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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1957

Preliminary metallographic studies of ball fatigue under rolling-contact conditions

The metallurgical results produced on balls tested in the rolling-contact fatigue spin rig were studied by metallographic examination. Origin and progression of fatigue failures were observed. These evaluations were made on SAE 52100 and AISI M-1 balls fatigue tested at room temperature (80 F) and 200 to 250 F. Most failures originated subsurface in shear; inclusions, structure changes, and directionalism adversely affected ball fatigue life. Structures in the maximum-shear-stress region of the balls of both materials were stable at room temperature and unstable at 200 to 250 F. Failures were of the same type as those found in full-scale bearings.

SURFACES, CONTACT - ROLLING↗
NASA NTRS1957

Stress-life relation of the rolling-contact fatigue spin rig

The rolling-contact fatigue spin rig was used to test groups of SAE 52100 9.16-inch-diameter balls lubricated with a mineral oil at 600,000-, 675,000-, and 750,000-psi maximum Hertz stress. Cylinders of AISI M-1 vacuum and commercial melts and MV-1 (AISI M-50) were used as race specimens. Stress-life exponents produced agree closely with values accepted in industry. The type of failure obtained in the spin rig was similar to the subsurface fatigue spells found in bearings.

SURFACES, CONTACT - ROLLING↗
NASA NTRS1957

Effect of Fiber Orientation on Ball Failures Under Rolling-contact Conditions

The rolling-contact fatigue spin rig was used to test bails of a bearing steel at maximum Hertz stresses of 600,000 to 750,000 psi. The effect of fiber orientation was observed with the ball track restricted to passing directly over the poles, coincident with the equator, or randomly around the ball. The polar areas were found to be weaker in fatigue than the nonpolar areas. This resulted in a much greater portion of the failures occurring in the polar areas than would be expected from a homogeneous material. The early failures are discussed.

MATERIALS, PROPERTIES - FATIGUE↗
NASA NTRS2020

On Orbit Flight Testing of the Roll-Out Solar Array

The Roll-Out Solar Array (ROSA) is an innovative, lightweight solar array with a flexible substrate that makes use of the stored strain energy in its composite structural members to provide deployment without the use of motors while still packaging efficiently. The ROSA flight experiment was launched to the International Space Station (ISS)on June 3rd, 2017 as a part of the eleventh SpaceX commercial resupply mission. After two weeks of storage, ROSA was extracted from the Dragon spacecraft, deployed, and put through a week of tests to verify its structural characteristics as well as the performance of photovoltaics. The structural dynamics experiments included active excitation of out-of-plane bending modes, and a study of the thermal-structural interaction of the structure during day-night transitions. Data was gathered from a small number of accelerometers located at key points on the solar array and from cameras observing numerous photogrammetry targets spread out over the structure and the photovoltaic blanket. The goal in this effort was to better understand the performance of ROSA and to improve modeling efforts for future designs of similar solar arrays. Of particular interest are the first few system modes and mode shapes of the array, the amount of structural damping present, and degree of structural-thermal interaction seen during eclipse exit.

ROSA↗
DOE OSTI2018

Irreversibility in Rolled Tantalum

We investigated the magnetic and thermodynamic properties of rolled tantalum in superconducting state. The magnetization shows a crossover from type I to type II superconductivity as the magnetic field increases beyond the thermodynamic critical field. In both regimes, the sample shows a substantial irreversibility of the magnetization which we attribute to the pinning of the entities that characterize the intermediate and mixed states. Magnetic relaxation data taken in the intermediate state shows an important contribution of the quantum tunnelling below 3.7 K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Reel-to-Reel Heat Treatment, Microstructure, and Superconducting Properties of Jelly-Roll Nb{sub 3}Al Superconducting Wire

In this work, we utilized the jelly-roll method to make a single-filament Nb{sub 3}Al precursor long wire, combining with a homemade reel-to-reel rapid heating and quenching (RHQ) equipment, and consequently the high-performance Nb{sub 3}Al superconducting wires had been prepared. By investigating the heating current and wire moving speed, the optimized RHQ heat treatment conditions of this Nb{sub 3}Al wire were obtained. The results suggest that the T{sub c} for the Nb{sub 3}Al superconducting wire is up to 17.4 K and the non-Cu critical current density (non-Cu J{sub c}) reaches 1238 A/mm{sup 2} at 4.2 K and 12 T, which indicates the bcc-phase Nb–Al supersaturated solid solution has already been generated. Considering the Nb{sub 3}Al precursor wire with a large thickness of Al layer, about 690 nm, such high J{sub c} is quite unexpected. The SEM analysis presents that there is still some unreacted Nb and Nb{sub 2}Al phase in the superconducting wire, which may result from the inhomogeneity of Nb and Al foils. This work implies the Nb{sub 3}Al superconducting wire is promising to the application of high-field superconducting magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