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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Composite ingot casting

A method and system for continuously or semicontinuously casting a composite metal article, such as a structurally composite ingot or the like, wherein one of the principal structural components of the ingot comprises an aluminum-lithium alloy. During such casting by a D.C. (direct chill) conventional tubular mold or electromagnetic process, the aluminum-lithium structural component of a structurally composite ingot is encircled or peripherally encased by a· further outer metal cladding component that can be cast simultaneously with the aluminum-lithium component such as another outer aluminous alloy from which lithium is absent as a constituent or impurity, although it may be present and tolerated as a trace element. In this arrangement the aluminum-lithium structural component is prevented during casting from coming into direct contact with the chilling coolant, normally water, with which lithium can react violently. Only the outer aluminous alloy envelope is subjected to the direct contact of a liquid coolant whereby as it solidifies, this outer envelope or . peripheral sheath acts as an impervious secondary mold for and protects the inner aluminum--lithium alloy structural component which is then directly controllably chilled and solidified.

George J Binczewski↗
DOE OSTI2024

Covalent Triazine-Based Frameworks with Ru-tda Based Catalyst Anchored via Coordination Bond for Photoinduced Water Oxidation

Light-induced water splitting (hν-WS) for the production of hydrogen as a solar fuel is considered a promising sustainable strategy for the replacement of fossil fuels. An efficient system for hν-WS involves a photoactive material that, upon shining light, is capable of separating and transferring charges to catalysts for the hydrogen and oxygen evolution processes. Covalent triazine-based frameworks (CTFs) represent an interesting class of 2D organic light-absorbing materials that have recently emerged thanks to their tunable structural, optical and morphological properties. Typically, catalysts (Cat) are metallic nanoparticles generated in situ after photoelectroreduction of metal precursors or directly drop-casted on top of the CTF material to generate Cat-CTF assemblies. Here, in this work, the synthesis, characterization and photocatalytic performance of a novel hybrid material, Ru-CTF, is reported, based on a CTF structure featuring dangling pyridyl groups that allow the Ru-tda (tda is [2,2':6',2'“-terpyridine]-6,6'”-dicarboxylic acid) water oxidation catalyst (WOC) unit to coordinate via covalent bond. The Ru-CTF molecular hybrid material can carry out the light-induced water oxidation reaction efficiently at neutral pH, reaching values of maximum TOF of 17 h -1 and TONs in the range of 220 using sodium persulfate as a sacrificial electron acceptor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Development of low-cost directionally-solidified turbine blades

A low-cost directionally solidified (DS) casting of turbine blades of high stress rupture is discussed. The process uses an exothermically heated mold; a newly designed solid blade was cast for the high-pressure turbine of the TFE731-3 turbofan engine. Ni-based alloys Mar-M 247 and Mar-M 200 + Hf were used. The solid DS blade replaced a conventionally cast IN100 component; a 40% cost saving is expected, with a 2.4% reduction in the takeoff specific fuel consumption. The DS Mar-M 247 blade has been selected for production in the TFE731-3B-100, and advanced version of the TFE731-3.

Hoppin, G. S., III↗
NASA NTRS1982

Constitutive model development for isotropic materials

The objective is to develop a unified constitutive model for finite-element structural analysis of turbine engine hot section components. This effort constitutes a different approach for nonlinear finite-element computer codes which were heretofore based on classical inelastic methods. A unified constitutive theory will avoid the simplifying assumptions of classical theory and should more accurately represent the behavior of superalloy materials under cyclic loading conditions and high temperature environments. Model development will be directed toward isotropic, cast nickel-base alloys used for aircooled turbine blades and vanes. The contractor will select a base material for model development and an alternate material for verification purposes from a list of three alloys specified by NASA. The candidate alloys represent a cross-section of turbine blade and vane materials of interest to both large and small size engine manufacturers. Material stock for the base and alternate materials will be supplied to the Contractor by the government.

Kaufman, A.↗
NASA NTRS1985

Cyclic Structural Analyses of SSME Turbine Blades

The problems of calculating the structural response of high-temperature space propulsion components such as turbine blades for the fuel turbopump are addressed. The first high-pressure-stage fuel turbine blade (HPFTB) in the liquid-hydrogen turbopump of the space shuttle main engine (SSME) was selected for this study. In the past these blades have cracked in the blade shank region and at the airfoil leading edge adjacent to the platform. To achieve the necessary durability, these blades are currently being cast by using directional solidification. Single-crystal alloys are also being investigated for future SSME applications. The study evaluated the utility of advanced structural analysis methods in assessing the low-cycle fatigue lives of these anisotropic components. The turbine blade airfoil of the high-pressure stage of the SSME fuel turbopump was analyzed because it has a history of rapid crack initiation.

