Search NASA⌕ Search

SEARCH · Search NASA

Results for “Material processing flows”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Stirling Space Engine Program: Appendixes A, B, C and D - Volume 2

The objective of this program was to develop the technology necessary for operating Stirling power converters in a space environment and to demonstrate this technology in full-scale engine tests. Volume 2 of the report includes the following appendices: Appendix A: Heater Head Development (Starfish Heater Head Program, 1/10th Segment and Full-Scale Heat Pipes, and Sodium Filling and Processing); Appendix B: Component Test Power Converter (CTPC) Component Development (High-temperature Organic Materials, Heat Exchanger Fabrication, Beryllium Issues, Sodium Issues, Wear Couple Tests, Pressure Boundary Penetrations, Heating System Heaters, and Cooler Flow Test); Appendix C: Udimet Testing (Selection of the Reference Material for the Space Stirling Engine Heater Head, Udimet 720LI Creep Test Result Update, Final Summary of Space Stirling Endurance Engine Udimet 720L1 Fatigue Testing Results, Udimet 720l1 Weld Development Summary, and Udimet 720L1 Creep Test Final Results Summary), and Appendix D: CTPC Component Development Photos.

Dhar, Manmohan↗
NASA NTRS2009

Improvements in Production of Single-Walled Carbon Nanotubes

A continuing program of research and development has been directed toward improvement of a prior batch process in which single-walled carbon nanotubes are formed by catalytic disproportionation of carbon monoxide in a fluidized-bed reactor. The overall effect of the improvements has been to make progress toward converting the process from a batch mode to a continuous mode and to scaling of production to larger quantities. Efforts have also been made to optimize associated purification and dispersion post processes to make them effective at large scales and to investigate means of incorporating the purified products into composite materials. The ultimate purpose of the program is to enable the production of high-quality single-walled carbon nanotubes in quantities large enough and at costs low enough to foster the further development of practical applications. The fluidized bed used in this process contains mixed-metal catalyst particles. The choice of the catalyst and the operating conditions is such that the yield of single-walled carbon nanotubes, relative to all forms of carbon (including carbon fibers, multi-walled carbon nanotubes, and graphite) produced in the disproportionation reaction is more than 90 weight percent. After the reaction, the nanotubes are dispersed in various solvents in preparation for end use, which typically involves blending into a plastic, ceramic, or other matrix to form a composite material. Notwithstanding the batch nature of the unmodified prior fluidized-bed process, the fluidized-bed reactor operates in a continuous mode during the process. The operation is almost entirely automated, utilizing mass flow controllers, a control computer running software specific to the process, and other equipment. Moreover, an important inherent advantage of fluidized- bed reactors in general is that solid particles can be added to and removed from fluidized beds during operation. For these reasons, the process and equipment were amenable to modification for conversion from batch to continuous production.

Balzano, Leandro↗
NASA NTRS2021

Phase Change Processes for Thermal Management Systems and Science Investigations

This white paper focuses on the scientific rationale and motivation for deploying phase change processes-based spacecraft thermal management systems for space missions [1,2]. Phase change processes need to be implemented in the design of various life support systems, sub-critical cryogenic and thermal control systems, taking advantage of the latent heat of phase change so as to significantly increase the heat transfer rate per unit fluid mass. Experimental data are critical to understanding gravitational effects on complex phase change processes using novel materials and working fluids. Experimental data can be acquired by either designing new testing platforms or performing experiments with simulant fluids on existing microgravity platforms. With the acquired data, theoretical flow physics models and numerical simulations can then be validated for use under long-duration microgravity conditions. The acquired data and validated models will enable the deployment of game-changing thermal management systems with remarkably improved efficiency and stability in heat acquisition, transport, and rejection for long-duration space missions.

