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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Microstructural Modification and Healing of Additively Manufactured Parts by Electropulsing

For many applications, the promises of additive manufacturing (AM) of rapid development cycles and fabrication of ready-to-use, geometrically-complex parts cannot be realized because of cumbersome thermal postprocessing. This postprocessing is necessary when the nonequilibrium microstructures produced by AM lead to poor material properties. This study investigated if electropulsing, the process of sending high-current-density electrical pulses through a metallic part, could be used to modify the material properties of AM parts. This process has been used to modify conventional wrought materials but has never been applied to AM materials. Two representative AM materials were examined: 316L stainless steel and A1Si10Mg. Two hours of annealing are needed to remove chemical microsegregation in AM 316L; using electropulsing, this was accomplished in 200 seconds. The ductility of AlSil0Mg parts was increased above that of the as-built material using electropulsing. This study demonstrated that electropulsing can be used to modify the microstructures of AM metals.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Detection of Defects in Additively Manufactured Metallic Materials with Machine Learning of Pulsed Thermography Images

Additive manufacturing (AM) is an emerging method for cost-efficient fabrication of nuclear reactor parts. AM of metallic structures for nuclear energy applications is currently based on laser powder bed fusion (LPBF) process, which can introduce internal material flaws, such as pores and anisotropy. Integrity of AM structures needs to be evaluated nondestructively because material flaws could lead to premature failures due to exposure to high temperature, radiation and corrosive environment in a nuclear reactor. Quality control (QC) requires nondestructive evaluation (NDE) of actual AM structures. Pulsed thermography is a potentially promising QC technique because it is scalable to arbitrary structure size. However, detection sensitivity of this method is limited by noises. We investigate separation of signal from noise in thermography images using several machine learning (ML) methods, including new spatio-temporal blind source separation (STBSS) and spatio-temporal sparse dictionary learning (STSDL) methods. Performance of the ML methods is benchmarked using thermography data obtained from imaging stainless steel 316L and Inconel 718 specimens produced LPBF method with imprinted calibrated porosity defects. The ML methods are ranked by F-score and execution runtime. The ML methods with higher accuracy require longer run time. However, this runtime is sufficiently short to perform QC within a realistic time frame.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

In Situ, Real-Time Diagnostic to Improve the Liquid Metal Jetting Additive Manufacturing Process [Poster]

Liquid Metal Jetting (LMJ) is a metal additive manufacturing technique that involves jetting molten metal droplets at high frequencies to build solid metal parts. As an alternative to industry standard Lazer Powder Bed Fusion (LPBF) and Direct Metal Writing (DMW) techniques, LMJ poses significant advantages including no powder feed stock, no post sintering process, very high deposition rates, and the capability to print various metals. This summer, I was tasked with improving my old system to process at much higher resolution, Increasing the capture rate, and implementing this diagnostic on various LMJ setups. This system provides a vital longitudinal study to understand individual droplets in the LMJ process.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Additively Manufactured Pressure Limiting Irradiation Capsule for the High Flux Isotope Reactor

The Advanced Materials and Manufacturing Technologies (AMMT) program previously demonstrated an additively manufactured (AM) irradiation capsule (commonly referred to as a “rabbit”) from 316H stainless steel (SS) for insertion into the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL)1. This report details efforts to design and fabricate an AM pressure limiting structure (PLS) into one of the end caps of a rabbit capsule and qualify it for insertion into HFIR. The PLS includes a thin cylindrical rupture wall, a shield, and internal supports to facilitate printing and ensure mechanical integrity. Its overall dimensions are 9-mm tall and 10-mm in diameter— equivalent to about one-fourth of the size of a AAA battery. The PLS maintains safe internal operating pressures for a rabbit capsule while in the reactor. Although this application is specific to HFIR, the approach lends itself to further applications in industrial, aeronautical, advanced space and power generation environments. Several PLS rabbits capsules have been successfully designed, fabricated, pressure tested, and qualified for future insertion into the HFIR for irradiation and post-irradiation evaluation.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Effect of Heat Treatment on Spallation of Additively manufactured AlSi10Mg

The eutectic alloy AlSi10Mg is commonly used for additive manufacturing (AM), as its high Si content improves printability. This abundance of Si forms Si-rich precipitates whose structure is heavily dependent on the thermal history and have been shown to strongly influence its mechanical properties. In this presentation we present the results of experiments to study the effect of the Si-structure on the equation of state and spallation strength of AM AlSi10Mg.

