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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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A low friction, two-component bearing comprised of a pair of ball-bearing races for transmitting rotary motion and an inner series of ball bearing assemblies for transmitting axial motion is described and should be useful in mechanisms such as stress-strain testing machines.
Components for a high-reliability system such as the Telstar project are obtained by: (a) design of the component for the required environment, (b) careful control of manufacturing processes, (c) elimination of potential early failures by screening tests, and (d) selection of the most stable components. For passive components, these methods could be applied by using design parameters, suppliers and screening techniques established in the earlier submarine cable program, with consideration being given to the additional effects of the satellite launch and orbit environments. Semiconductor component designs were selected by qualification tests using accelerated electrical and environmental stress conditions. Screening tests were applied to eliminate early failures, and resulting components were aged from two to six months before selection for the satellite. The recognition of the effect of ionizing radiation on transistors caused the addition of a radiation qualification test, or a screening to assure selection of the least sensitive devices. Tests have shown this screening to be effective for the radiation intensity expected. Experience with the passive components, and evaluation of the accelerated test results and aging data of the semiconductor devices, indicate that the reliability objective was obtained.
Palmgren-Miner, Manson, Fuller, and Valluri methods of predicting fatigue life in spectrum loading
A program has been initiated to develop a material with superior properties at elevated temperatures for utilization in turbine blade applications. A nickel-base superalloy can provide the necessary high temperature strength by using the maximum capability of the three available strengthening mechanisms - intermetallic gamma prime precipitation (Ni3Al), solid solution strengthening with refractory and precious metals, and stable carbide formations through the addition of strong carbide forming elements. A stress rupture test at 2000 deg F and 15,000 psi was formulated to approximate the desired properties. By adding varying amounts of refractory metals (Mo, W and Ta) it was possible to statistically analyze the effects of each in a basic superalloy composition containing fixed amounts of Co, Cr, C, B, Sr, and Ni at three separate levels of AL and Ta. Metallographic analysis correlated with the mechanical properties of the alloys; those with few strengthening phases were weak and ductile and those with excessive amounts of intermetallic phases present in undesirable morphologies were brittle.
Creep tests and stress levels in determining mechanical behavior of polycrystalline nonmetallic materials at elevated temperatures
Materials research - diffusion bonding methods, stress corrosion tests, nondestructive testing, material designs for electronic equipment, and nonmetallic material development.
Constant-amplitude reverse bend stress fatigue testing device for extreme high vacuum, testing aluminum
Stress corrosion tests of titanium alloys in distilled and aqueous salt solutions at ambient temperatures employing single edge notched specimens
Stress corrosion tests of heat treated austenitic stainless steels
Hydrogen effects on ELI Ti-Al-Sn alloy, conducting tensile, fretting and abrasion tests on stressed and thermal cycled specimens
Stress corrosion tests of titanium alloys in fluids
Stress corrosion tests of AISI - H-11 alloy steel plated with nickel-cadmium coating
Tensile and stress rupture tests of cobalt alloy HS-31 in as-extruded and heat-treated states
Hydrogen effects on ELI Ti-Al-Sn alloy, conducting tensile, fretting and abrasion tests on stressed and thermal cycled specimens
Energy storage in creep deformed graphite from stress reduction tests, discussing negative creep, test procedures and results
Tensile and stress rupture tests of Co base alloy bars extruded from prealloyed powders made by Ar gas atomization
The activated diffusion brazing process was developed for attaching TD-NiCr and U700 finned airfoil shells to matching Rene 80 struts obstructing the finned cooling passageways. Creep forming the finned shells to struts in combination with precise preplacement of brazing alloy resulted in consistently sound joints, free of cooling passageway clogging. Extensive tensile and stress rupture testing of several joint orientation at several temperatures provided a critical assessment of joint integrity of both material combinations. Trial blades of each material combination were fabricated followed by destructive metallographic examination which verified high joint integrity.
Consolidated powders of four nickel-base superalloys were studied for potential application as compressor and turbine discs in jet engines. All of the alloys were based on the Rene' 95 chemistry. Three of these had variations in carbon and A12O3 contents, and the fourth alloy was chemically modified to a higher volume fraction. The A12O3 was added by preoxidation of the powders prior to extrusion. Various levels of four experimental factors (1) alloy composition, (2) grain size, (3) thermomechanical processing, and (4) room temperature deformation plus final age were evaluated by tensile and stress rupture testing at 1200 F. Various levels of the four factors were assumed in order to construct the statistically-designed experiment, but the actual levels investigated were established in preliminary studies that preceded the statistical process development study.