Fluid mechanics↗
NASA NTRS1984

Geomorphic clues to the Martian volatile inventory. 1: Flow ejecta blankets

There are classes of landforms whose presence on Mars is strongly suggestive, if not confirmatory, of the participation of volatiles, presumably water, in its geomorphic development: (1) valley networks, (2) outflow channels, (3) landslides, and (4) flow-ejecta blankets. The first two may represent landforms generated by the movement of volatiles from sources, while the latter two probably represent the dissipation of energy generated by forcing inputs (e.g., kinetic energy and gravity) modulated by volatiles. In many areas on Mars, all four processes have acted on the same lithologic materials and were influenced by the composition of those units, and possibility by the climatic regime at the time of their formation. One of the approaches discussed to this specific problem of landform genesis, and to the general problem of the present and past states of martian volatiles, is to attempt to constrain the distribution, amount, and history of available volatiles by using possible evidence of volatile participation expressed in the morphology of other related landforms (e.g., flow-ejecta blankets and landslides) coupled with physical models for landform genesis.

Pieri, D.↗
DOE OSTI2024

Quantifying Trapped Powder in Electron Beam Powder Bed Fusion

Abstract Electron beam powder bed fusion (PBF-EB) shows great potential for manufacturing complex parts including those with internal cavities for heat exchanger, manifold systems, or energy absorption purposes. PBF-EB allows for the manufacture of channel geometries without the need for support structures. Due to the nature of the powder spreading process, powder feedstock is often trapped in intentionally manufactured cavities. This trapped powder can often be difficult to remove and can disturb the intended flow of fluid through the cavity or damage downstream components in its use case. These trapped powder particles present a risk of contamination and component failure if not completely evacuated. Ti6Al4V is a choice material for aerospace applications due to its high strength to weight ratio and its composition as a nonferrous metal; however, in weight sensitive applications excess entrapped powders or powders loosely attached to the surface could cause undesirable weight increases. The inherent spreading process of PBF-EB is different than laser powder bed fusion (PBF-LB) in its operational temperature, sintering. In addition, PBF-EB is less commonly studied in literature compared to its PBF-LB counterpart, and as a result the complexity of the semi-sintered powder and its spreading behavior are not well understood. Prior work has investigated the difficulty in removing trapped powder from PBF-EB, but these studies do not address how to quantify the amount of trapped powder in the cavity. Thus, an accurate method to measure the amount of trapped powder in the cavity must be investigated. In this work, Ti6Al4V coupons were manufactured with horizontal and vertical cavities of three different sizes. Archimedes testing allows for the determination of density differences caused by porosity and trapped powders by measuring mass and volumetric dispersion. Computed tomography (CT) is well suited for segmenting the internal structure and features of a part and has been studied for applications including voids, porosity, and dross. Thus, CT was explored as a method for evaluating trapped powder content in this work. The volumetric representation of the segmentation of the reconstructed CT volume can vary greatly depending on the input filter and thresholding methods. In this study, four different types of segmentation approaches were evaluated to determine the best approach for segmenting the volume as compared to an operator labeled ground truth. The percentage density results from the Archimedes testing were compared to the volumetric percent density from the computed tomography approach. Differences in packing density between two different internal channel features were investigated. Overall, this work sought to validate the use of computed tomography for the detection of trapped powders and present a framework for volumetric segmentation.

Johnstone, Brian↗
NASA NTRS2002

Spin-Up Instability of a Levitated Molten Drop in MHD-Flow Transition to Turbulence

