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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Plasma-Arc Torch For Welding Ducts In Place

Plasma-arc-welding torch redesigned, more suitable for applications in which moved in circular or other orbits about stationary cylindrical workpieces. Preserves elements of original design critical to performance and endurance, but modifies other elements to decrease overall size of torch. Electrode collet and collet nut installed and removed through hole in top; makes installation and removal easier.

Gangl, Kenneth J.↗
NASA NTRS1994

Plasma arc welding weld imaging

A welding torch for plasma arc welding apparatus has a transparent shield cup disposed about the constricting nozzle, the cup including a small outwardly extending polished lip. A guide tube extends externally of the torch and has a free end adjacent to the lip. First and second optical fiber bundle assemblies are supported within the guide tube. Light from a strobe light is transmitted along one of the assemblies to the free end and through the lip onto the weld site. A lens is positioned in the guide tube adjacent to the second assembly and focuses images of the weld site onto the end of the fiber bundle of the second assembly and these images are transmitted along the second assembly to a video camera so that the weld site may be viewed continuously for monitoring the welding process.

Rybicki, Daniel J.↗
NASA NTRS1973

Cyclic arc plasma tests of RSI materials using a preheater

The results of a test program are reported in which a preheater was used with an arc plasma stream to study the thermal response of samples of candidate reusable surface insulation materials for the space shuttle. The preheater simulated the shuttle temperature history during the first and last portions of the test cycle, which could not be simulated by the air arc plasma flow. Pre- and post-test data taken for each of the materials included magnified views, optical properties, and chemical analyses. The test results indicate that the mullite base samples experience higher surface temperatures than the other materials at heating rates greater than 225 kw/sq m. The ceramic fibrous mullite and silica coatings show noncatalytic wall behavior. Internal temperature response data for the materials are compared and correlated with analytical predictions.

Stewart, D. A.↗
NASA NTRS1993

Plasma arc welding repair of space flight hardware

A technique to weld repair the main combustion chamber of Space Shuttle Main Engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloy-Z, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloy-Z while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

Hoffman, David S.↗
DOE OSTI2019

Deoxidation of Ti Melt by Newly Developed Two-Step Plasma Arc Melting Process Using Hydrogen

A two-step plasma arc melting process, comprising a first step under Ar-30 pct H{sub 2} gas flow and the second step under Ar gas flow, has been newly developed for the deoxidation of Ti melts. The oxygen content after this process depended on the depth probed in the Ti melt. Decrease in the oxygen content from 1.5 to 0.7 mass pct in the surface region of the Ti melt occurred in the second step.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Superalloy material test in a plasma arc tunnel

Seven superalloy models were tested in a plasma arc tunnel at the peak heating condition existing on the space shuttle orbiter's lower surface during a low cross-range entry. The models were 3 x 3 in. flat surfaces, nominally 0.01 to 0.02 in. thick, and were held in a water-cooled wedge holder at a 60 deg angle of attack. Five test models were recycled 25 times for 10 min periods (two were recycled 50 times) in a Mach 4.6 test stream, with the model's leading edge temperature maintained at 2200 F (2000 F in one case).

Land, D. W.↗
NASA NTRS1994

UAH mathematical model of the variable polarity plasma ARC welding system calculation

Significant advantages of Variable Polarity Plasma Arc (VPPA) welding process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. A mathematical model is presented to analyze the VPPA welding process. Results of the mathematical model were compared with the experimental observation accomplished by the GDI team.

Hung, R. J.↗
NASA NTRS1999

Melting Efficiency During Plasma Arc Welding

A series of partial penetration Variable Polarity Plasma Arc welds were made at equal power but various combinations of current and voltage on 2219 aluminum. Arc Efficiency was measured calorimetrically and ranged between 48% and 66%. Melting efficiency depends on the weld pool shape. Increased current increases the melting efficiency as it increases the depth to width ratio of the weld pool. Higher currents are thought to raise arc pressure and depress the liquid at the bottom of the weld pool causing a more nearly two dimensional heat flow condition.

McClure, J.C.↗
DOE OSTI2017

Final Technical Report: Plasma Arc Gasification Based Rare Earth Element Recovery from Coal Fly Ash

