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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 343 records · Page 19

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Development of S-band antenna interface design, volume 1

The construction of an analytical thermal model of an S-band antenna in a typical Space Shuttle Orbiter installation is discussed. The selection and modeling of orbital and entry thermal environment inputs for the thermal analyses are discussed. The results of analyses for a variety of orbital thermal environments and entry initial conditions are given. Design and fabrication details of a thermal test fixture which physically approximates the Orbiter installation are discussed. The design and fabrication of two electrical test fixtures which electrically simulate the Orbiter surface shape and thermal protection system are discussed.

Kuhlman, E. A.↗

NASA NTRS1976

A parylene coating process for hybrid circuits

The parylene coating process developed during this program consists of (1) obtaining a hybrid cover with a hole in it, (2) sealing of the circuit with a hole in the cover, (3) parylene coating through the hole with the external leads protected from parylene by appropriate fixturing, and (4) sealing of the hole by soldering a pretinned kovar tab. Development of the above process required optimization of the parylene coater parameters to obtain a uniform consistent coating which could offer adequate protection to the circuits, fixture design for packages of various types, determination of the size of the deposition hole, and the amount of dimer charge per run, a process to hermetically seal the deposition holes and establishment of quality control techniques or acceptance criteria for the deposited film.

Source record↗

NASA NTRS1977

A hermetic sealing process for large irregularly shaped hybrid microcircuit enclosures

A system for sealing vacuum baked hybrids in a dry inert atmosphere using an overlapping spot resistance weld is described. A unique electrode configuration and fixturing that permits sealing of large and irregularly shaped gold plated Kovar packages to the hermeticity requirements of MIL-STD-883 was discussed. Metallurgical considerations and comparisons to laser sealing were made. Problems encountered during the development and optimization of the process were highlighted. Solutions to plating, fixturing, warpage, weld splatter and cracked bead problems are presented.

Stahler, M. R.↗

NASA NTRS1979

Slicing of Silicon into Sheet Material: Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project

Testing of low cost low suspension power slurry vehicles is presented. Cutting oils are unlikely to work, but a mineral oil with additives should be workable. Two different abrasives were tested. A cheaper silicon carbide from Norton gave excellent results except for excessive kerf loss: the particles were too big. An abrasive treated for lubricity showed no lubricity improvement in mineral oil vehicle. The bounce fixture was tested for the first time under constant cut rate conditions (rather than constant force). Although the cut was not completed before the blades broke, the blade lifetime of thin (100 micrometer) blades was 120 times the lifetime without the fixture. The large prototype saw completed a successful run, producing 90% cutting yield (849 wafers) at 20 wafers/cm. Although inexperience with large numbers of wafers caused cleaning breakage to reduce this yield to 74%, the yield was high enough that the concept of the large saw is proven workable.

Fleming, J. R.↗

NASA NTRS1978

Environmental exposure effects on composite materials for commercial aircraft

Activities reported include completion of the program design tasks, resolution of a high fiber volume problem and resumption of specimen fabrication, fixture fabrication, and progress on the analysis methodology and definition of the typical aircraft environment. Program design activities including test specimens, specimen holding fixtures, flap-track fairing tailcones, and ground exposure racks were completed. The problem experienced in obtaining acceptable fiber volume fraction results on two of the selected graphite epoxy material systems was resolved with an alteration to the bagging procedure called out in BAC 5562. The revised bagging procedure, involving lower numbers of bleeder plies, produces acceptable results. All required laminates for the contract have now been laid up and cured. Progress in the area of analysis methodology has been centered about definition of the environment that a commercial transport aircraft undergoes. The selected methodology is analagous to fatigue life assessment.

Hoffman, D. J.↗

NASA NTRS1981

Environmental testing under load

Inexpensive fixture applies compression loads to specimens exposed to environment. Fixture handles relatively large specimens suitable for postexposure analysis of physical, chemical, and mechanical properties.