When an alternating magnetic field interacts with induced eddy currents in a conducting body, there will be a repulsive force between the body and the driving coil system generating the field. This repulsive force is the basis of electromagnetic levitation, which allows containerless processing of different materials. The eddy currents in the conducting body also generate Joule heating. Axial rotation of electromagnetically levitated objects is a common observation in levitation systems and often an undesirable side effect of such experiments on 1-g and -g. There have been recent efforts to use magnetic damping and suppress this tendency of body rotation. The first report of rotation in EML drops was attributed to a slight asymmetry of the shape and location of the levitation coils could change the axis and speed of rotation. Other theories of sample rotation include a frequency difference in the traveling electromagnetic waves and a phase difference in two different applied fields of the same frequency. All of these different mechanisms share the following characteristics: the torque is small, constant for constant field strength, and very weakly dependent on the sample's temperature and phase (solid or liquid). During experiments on the MSL-1 (First Microgravity Science Laboratory) mission of the Space Shuttle (STS-83 and STS-94, April and July 1997), a droplet of palladium-silicon alloy was electromagnetically levitated for viscosity measurements. For the non-deforming droplet, the resultant MHD flow inside the drop is inferred from motion of impurities on the surface. These observations indicate formation of a pair of co-rotating toroidal flow structures inside the spheroidal levitated drop that undergo secondary flow instabilities. As rise in the fluid temperature rises, the viscosity falls and the internal flow accelerates and becomes oscillatory; and beyond a point in the experiments, the surface impurities exhibit non-coherent chaotic motion signifying emergence of turbulence inside the drop. In this work, a background of these set of observations will be given followed by a presentation of our results on the digital particle tracking analysis that has been performed on a number of available videos. The analysis indicates that the levitated drop attains a constant rotational speed during the melting phase and formation of the co-rotating axi-symmetric laminar toroidal structures. However, the rate of axial rotation increases dramatically during the deformation of the toroidal structures anti their breakup into chaotic entities. This new data suggests an interaction between the flow inside the levitated molten drop and the driving coils in the experiments. Possible mechanisms for this interaction will be reviewed. The data will also be used to make an assessment of existing theories on droplet rotation.

Abedian, B.↗
NASA NTRS1986

Oblique impact: A process for providing meteorite samples of other planets

Cratering flow calculations for a series of oblique to normal impacts of silicate projectiles onto a silicate halfspace were carried out to determine whether the gas produced upon shock vaporizing both projectile and planetary material could entrain and accelerate surface rocks and thus provide a mechanism for propelling SNC meteorites from the Martian surface. The difficult constraints that the impact origin hypothesis for SNC meteorites has to satisfy are that these meteorites are lightly to moderately shocked and yet were accelerated to speeds in excess of the Martian escape velocity. Two dimensional finite difference calculations demonstrate that at highly probable impact velocities, vapor plume jets are produced at oblique impact angles of 25 deg to 60 deg and have speeds as great as 20 km/sec. These plumes flow nearly parallel to the planetary surface. It is shown that upon impact of projectiles having radii of 0.1 to 1 km, the resulting vapor jets have densities of 0.1 to 1 g/cu.cm. These jets can entrain Martian surface rocks and accelerate them to velocities 5 km/sec. It is suggested that this mechanism launches SNC meteorites to Earth.

Okeefe, J. D.↗
NASA NTRS1986

Oblique impact - A process for obtaining meteorite samples from other planets

Cratering flow calculations for a series of oblique to normal impacts of silicate projectiles onto a silicate halfspace were carried out to determine whether the gas produced upon shock vaporizing both projectile and planetary material could entrain and accelerate surface rocks and thus provide a mechanism for propelling SNC meteorites from the Martian surface. The difficult constraints that the impact origin hypothesis for SNC meteorities has to satisfy are that these meteorites are lightly to moderately shocked and yet were accelerated to speeds in excess of the Martian escape velocity. Two dimensional finite difference calculations demonstrate that at highly probable impact velocities, vapor plume jets are produced at oblique impact angles of 25 deg to 60 deg and have speeds as great as 20 km/sec. These plumes flow nearly parallel to the planetary surface. It is shown that upon impact of projectiles having radii of 0.1 to 1 km, the resulting vapor jets have densities of 0.1 to 1 g/cu cm. These jets can entrain Martian surface rocks and accelerate them to velocities 5 km/sec. It is suggested that this mechanism launches SNC meteorites to earth.