Elmslie, Timothy Alexander [Sandia National Labora↗
DOE OSTI2020

Binder Jetting and Sintering in Additive Manufacturing

This article focuses on binder-jetting technologies in additive manufacturing (AM) that produce metal artifacts either directly or indirectly. The intent is to focus on the most strategic and widespread uses of the binder jetting technology and review some of the challenges and opportunities for that technology. The discussion includes a historical overview and covers the major steps involved and the advantages of using the binder jetting process. The major steps of the process covered include printing, curing, de-powdering, and sintering.

Elliott, Amy↗
DOE OSTI2022

Deep Learning for In-Situ Layer Quality Monitoring during Laser-Based Directed Energy Deposition (LB-DED) Additive Manufacturing Process

Defects are a leading issue for the rejection of parts manufactured through the Directed Energy Deposition (DED) Additive Manufacturing (AM) process. In an attempt to illuminate and advance in situ quality monitoring and control of workpieces, we present an innovative data-driven method that synchronously collects sensing data and AM process parameters with a low sampling rate during the DED process. The proposed data-driven technique determines the important influences that individual printing parameters and sensing features have on prediction at the inter-layer qualification to perform feature selection. Three Machine Learning (ML) algorithms including Random Forest (RF), Support Vector Machine (SVM), and Convolutional Neural Network (CNN) are used. During post-production, a threshold is applied to detect low-density occurrences such as porosity sizes and quantities from CT scans that render individual layers acceptable or unacceptable. This information is fed to the ML models for training. Training/testing are completed offline on samples deemed “high-quality” and “low-quality”, utilizing only features recorded from the build process. CNN results show that the classification of acceptable/unacceptable layers can reach between 90% accuracy while training/testing on a “high-quality” sample and dip to 65% accuracy when trained/tested on “low-quality”/“high-quality” (respectively), indicating over-fitting but showing CNN as a promising inter-layer classifier.

36 MATERIALS SCIENCE↗
DOE OSTI2016

THE DURABILITY OF LARGE-SCALE ADDITIVE MANUFACTURING COMPOSITE MOLDS

Oak Ridge National Laboratory s Big Area Additive Manufacturing (BAAM) technology permits the rapid production of thermoplastic composite molds using a carbon fiber filled Acrylonitrile-Butadiene-Styrene (ABS) thermoplastic. Demonstration tools (i.e. 0.965 m X 0.559 m X 0.152 m) for composite part fabrication have been printed, coated, and finished with a traditional tooling gel. We present validation results demonstrating the stability of thermoplastic printed molds for room temperature Vacuum Assisted Resin Transfer Molding (VARTM) processes. Arkema s Elium thermoplastic resin was investigated with a variety of reinforcement materials. Experimental results include dimensional characterization of the tool surface using laser scanning technique following demolding of 10 parts. Thermoplastic composite molds offer rapid production compared to traditionally built thermoset molds in that near-net deposition allows direct digital production of the net geometry at production rate of 45 kg/hr.

Post, Brian K↗
DOE OSTI2016

Methods for the additive manufacturing of semiconductor and crystal materials

A method for the additive manufacturing of inorganic crystalline materials, including: physically combining a plurality of starting materials that are used to form an inorganic crystalline compound to be used as one or more of a semiconductor, scintillator, laser crystal, and optical filter; heating or melting successive regions of the combined starting materials using a directed heat source having a predetermined energy characteristic, thereby facilitating the reaction of the combined starting materials; and allowing each region of the combined starting materials to cool in a controlled manner, such that the desired inorganic crystalline compound results. The method also includes, prior to heating or melting the successive regions of the combined starting materials using the directed heat source, heating the combined starting materials to facilitate initial reaction of the combined starting materials. The method further includes translating the combined starting materials and/or the directed heat source between successive locations. The method still further includes controlling the mechanical, electrical, photonic, and/or optical properties of the inorganic crystalline compound.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Additive Manufacturing Advances to Facilitate Novel Robot and Remote System Construction

Additive manufacturing (AM), in both polymer and metal, has advanced to the point where it can substantially facilitates robot and remote system design and implementation. While AM is not a panacea to fix bad design concepts, properly used AM can creates features and capabilities otherwise not possible in machined or cast products. AM design rules are still being developed and must be applied differently based on the process and purpose of the final component, but progress is being made in practical implementation. Polymer-based AM has been commercially available commercially for quite some time and is regularly used to facilitatefor prototyping and test fitting of parts later to be before they are fabricated fromin metal or to produced in low production quantity parts that do not require high structural strength. Metal printing processes are more diverse than polymer print processes. Both polymer and metal printing systems can be used to make parts or complete systems for robotics. Two implementation examples thato illustrate the possibilities and to identify issues that remain in metal printing are: a dual arm hydraulic manipulator and a distal link of an excavator arm. The dual arm hydraulic manipulator was printed in titanium using an e-beam fusing process. All hydraulics and electrical cabling passageways were printed into the manipulator; there are no external hoses or cables. The distal link of an excavator arm was printed using a wire-fed metal inert gas process. The excavator was then used for digging as part of an equipment exposition validating the structural integrity of the printed part.