Clark, R. K.↗

NASA NTRS1982

Retractor Tool for Brain Surgery

Proposed brain-surgery tool has an octogonal fixture for positioning latex tube over incision. Eight stainless-steel wires embedded in latex extend to hold positioning fixture. Another eight are also embedded in the latex. Concentric sleeves are successively inserted into expandable latex tube. The first sleeve is placed over a solid rod. Last sleeve is a stainless-steel tube 1 inch in diameter. It is overcoated with Teflon (or equivalent) material.

Helms, R.↗

NASA NTRS1981

Nickel hydrogen cell tests

Some parametric tests followed by cycling tests are described for the characterization of the service life of nickel hydrogen cells. Three cells were automatically cycled in simulated low Earth orbit in 35 minute discharge, 55 minute charge, with charging voltage limited, temperature compensated. The cells were mounted in a fixture that conducts heat to an aluminum baseplate. The baseplate in turn, is bounded in a temperature controlled bath to remove the heat from the mounted fixture. One cell was tested with a zircar separator, which failed after 2473 cyles. Two other cells were tested one with a zircar separator; the other with asbestos. More than 400 cycles were achieved.

Mueller, V. C.↗

NASA NTRS1983

Holder for Fragile Parts

Fixture with many springfingers holds irregularly-shaped parts. Gripping fixture has hundreds of springfingers, each applies minute force. Total force approximates hydrostatic pressure, resulting in well-distributed load that maintains firm grip without high stress concentrations. Applied to industrial robot manipulators, fixutre enhances ability to grasp delicate parts.

Holland, L. R.↗

NASA NTRS1983

Electrolytic Sharpening of Diode-Contact Whiskers

Phosphor bronze wire pointed without highly-toxic chemical reagents. Phosphor bronze wire to be pointed affixed to metal post held by fixture, such as pin vise. Fixture moved axially by micrometer allows precise control of position of end of wire with respect to surface of pointing solution. Solution consists of 4 weight percent sulfamic acid crystals in deionized water. Dissolution current adjusted via the autotransformer setting.

Green, G.↗

NASA NTRS1982

Strain rate characterization of unidirectional graphite/epoxy composite

For an investigation of problems of composites at high strain rates with dominant wave propagation effects, such as dynamically loaded composite jet engine blades, the longitudinal, transverse, and in-plane shear properties of unidirectional SP 288/AS graphite/epoxy were measured at various strain rates ranging from quasi-static to over 500/s. The test specimens were rings 10.16 cm in diameter, 2.54 cm long, 6 to 8 plies thick, and with fibers at 0, 90, and 10 deg off-axis. Quasi-static testing was conducted in a fixture which applies hydraulic pressure to the ring specimens, and dynamic testing was conducted by applying an internal pressure pulse through a liquid in a special fixture. Dynamic stress-strain curves are presented. For the 0-deg specimens, the modulus increases with strain up to 20 percent of the static value. The modulus and strength increase sharply in the 90-deg rings with strain rate reaching values two to three times the corresponding static rate.

Daniel, I. M.↗

NASA NTRS1981

Analysis of Barkhausen noise to assess shrink fit stresses

The possible application of Barkhausen Noise Analysis to assess shrink fit stresses in steel bushings was investigated. Ten specimens of four different size NAS steel bushings were used in experiments to determine the relationship between the Barkhausen signal amplitude and the hoop-stress in the bushings. This relationship was investigated for specimens which were loaded by a simple clamping fixture and specimens subjected to actual thermal interference fits. The results show that while the relationship of Barkhausen signal amplitude to hoop stress is predictable for specimens loaded by the simple clamping fixture, the relationship was less predictable for actual thermal fit bushings. The variation in results could possibly be due to variable levels of axial stress produced by the differential thermal expansion of the steel and aluminum.

