1Ohio State University
In Binder Jetting Additive Manufacturing, liquid binder is deposited to join powder particles to form near-net shape parts at room temperature. The parts are subsequently sintered at high temperatures. A primary challenge for binder jetting is the large, anisotropic shrinkage resulted from sintering. In this study, a macro-scale finite element analysis considering elastic-viscoplastic constitutive behavior is developed to predict the post-sintering shape of binder jetting printed coupons made of stainless steel 316L. The constitutive equation includes both creep and volumetric swelling strain calculations. Experimentally, cantilever- and bridge-shaped coupons were printed using 316L powder and subsequently sintered. The green-state relative density was determined from the mass and volume of as-printed part. The relative density after sintering was determined by the porosity fraction measured on optical micrographs. The effect of input viscoplastic constitutive properties on the calculated quantities such as dimensional shrinkage, final relative density, and deformed shapes was discussed.