Noakes, Mark↗
DOE OSTI2020

Methods of forming structures and fissile fuel materials by additive manufacturing

A method of forming one or more structures by additive manufacturing comprises introducing a first layer of a powder mixture comprising graphite and a fuel on a surface of a substrate. The first layer is at least partially compacted and then exposed to laser radiation to form a first layer of material comprising the fuel dispersed within a graphite matrix material. At least a second layer of the powder mixture is provided over the first layer of material and exposed to laser radiation to form inter-granular bonds between the second layer and the first layer. Related structures and methods of forming one or more structures are also disclosed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Compact absorptivity measurement system for additive manufacturing

The present disclosure relates to a powdered bed fusion additive manufacturing (PBFAM) apparatus. The apparatus uses a container for holding a quantity of powdered material. The container has a bottom wall for supporting the powdered material, wherein the bottom wall is made from the same material as the powdered material. A temperature sensing subsystem is coupled to a portion of the container for detecting a temperature of the container. A laser generates an optical beam directed at the powdered material held by the container for melting the powdered material. A controller receives temperature information from the temperature sensing subsystem and determines an absorptivity of the powdered material based on the temperature information.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Chapter 6 - Polymer and composites additive manufacturing: material extrusion processes

This chapter focuses on material extrusion additive manufacturing (AM) processes for polymers and composite materials. Different extrusion AM platforms, along with their operating mechanism concepts, processing capabilities, and limitations, are discussed here. This chapter also covers state-of-the-art developments in new areas such as hybrid systems, integrated systems, and automation, which facilitate the integration of extrusion-based AM processes into smart manufacturing or Industry 4.0. Following this, a comprehensive discussion on materials development, criteria for successful printing of different materials (thermoplastics, thermosets, and their composites), key factors influencing printing, and material-related challenges in extrusion AM is presented. Finally, a brief overview of current and future potential applications of material extrusion AM technology is provided.

Kishore, Vidya↗
DOE OSTI2021

Electron Beam Powder Bed Fusion Additive Manufacturing of Refractory Metals

The processing of refractory metals via additive manufacturing (AM) presents an opportunity to fabricatecomponents not possible through traditional powder metallurgy techniques. However, processing via AM isextremely challenging and there exist a host of technological limitations still unaddressed. Molybdenumand tungsten are two materials of particular interest for nuclear energy generation applications. Themajority of existing work on the processing of these materials is focused on laser powder bed fusion whereasa smaller body of work exists for electron beam melting AM. In general, material with acceptable densitycan be obtained via both routes however cracking is much more difficult to mitigate against. Strongcrystallographic fiber textures have been observed across a range of refractory systems. In this work wepresent our recent findings on electron beam melting AM of pure tungsten and molybdenum. Wedemonstrate that defect-free material can be obtained in both systems with appropriate processing. Strongbuild direction crystallographic texture fibers are observed in both systems. In molybdenum the fibertexture has direct impact on the resulting tensile behavior. These results demonstrate that electron beamAM is a suitable technology for processing these difficult to fabricate materials.

Fernandez-Zelaia, Patxi↗
DOE OSTI2021

Method for tuning thermal expansion properties in an additive manufacturing feedstock material

A feedstock material for use in an additive manufacturing apparatus is prepared from a first material and a metal organic framework (MOF). The MOF comprises a plurality of nodes and a plurality of linkers, the plurality of linkers coupled to the plurality of nodes, thereby forming a framework. The MOF has a lower coefficient of thermal expansion than a coefficient of thermal expansion for the first material. As a result, the feedstock material has a reduced coefficient of thermal expansion as compared to the first material alone and thus exhibits low thermal expansion as its temperature is increased. The coefficient of thermal expansion for the MOF may be modified by using a different plurality of nodes and/or a different plurality of linkers, as well as by incorporating guest molecules or atoms into the framework of the MOF.

Burtch, Nicholas C.↗