Nondestructive testing↗

NASA NTRS1983

Design of low loss helix circuits for interference fitted and brazed circuits

The RF loss properties and thermal capability of brazed helix circuits and interference fitted circuits were evaluated. The objective was to produce design circuits with minimum RF loss and maximum heat transfer. These circuits were to be designed to operate at 10 kV and at 20 GHz using a gamma a approximately equal to 1.0. This represents a circuit diameter of only 0.75 millimeters. The fabrication of this size circuit and the 0.48 millimeter high support rods required considerable refinements in the assembly techniques and fixtures used on lower frequency circuits. The transition from the helices to the waveguide was designed and the circuits were matched from 20 to 40 GHz since the helix design is a broad band circuit and at a gamma a of 1.0 will operate over this band. The loss measurement was a transmission measurement and therefore had two such transitions. This resulting double-ended match required tuning elements to achieve the broad band match and external E-H tuners at each end to optimize the match for each frequency where the loss measurement was made. The test method used was a substitution method where the test fixture was replaced by a calibrated attenuator.

Jacquez, A.↗

NASA NTRS1986

Heat Bonding of Irradiated Ethylene Vinyl Acetate

Reliable method now available for joining parts of this difficult-tobond material. Heating fixture encircles ethylene vinyl acetate multiplesocket part, providing heat to it and to tubes inserted in it. Fixtures specially designed to match parts to be bonded. Tube-and-socket bonds made with this technique subjected to tensile tests. Bond strengths of 50 percent that of base material obtained consistently.

Slack, D. H.↗

NASA NTRS1983

Analysis of the stress state in an Iosipescu sheartest specimen

The state of stress in an Iosipescu shear test specimen is analyzed, utilizing a finite element computer program. The influence of test fixture configuration on this stress state is included. Variations of the standard specimen configuration, including notch depth, notch angle, and notch root radius are modeled. The purpose is to establish guidelines for a specimen geometry which will accommodate highly orthotropic materials while minimizing stress distribution nonuniformities. Materials ranging from isotropic to highly orthotropic are considered. An optimum specimen configuration is suggested, along with changes in the test fixture.

Walrath, D. E.↗

NASA NTRS1985

Design and Fabrication of the NASA Decoupler Pylon for the F-16 Aircraft, Addendum 2

The decoupler pylons which were originally designed and assembled with bushings in the pivot joints were retrofitted with roller bearings. This retrofit, the supporting analyses and the fixture tests of the modified pylons are reported in this document. The loads and stress analysis was directed toward the redesigned parts which were the pylon links and pins. The loads and stress analysis indicates that the pylons with the bearing installation have reduced capacity with respect to the bushing design. Fixture tests of the redesigned pylons were conducted in the GD/FW facility. Breakout friction tests and vibration tests were conducted. The tests show that the joint friction is approximately one-half the level with bearings as compared with the bushing installation. The vibration test data was used to tune the pylon mathematical simulation and this revised pylon simulation was used to recompute airplane modes of vibration. These computed modes of vibration were used in complete airplane symmetric and antisymmetric flutter and aeroservoelastic analyses.

Clayton, J. D.↗

NASA NTRS1987

Apparatus and method of capturing an orbiting spacecraft

Apparatus and a method of capturing an orbiting spacecraft by attaching a grapple fixture are discussed. A probe is inserted into an opening, such as a rocket nozzle, in the spacecraft until a stop on the prove mechanism contacts the spacecraft. A lever is actuated releasing a spring loaded rod which moves axially along the probe removing a covering sleeve to expose spring loaded toffle fingers which pivot open engaging the side of the opening. The probe is shortened and tensioned by turning a screw thread, pressing the fingers inside of the opening to compress the spacecraft between the toggle fingers and the stop. A grapple fixture attached to the probe, which is thus secured to the spacecraft, is engaged by appropriate retrieval means such as a remote manipulator arm.

Harwell, William D.↗

NASA NTRS1987

Further development of the losipescu shear test method

Recent activities by the present investigators to further develop the losipescu-shear-test method for use with composite materials are summarized. Finite-element analyses used to predict the stress states in the specimen are described, with particular emphasis on how they are influenced by the specific test-fixture configuration used. These same analytical tools were also used to predict the influence of specimen notch depth, notch angle, and notch-root radius. The result was a redesign of the original Wyoming version of the losipescu-shear-test fixture, and the establishment of guidelines for preparing specimens. These are discussed in some detail. Many references to available literature are included. An attempt has been made to put the work performed to date into perspective, to aid the potential user of the losipescu-shear-test method in establishing proper test procedures.

Adams, D. F.↗