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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 541 records · Page 30

All sources NASA NTRS DOE OSTI

NASA NTRS1976

A multi-modal solution for the transmission of sound in nonuniform ducts

The method of weighted residuals in the form of a modified Galerkin method with boundary residuals is developed for the study of the transmission of sound in nonuniform ducts carrying a steady compressible flow. In this formulation the steady flow is modeled as essentially one-dimensional but with a kinematic modification to force tangency of the flow at the duct walls. Good agreement has been obtained with known results for transmission and reflection coefficients in hard walled ducts up to near sonic velocities. In ducts with acoustically compliant boundaries good comparisons have been more difficult to achieve except at low Mach numbers. The problem of transmission in a straight, acoustically treated duct with a uniform flow has been formulated and the Galerkin method used with basis functions derived from the case when flow is absent. Results indicate that favorable comparisons with exact computations can be obtained if care is taken in choosing the basis functions.

Eversman, W.↗

NASA NTRS1976

Liquid cooled brassiere and method of diagnosing malignant tumors therewith

A device for enhancing the detection of malignant tissue in the breasts of a woman was described. A brassiere-like garment which is fitted with a pair of liquid-perfused cooling panels which completely and compliantly cover the breasts and upper torso was studied. The garment is connected by plastic tubing to a liquid cooling system comprising a fluid pump, a solenoid control valve for controlling the flow of fluid to either the cooling unit or the heating unit, a fluid reservoir, a temperature sensor in the reservoir, and a restrictor valve to control the pressure in the garment inlet cooling line.

Elkins, W.↗

NASA NTRS1978

Friction and wear of several compressor gas-path seal movements

Rub interaction experiments were conducted on a series of sintered and plasma sprayed compressor gas path seal materials in contact with Ti-6Al-4V blade tip and knife edge rotors. The most rub tolerant materials investigated were sintered Nichrome and plasma sprayed nickel 25 percent graphite. The effectiveness of providing a compliant substrate for dense seal material coatings was also demonstrated. In general, it was observed that rotor wear and high frictional energy generation rates accompanied smearing or surface densification of the materials investigated. The onset of smearing was sensitive to rub interaction parameters and seal geometry. Two complementary models were proposed to account for the smearing trends. One is based on thermal effects, the other on particulate escape effects. They were shown to be consistent with the experimental evidence at hand, and together they predict that smearing, with the onset of high energy rub conditions, is favored when incursion rates (radial motion) are low, incursion depths are high, the seal geometry is of a knife-edge character, and the seal particle size is small.

Bill, R. C.↗

NASA NTRS1979

Fastener for easy installation and removal of tiles

Mating strips, one with metal hooks and one with metal loops, allow convenient mounting and removal on many kinds of modules. Principle is adaptable to applications where shear-resistant, compliants, removable fastening is needed in hard-to-reach places, especially when attached part is lightly loaded or fragile.

Maletz, L. H.↗

NASA NTRS1979

Design, fabrication and spin testing of ceramic blade metal disk attachment

A ceramic turbine blade-metal disk attachment was designed for small, non man-rated turbine engine applications. The selected design consisted of a hot pressed silicon nitride blade having a skewed dovetail attachment with a compliant interlayer between the disk and the blade. Two-dimensional and three-dimensional analyses predicted that life goals could be achieved, considering both NDE limitations and crack growth rates for the ceramic material. Twenty ceramic blades were fabricated to closely-held manufacturing tolerances. New fracture mechanics data at elevated temperature are presented.

Calvert, G.↗

NASA NTRS1978

Ceramic blade attachments

Studies under way on two concepts for producing a turbine rotor with ceramic blades and superalloy disks are discussed. One concept employs hot-pressed silicon nitride blades and a compliant interlayer at the blade root end fitting whereas the second concept relies on a superplastic plastic forging technique to attach ceramic blades to the metal disk. This latter concept has been hot spin tested at 2250 F and 45,000 RPM for 50 hours in a vacuum spin pit. The fully bladed (30 blades) rotor survived this major test.

Calvert, G. S.↗

NASA NTRS1979

Engineering risk reduction in satellite programs

Methods developed in planning and executing system safety engineering programs for Lockheed satellite integration contracts are presented. These procedures establish the applicable safety design criteria, document design compliance and assess the residual risks where non-compliant design is proposed, and provide for hazard analysis of system level test, handling and launch preparations. Operations hazard analysis identifies product protection and product liability hazards prior to the preparation of operational procedures and provides safety requirements for inclusion in them. The method developed for documenting all residual hazards for the attention of program management assures an acceptable minimum level of risk prior to program deployment. The results are significant for persons responsible for managing or engineering the deployment and production of complex high cost equipment under current product liability law and cost/time constraints, have a responsibility to minimize the possibility of an accident, and should have documentation to provide a defense in a product liability suit.