Okeefe, John D.↗
NASA NTRS2001

High-Flow PMR-Polymide Composites Developed With Mechanical Properties Comparable to Other High-Temperature Systems

PMR polyimides, in particular PMR-15, are well known for their excellent high-temperature stability and performance, and solvent resistance. However, the processing of these materials is limited, for the most part, to prepreg-based methods, such as compression or autoclave processing. These methods involve substantial amounts of hand labor, and as a result, manufacturing costs for components made from PMR polyimides can be high. In cost-sensitive applications, these high manufacturing costs can make the use of PMR polyimide-based components cost prohibitive. Lower cost manufacturing methods, such as resin transfer molding (RTM) and resin film infusion, have been demonstrated to reduce manufacturing costs by as much as 50 percent over prepreg-based methods. However, these processes are only amenable to materials with melt viscosities below 30 poise. Most PMR polyimides have melt viscosities on the order of 100 poise or higher. Recent efforts at the NASA Glenn Research Center have focused on chemical modifications to PMR polyimides to reduce their melt viscosity to the point where they could be processed by these low-cost manufacturing methods without adversely affecting their high-temperature properties and performance. These efforts have led to a new family of PMR polyimides that have melt viscosities significantly lower than that of PMR-15. Reductions in melt viscosity are brought about through the introduction of molecular twists in the polymer backbone. Carbon fiber (T650- 35) composites were prepared from one of these polyimides, designated PMR-Flex, by compression molding. The properties of these composites are presented below and compared with comparable composites made from PMR-15 and PETI-RTM, a new low-melt-viscosity polyimide.

Meador, Michael A.↗
NASA NTRSDate not supplied

Advances in Integrally Formed Metallic Structures

NASA Langley Research Center (LaRC) is applying flow forming technology to aerospace aluminum alloys for the manufacture of integrally stiffened cylinders that meet aircraft fuselage or launch vehicle specifications. High-strength 2xxx series alloys, in various temper/product form conditions, are being compared with medium-strength, very formable AA 6061 as the benchmark. Screening of candidate materials traditionally relies on empirical forming trials, but more recently on metrics derived from constant nominal strain rate tensile testing. In this work, the established hierarchy of formability metrics is adopted as the baseline; tensile area reduction, work hardening exponent, and modulus of resilience. The suite of metrics can be expanded based on phenomenological and mechanistic considerations of plastic flow instabilities to incorporate anisotropy ratio, rate of work hardening, and dynamic strain aging effects. Separate research thrusts at LaRC are aimed at formulating a protocol for scalable production of fully formed, defect-free components: 1) quantifying the extended set of formability metrics from constant and jump strain rate tensile tests with digital image correlation (DIC); 2) using statistically designed experiments on a vertical spin/flow forming facility (WF VUD-600®) to isolate the effect of convenient process variables, such as axial feed rate and thickness reduction; and 3) predicting the effect of feed ratio (roller translation relative to mandrel rotation speeds) on material response via process modeling using the DEFORM® simulation software. Current results will be discussed in terms of correlating intrinsic material properties with the bulk workability characteristics to successfully fabricate cylinders with complex cross-sections.

Aluminum↗
NASA NTRS1977

Heat exchanger-ingot casting/slicing process, phase 1: Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

A controlled growth, heat-flow and cool-down process is described that yielded silicon with a high degree of single crystallinity. Even when the seed melted out, very large grains formed. Solar cell samples made from cast material yielded conversion efficiency of over 9%. Representative characterizations of grown silicon demonstrated a dislocation density of less than 100/sq cm and a minority carrier diffusion length of 31 micron. The source of silicon carbide in silicon ingots was identified to be from graphite retainers in contact with silica crucibles. Higher growth rates were achieved with the use of a graphite plug at the bottom of the silica crucible.