Kaufman, A.↗
NASA NTRS1985

Graphite formation in cast iron, phase 2

Several types of cast irons are directionally solidified aboard the KC-135 aircraft. Also, control samples are run on Earth for comparison. Some of these samples are unusable because of various mechanical problems; the analysis and the interpretation of results on the samples that are run successfully is discussed.

Stefanescu, D. M.↗
NASA NTRS1996

Preliminary work toward the development of a dimensional tolerance standard for rapid prototyping

Rapid prototyping is a new technology for building parts quickly from CAD models. It works by slicing a CAD model into layers, then by building a model of the part one layer at a time. Since most parts can be sliced, most parts can be modeled using rapid prototyping. The layers themselves are created in a number of different ways - by using a laser to cure a layer of an epoxy or a resin, by depositing a layer of plastic or wax upon a surface, by using a laser to sinter a layer of powder, or by using a laser to cut a layer of paper. Rapid prototyping (RP) is new, and a standard part for use in comparing dimensional tolerances has not yet been chosen and accepted by ASTM (the American Society for Testing Materials). Such a part is needed when RP is used to build parts for investment casting or for direct use. The objective of this project was to start the development of a standard part by using statistical techniques to choose the features of the part which show curl - the vertical deviation of a part from its intended horizontal plane.

Kennedy, W. J.↗
NASA NTRS2004

Structural Benchmark Testing of Superalloy Lattice Block Subelements Completed

Superalloy lattice block panels, which are produced directly by investment casting, are composed of thin ligaments arranged in three-dimensional triangulated trusslike structures (see the preceding figure). Optionally, solid panel face sheets can be formed integrally during casting. In either form, lattice block panels can easily be produced with weights less than 25 percent of the mass of a solid panel. Inconel 718 (IN 718) and MarM-247 superalloy lattice block panels have been developed under NASA's Ultra-Efficient Engine Technology Project and Higher Operating Temperature Propulsion Components Project to take advantage of the superalloys' high strength and elevated temperature capability with the inherent light weight and high stiffness of the lattice architecture (ref. 1). These characteristics are important in the future development of turbine engine components. Casting quality and structural efficiency were evaluated experimentally using small beam specimens machined from the cast and heat treated 140- by 300- by 11-mm panels. The matrix of specimens included samples of each superalloy in both open-celled and single-face-sheet configurations, machined from longitudinal, transverse, and diagonal panel orientations. Thirty-five beam subelements were tested in Glenn's Life Prediction Branch's material test machine at room temperature and 650 C under both static (see the following photograph) and cyclic load conditions. Surprisingly, test results exceeded initial linear elastic analytical predictions. This was likely a result of the formation of plastic hinges and redundancies inherent in lattice block geometry, which was not considered in the finite element models. The value of a single face sheet was demonstrated by increased bending moment capacity, where the face sheet simultaneously increased the gross section modulus and braced the compression ligaments against early buckling as seen in open-cell specimens. Preexisting flaws in specimens were not a discriminator in flexural, shear, or stiffness measurements, again because of redundant load paths available in the lattice block structure. Early test results are available in references 2 and 3; more complete analyses are scheduled for publication in 2004.

Source record↗
NASA NTRS2008

Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions

The Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MSL-CETSOL and MICAST) are two investigations which supports research into metallurgical solidification, semiconductor crystal growth (Bridgman and zone melting), and measurement of thermo-physical properties of materials. This is a cooperative investigation with the European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) for accommodation and operation aboard the International Space Station (ISS). Research Summary: Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing (CETSOL) and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST) are two complementary investigations which will examine different growth patterns and evolution of microstructures during crystallization of metallic alloys in microgravity. The aim of these experiments is to deepen the quantitative understanding of the physical principles that govern solidification processes in cast alloys by directional solidification.

Gandin, Charles-Andre↗
NASA NTRS1980

A silicon sheet casting experiment

The casting of silicon blanks for solar cells directly without slicing is an exciting concept. An experiment was performed to investigate the feasibility of developing a machine that casts wafers directly. A Czochralski furnace was modified to accept a graphite ingot-simulating fixture. Silicon was melted in the middle of the ingot simulator in a boron nitride mold. Sample castings showed reasonable crystal size. Solar cells were made from the cast blanks. The performance is reported.