Southern Research, as the primary awardee, with sub-awardees ArcSec Technologies, LLC (ArcSec) and Reaction Engineering International (REI) have investigated a plasma arc based thermal process intended to concentrate rare earth elements (REE) from coal fly ash. Successful demonstration of the technology would contribute to the effort for realizing a competitive, domestic REE value chain thereby reducing U.S. dependence on foreign supply, maintaining national security interests, and creating opportunities for economic growth. The originally proposed concept included two technology options – 1) a smelting process and 2) a smelting plus vaporization and condensation process. For both options, coal fly ash would be smelted in a plasma arc heated furnace under reducing conditions to separate ash into molten slag and reduced metal (primarily iron) phases. During smelting, it was expected that the REE would also be reduced to metals and partition mostly to the iron phase. During the first year of work, sample coal ash feedstocks were acquired and characterized, feasibility of the smelting process was evaluated in bench-scale experiments, and the vaporization/condensation process was investigated through equilibrium and CFD modeling studies. From the feedstock characterization, REE content for the coal ash samples obtained was measured to be in the range of 302 – 1219 ppm with average at 537 ppm. Though it was successfully demonstrated that ash could be separated into slag and metal phases, the bench-scale experiments were only marginally successful at collecting REE in the metal phase. Producing REE concentrates near the DOE goal of 2%, however, has not been achieved. From the modeling studies, the vaporization/condensation process was predicted to be effective for separating individual REE and producing enriched metal fractions with total REE content higher than 2%, provided the smelting process performed as intended. Supplemental smelting experiments and thermodynamic modeling studies, conducted during the second year of work, indicated a number of technical modifications that could lead to producing higher REE concentrates from coal ash. The strategy shifted to reducing as much of the ash oxides to metals as possible, leaving the REE more concentrated in the remaining slag. Results from later experiments based on the modified approach showed improvements in REE recovery and concentration levels in smelted products. SEM-EDS analyses on product specimens showed agglomerations of reduced metal REE crystals at much larger length-scales as compared to REE content in raw ash.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Microstructure and Mechanical Properties of Al-Mg-Sc-Zr Alloy Variable Polarity Plasma Arc Welding Joint

Al-Mg-Sc-Zr alloy plates were welded by variable polarity plasma arc welding (VPPAW) with Sc-containing filler wire. The microstructure and mechanical properties were investigated. Results show that the weld zone and heat-affected zone (HAZ) are narrow due to the high concentrated heat input of VPPAW. Primary Al{sub 3}(Sc,Zr) particles are nice nucleating sites for α-Al, which can significantly refine the grains of α-Al, helping the weld zone maintain an outstanding strength. The unmelted Al{sub 3}(Sc,Zr) precipitates of the base metal aggregated near the fusion boundary result in the formation of a fine equiaxed grains zone, which improves the bonding degree between the weld zone and the base metal. The Al{sub 3}(Sc,Zr) precipitates in the HAZ have excellent inhibition effect on recrystallization. According to the observed microhardness distribution and microstructure characteristics, the microstructure model of welded joint is obtained. The fractured position of welded joint locates in the weld zone. The tensile strength of the welded joint without reinforcing rib is 330 MPa. The welding coefficient reaches 74%.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Plasma arc welding repair of space flight hardware

Repair and refurbishment of flight and test hardware can extend the useful life of very expensive components. A technique to weld repair the main combustion chamber of space shuttle main engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloyZ, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloyZ while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

Hoffman, David S.↗
NASA NTRS1987

Morphology of zirconia particles exposed to D.C. arc plasma jet

Zirconia particles were sprayed into water with an arc plasma gun in order to determine the effect of various gun operating parameters on their morphology. The collected particles were examined by XRD and SEM techniques. A correlation was established between the content of spherical (molten) particles and the operating parameters by visual inspection and regression analysis. It was determined that the composition of the arc gas and the power input were the predominant parameters that affected the melting of zirconia particles.

Zaplatynsky, Isidor↗
DOE OSTI2019

A 6 MW/m 2 High Heat Flux Testing Facility of Irradiated Materials Using Infrared Plasma-Arc Lamps

Assessing the effect of neutron irradiation of plasma-facing materials has been challenging due to both the technical and radiological challenges involved. In an effort to address the radiological challenges, a facility was developed to conduct high heat flux testing (HHFT) of inherently small samples of neutron-irradiated materials. A new line-focus reflector was designed and fabricated at Oak Ridge National Laboratory for a plasma-arc lamp (PAL) to attain a source heat flux of 12 MW/m 2 . The new reflector was fabricated with two ports for monitoring specimen condition during HHFT. At the same operational conditions for PAL, the absorbed heat flux in tungsten was increased from 1.39 MW/m 2 with the uniform irradiance reflector to 5.12 MW/m 2 for the line-focus reflector. This fourfold increase in the heat flux, at the same PAL electrode lifetimes, enabled cost-effective facility operation for a high number of cyclic high heat flux tests. Specifically, the test section is confined to a hemispherical dome, and specimens are bolted directly to a water-cooled copper alloy rod. Temperature measurement in the PAL facility was a main challenge due to a limited line of sight. For the first time in a PAL facility operating at high heat fluxes, the specimen surface temperature was directly measured during HHFT with a pyrometer. Finally, the HHFT data, which were obtained in this upgraded PAL facility, demonstrated the facility readiness for irradiated materials.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