Schmid, F.↗
NASA NTRS1979

Elevated temperature flow strength, creep resistance and diffusion welding characteristics of Ti-6Al-2Nb-1Ta-0.8Mo

A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo has been conducted. Two mill-processed forms of this alloy were examined. The forged material had been processed above the beta transus (approximately 1275 K) while the rolled form had been subjected to work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

Whittenberger, J. D.↗
NASA NTRS1991

Analysis of an initial lunar outpost life support system preliminary design

A preliminary design of a life-support system (LSS) was developed as part of an ongoing comprehensive trade study of advanced processor technologies and system architectures for an initial lunar outpost. The design is based on a mission scenario requiring intermittent occupation of a lunar-surface habitat by a crew of four. It incorporates physiochemical process technologies that were considered for Space Station Freedom. A system-level simulation model of the design was developed to obtain steady-state material balances for each LSS processor. The mass-flow rate predictions were used to obtain estimates of the LSS mass, volume, and power consumption by means of processor-sizing correlations that were extrapolated from Space Station Freedom processor designs. The results were used to analyze the impacts of varying crew size, mission duration, processor-operation strategy, and crew-cabin loads on the LSS mass, average power consumption, volume, periodic resupply mass, and waste-accumulation rates. The merits of the design were quantified relative to an open-loop LSS, and the implications of this assessment for future LSS research and technology development were identified.

Ballin, Mark G.↗
NASA NTRS1992

Design of a prototype Advanced Main Combustion Chamber for the Space Shuttle Main Engine

Development of a prototype advanced main combustion chamber is underway at NASA Marshall Space Flight Center. The Advanced Main Combustion Chamber (AMCC) project is being approached utilizing a 'concurrent engineering' concept where groups from materials, manufacturing, stress, quality, and design are involved from the initiation of the project. The AMCC design has been tailored to be compatible with the investment casting process. Jacket, inlet/outlet manifolds, inlet/outlet neck coolant flow splitters, support ribs, actuator lugs, and engine controller mounting bracket will all be a part of the one-piece AMCC casting. Casting of the AMCC in a one-piece configuration necessitated a method of forming a liner in its structural jacket. A method of vacuum plasma spraying the liner is being developed. In 1994, the AMCC will be hot-fired on the Technology Test Bed Space Shuttle Main Engine.

Lackey, J. D.↗
NASA NTRS2000

Turbulent Transition in Electromagnetically Levitated Drops

Electromagnetic levitation (EML) is an important tool in materials research. Because a sample can be processed without contact with a container, experiments may be performed on high temperature, highly reactive, and undercooled liquid metals. Many of these experiments are affected by fluid flow in the sample, driven by the electromagnetic positioning force. Despite the importance of convection in these experiments, the transition to turbulence is not well understood in this system. However, we have observed a transition from laminar to turbulent flow in EML droplets in the course of microgravity experiments in TEMPUS on the Space Shuttle (STS-94). The transition occurs repeatably and over a narrow range of conditions. These experimental observations are compared with two competing theories about the transition to turbulence. Also, the results of a particle tracking study of the instabilities leading up to the transition to turbulence are presented.