Bickler, D. B.↗
DOE OSTI2020

Imaging transient solidification behavior

Solidification processing offers the first opportunity to control microstructure, properties, and performance in metallic alloy components. Until recently, microstructural evaluations were limited to post-solidification characterization by destructive methods. We review the development of time-resolved, in situimaging techniques capable of capturing solid-liquid interfacial evolution in metallic alloys with high spatial and temporal resolution underdiverse solidification conditions relevant for applications ranging from conventional directional solidification, crystal growth, and casting,to welding and additive manufacturing. These experiments enable direct visualization of transient behaviors that would otherwise remain unknown, uniquely providinginsights into the physics that impact microstructure and defect development and strategies for microstructuralcontrol and defect mitigation. Understanding microstructural evolution and the characteristics that form under various solidification conditions is essential for the development of multiscale, experimentallyinformed predictive modeling. This is highlightedby solidification simulations that utilize in situmeasurements of solidification dynamics from state-of-the-art experimental techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Creep Behavior of a High-$\gamma^{\prime}$ Ni-Based Superalloy Fabricated via Electron Beam Melting

Additive manufacturing enables the fabrication of complex engineering components previously inaccessible through traditional processes. Nickel-base superalloys with large γ' volume fraction are typically considered non-weldable and therefore exhibit a propensity for cracking during the fusion process. These crack-prone materials, however, are of great importance in gas turbine engines due to their excellent high temperature creep resistance. In this study we investigate the creep behavior of IN738LC produced by the electron beam melting process. Here, we find that with appropriate post-build heat treatment the creep response of material oriented in the build direction exhibits deformation and rupture behavior comparable to that of conventionally cast IN738 & IN738LC. In the transverse direction properties fall below the expected cast behavior, however, we argue this is likely due to differences in grain scale and crystallographic texture. It may be possible to coarsen the grain morphology with appropriate process-parameter optimization in order to reduce the severity of intergranular fracture in the transverse direction. These results illustrate that high temperature properties exhibited by additively manufactured IN738LC are suitable for the hot section of gas turbine engines.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Microstructural variations induced by gravity level during directional solidification of near-eutectic iron-carbon type alloys

The effects of gravity on the microstructure of directionally solidified near-eutectic cast irons are studied, using a Bridgman-type automatic directional solidification furnace aboard a NASA KC-135 aircraft which flies parabolic arcs and generates alternating periods of low-g (0.01 to 0.001 g, 30 seconds long) and high-g (1.8 g, 1.5 minutes long). Results show a refinement of the interlamellar spacing of the eutectic during low-g processing of metastable Fe-C eutectic alloys. Low-g processing of stable Fe-C-Si eutectic alloys (lamellar or spheroidal graphic) results in a coarsening of the eutectic grain structure. Secondary dendrite arm spacing of austenite increases in low-g and decreases in high-g. The effectiveness of low-gravity in the removal of buoyancy-driven graphite phase segregation is demonstrated.

Stefanescu, Doru M.↗
NASA NTRS1982

Part 1: Silicon ingot casting. Heat Exchanger Method (HEM)

Directional solidification by the Heat Exchanger Method (HEM) is a viable approach for directional solidification of silicon ingots used for terrestrial solar cell applications. Some of the significant advances made during this phase of the program were: ingot size, 34 cm x 34 cm x 17 cm - 45 kg, usable material yield - 90%, solar cell efficiency averaged over the whole ingot - 85% of control CZ (35 kg ingot), very uniform resistivity over the boule, and cycle time for 36 kg ingots - 56 hours. Some of the problems encountered were growth rate decrease with increased ingot height, silicon carbide precipitates, and high dislocation density in HEM material. The silicon carbide is attributed to backstreaming of oil vapors from the vacuum pump; the high dislocation density is associated with the thermal history of the boule.