Hyers, Robert W.↗
NASA NTRS2001

Atomically Flat Surfaces Developed for Improved Semiconductor Devices

New wide bandgap semiconductor materials are being developed to meet the diverse high temperature, -power, and -frequency demands of the aerospace industry. Two of the most promising emerging materials are silicon carbide (SiC) for high-temperature and high power applications and gallium nitride (GaN) for high-frequency and optical (blue-light-emitting diodes and lasers) applications. This past year Glenn scientists implemented a NASA-patented crystal growth process for producing arrays of device-size mesas whose tops are atomically flat (i.e., step-free). It is expected that these mesas can be used for fabricating SiC and GaN devices with major improvements in performance and lifetime. The promising new SiC and GaN devices are fabricated in thin-crystal films (known as epi films) that are grown on commercial single-crystal SiC wafers. At this time, no commercial GaN wafers exist. Crystal defects, known as screw defects and micropipes, that are present in the commercial SiC wafers propagate into the epi films and degrade the performance and lifetime of subsequently fabricated devices. The new technology isolates the screw defects in a small percentage of small device-size mesas on the surface of commercial SiC wafers. This enables atomically flat surfaces to be grown on the remaining defect-free mesas. We believe that the atomically flat mesas can also be used to grow GaN epi films with a much lower defect density than in the GaN epi films currently being grown. Much improved devices are expected from these improved low-defect epi films. Surface-sensitive SiC devices such as Schottky diodes and field effect transistors should benefit from atomically flat substrates. Also, we believe that the atomically flat SiC surface will be an ideal surface on which to fabricate nanoscale sensors and devices. The process for achieving atomically flat surfaces is illustrated. The surface steps present on the "as-received" commercial SiC wafer is also illustrated. because of the small tilt angle between the crystal "basal" plane and the polished wafer surface. These steps are used in normal SiC epi film growth in a process known as stepflow growth to produce material for device fabrication. In the new process, the first step is to etch an array of mesas on the SiC wafer top surface. Then, epi film growth is carried out in the step flow fashion until all steps have grown themselves out of existence on each defect-free mesa. If the size of the mesas is sufficiently small (about 0.1 by 0.1 mm), then only a small percentage of the mesas will contain an undesired screw defect. Mesas with screw defects supply steps during the growth process, allowing a rough surface with unwanted hillocks to form on the mesa. The improvement in SiC epi surface morphology achievable with the new technology is shown. An atomic force microscope image of a typical SiC commercial epilayer surface is also shown. A similar image of an SiC atomically flat epi surface grown in a Glenn laboratory is given. With the current screw defect density of commercial wafers (about 5000 defects/cm2), the yield of atomically free 0.1 by 0.l mm mesas is expected to be about 90 percent. This is large enough for many types of electronic and optical devices. The implementation of this new technology was recently published in Applied Physics Letters. This work was initially carried out in-house under a Director's Discretionary Fund project and is currently being further developed under the Information Technology Base Program.

Powell, J. Anthony↗
NASA NTRS2006

Near Net Manufacturing Using Thin Gage Friction Stir Welding

Friction Stir Welding (FSW) and near net spin forming of FSW aluminumn blanks were investigated for large-scale pressure vessel applications. With a specific focus on very thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability, reliability and performance of pressure vessels larger than 10 ft. diameter.

Takeshita, Jennifer↗
NASA NTRS2008

Effect of Excess Lead and Bismuth Content on the Electrical Properties of High-Temperature Bismuth Scandium Lead Titanate Ceramics

Aeronautic and aerospace applications require piezoelectric materials that can operate at high temperatures. The air-breathing aeronautic engines can use piezoelectric actuators for active combustion control for fuel modulation to mitigate thermo-acoustic instabilities and/or gas flow control to improve efficiency. The principal challenge for the insertion of piezoelectric materials is their limitation for upper use temperature and this limitation is due low Curie temperature and increasing conductivity. We investigated processing, microstructure and property relationship of (1-x)BiScO3-(x)PbTiO3 (BS-PT) composition as a promising high temperature piezoelectric. The effect of excess Pb and Bi and their partitioning in grain boundaries were studied using impedance spectroscopy, ferroelectric, and piezoelectric measurement techniques. Excess Pb addition increased the grain boundary conduction and the grain boundary area (average grain size was 24.8 m, and 1.3 m for compositions with 0at.% and 5at.% excess Pb, respectively) resulting in ceramics with higher AC conductivity (tan d= 0.9 and 1.7 for 0at.% and 5at.% excess Pb at 350 C and at 10kHz) that were not resistive enough to pole. Excess Bi addition increased the resistivity (rho= 4.1x10(exp 10) Omega cm and 19.6 x10(exp 10) Omega.cm for compositions with 0at.% and 5at.% excess Bi, respectively), improved poling, and increased the piezoelectric coefficient from 137 to 197 pC/N for 5at.% excess Bi addition. In addition, loss tangent decreased more than one order of magnitude at elevated temperatures (greater than 300 C). For all compositions the activation energy of the conducting species was similar (approximately equal to 0.35-0.40 eV) and indicated electronic conduction.

Sehirlioglu, Alp↗