Source record↗
DOE OSTI2023

Results from a controlled depleted uranium metal casting experiment designed to investigate nuclear Forensic Radiochronometry Signatures

The accurate interpretation of uranium metal 230 Th/ 234 U and 231 Pa/ 235 U radiochronometry model ages requires an understanding of how uranium parent nuclides and decay progeny ( 230 Th and 231 Pa) behave during uranium metal casting. In order to directly measure the spatial distribution of 230 Th and 231 Pa in uranium metal before and after vacuum induction melting (VIM), Los Alamos National Laboratory identified uranium metal feedstock, characterized the metal feedstock, conducted a controlled casting experiment of an approximately 120 kg uranium metal rod, and characterized the cast metal. Herein this study presents radiochronometry results and quantified 230 Th and 231 Pa VIM separation factors from bulk uranium.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
NASA NTRS1993

Test results from a simple, low-cost, pressure-fed liquid hydrogen/liquid oxygen rocket combustor

A simple, low-cost rocket engine was designed, fabricated, and successfully hot fire tested over a wide range of interface conditions and operating parameters. The engine used low enthalpy hydrogen (45 to 70 R, 200 to 390 psia) and oxygen (139 to 163 R, 210 to 480 psia) propellants pressure-fed directly from facility cryogenic tanks. The engine demonstrated excellent performance, with 97% average combustion efficiency, and absence of combustion instabilities. Engine design chamber pressure was 300 psia, yielding about 16,500 pounds thrust at sea level with a 3:1 expansion ration test nozzle. The engine used a fixed-element injector based on TRW's unique coaxial pintle design, but was operated at 60%, 80%, and 100% thrust levels by throttling facility propellant valves. The engine was tested at propellant mixture ratios (O/F) from 5.8 to 8.4; design O/F was 6.6. To document combustion stability, in five tests RDX explosive pulse guns were detonated in radial and tangential directions across the combustion chamber during steady-state operation. The largest disturbance consisted of simultaneous detonation of a 20-grain radial gun and a 40-grain tangential gun. In no case was an instability, either feed system mode or chamber acoustic mode, excited. High-frequency piezoelectric pressure transducers documented stable recovery from disturbance overpressures within 40 milliseconds of peak pressure. A total of 67 firing tests, accumulating 149 seconds of firing time above 10% P(sub c), were performed. Since parametric testing required run durations of only 2 to 3 seconds, a heat sink combustion chamber was employed for most runs. To evaluate the feasibility of a low-cost ablative system for a flight engine design, one 20-second continuous firing was conducted with a silicone rubber chamber/throat/nozzle liner cast in one piece directly into the engine. The ablative engine operated at the equivalent of 309 seconds sea level specific impulse, when adjusted to a 98% efficient 6:1 expansion ration nozzle, and 430 seconds vacuum specific impulse, when adjusted to a 98% efficient 50:1 expansion ratio nozzle. This engine and test series represent an initial subscale demonstration of a new booster-class engine that eliminates the cost and complexity associated with regenerative cooling and typical engine cycles. This paper presents a description of the engine design and discussion and summary data plots of the performance measured during the parametric testing.

Dressler, G. A.↗
DOE OSTI2023

MFA-DVR: direct volume rendering of MFA models

3D volume rendering is widely used to reveal insightful intrinsic patterns of volumetric datasets across many domains. However, the complex structures and varying scales of volumetric data can make efficiently generating high-quality volume rendering results a challenging task. Multivariate functional approximation (MFA) is a new data model that addresses some of the critical challenges: high-order evaluation of both value and derivative anywhere in the spatial domain, compact representation for large-scale volumetric data, and uniform representation of both structured and unstructured data. Here, in this paper, we present MFA-DVR, the first direct volume rendering pipeline utilizing the MFA model, for both structured and unstructured volumetric datasets. We demonstrate improved rendering quality using MFA-DVR on both synthetic and real datasets through a comparative study. We show that MFA-DVR not only generates more faithful volume rendering than using local filters but also performs faster on high-order interpolations on structured and unstructured datasets. MFA-DVR is implemented in the existing volume rendering pipeline of the Visualization Toolkit (VTK) to be accessible by the scientific visualization community.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1986

Forging Oxide-Dispersion-Strengthened Superalloys

Cladding of mild steel prevents surface cracking when alloy contacts die. Continual need for improvements in properties of alloys capable of withstanding elevated temperatures. Accomplished by using oxide-dispersion-strengthed superalloys such as Inconel Alloy MA 6000. Elevated tensile properties of forged alloy equal those of hot-rolled MA 6000 bar. Stress-rupture properties somewhat lower than those of bar stock but, at 1,100 degrees C, exceed those of strongest commercial single crystal, directionally solidified and conventionally cast superalloys.

Harf, F. H.↗