Dean, E. S., Jr.↗

NASA NTRS1979

Gas path seal

A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.↗

NASA NTRS1980

High temperature self-lubricating coatings for air lubricated foil bearings for the automotive gas turbine engine

coating combinations were developed for compliant surface bearings and journals to be used in an automotive gas turbine engine. The coatings were able to withstand the sliding start/stops during rotor liftoff and touchdown and occasional short time, high speed rubs under representative loading of the engine. Some dozen coating variations of CdO-graphite, Cr2O3 (by sputtering) and CaF2 (plasma sprayed) were identified. The coatings were optimized and they were examined for stoichiometry, metallurgical condition, and adhesion. Sputtered Cr2O3 was most adherent when optimum parameters were used and it was applied on an annealed (soft) substrate. Metallic binders and interlayers were used to improve the ductility and the adherence.

Bhushan, B.↗

NASA NTRS1982

Heat Lamps Solder Solar Array Quickly

Interconnection tabs in a nine-solar-cell array have been soldered simultaneously with radiant heat. Cells and tabs are held in position for soldering by sandwiching them between compliant silicone-rubber vacuum platen and transparent polyimide sealing membrane. Heat lamps warm cells, producing smooth, flat solder joints of high quality.

Coyle, P. J.↗

NASA NTRS1982

Air Bag Applies Uniform Bonding Pressure

Air-bag box applies constant uniform pressure to tiles and other objects undergoing adhesive bonding. Box is basically a compliant clamp with adjustable force and position. Can be used on irregular surfaces as well as on flat ones. Pressurized air is fed to bag through a tube so that it expands, filling the box and pressing against work. Bag adopts a contour that accommodates surface under open side of box.

Gillespie, C. A.↗

NASA NTRS1976

Evaluation of advanced microelectronic fluxless solder-bump contacts for hybrid microcircuits

Technology for interconnecting monolithic integrated circuit chips with other components is investigated. The advantages and disadvantages of the current flip-chip approach as compared to other interconnection methods are outlined. A fluxless solder-bump contact technology is evaluated. Multiple solder-bump contacts were formed on silicon integrated circuit chips. The solder-bumps, comprised of a rigid nickel under layer and a compliant solder overlayer, were electroformed onto gold device pads with the aid of thick dry film photomasks. Different solder alloys and the use of conductive epoxy for bonding were explored. Fluxless solder-bump bond quality and reliability were evaluated by measuring the effects of centrifuge, thermal cycling, and high temperature storage on bond visual characteristics, bond electrical continuity, and bond shear tests. The applicability and suitability of this technology for hybrid microelectronic packaging is discussed.

Mandal, R. P.↗

NASA NTRS1980

Dynamic characteristics of a high-speed rotor with radial and axial foil-bearing supports

An asymmetric rotor (19N; 4.3 lb), supported radially and axially by compliant bearings is subjected to severe excitation by rotating unbalance in the 'pitching' mode at speeds to 50,000 rpm. The resilient, air-lubricated bearings provide very effective damping, so that regions of resonance and instability can be traversed with amplitudes and limit-trajectories within acceptable bounds. A novel journal bearing is introduced, in which a resilient support is furnished by the outer turn of the coiled foil-element bent to form an open polygon. The experimental apparatus and procedure are described, and the response of the rotor and flexible support system are documented by oscilloscope records of motion.

Licht, L.↗

NASA NTRS1980

Hybrid position/force control of manipulators

A new conceptually simple approach to controlling compliant motions of a robot manipulator is presented. The 'hybrid' technique described combines force and torque information with positional data to satisfy simultaneous position and force trajectory constraints specified in a convenient task related coordinate system. Analysis, simulation, and experiments are used to evaluate the controller's ability to execute trajectories using feedback from a force sensing wrist and from position sensors found in the manipulator joints. The results show that the method achieves stable, accurate control of force and position trajectories for a variety of test conditions.

Raibert, M. H.↗

NASA NTRS1980

Viscous flow drag reduction; Symposium, Dallas, Tex., November 7, 8, 1979, Technical Papers

The symposium focused on laminar boundary layers, boundary layer stability analysis of a natural laminar flow glove on the F-111 TACT aircraft, drag reduction of an oscillating flat plate with an interface film, electromagnetic precipitation and ducting of particles in turbulent boundary layers, large eddy breakup scheme for turbulent viscous drag reduction, blowing and suction, polymer additives, and compliant surfaces. Topics included influence of environment in laminar boundary layer control, generation rate of turbulent patches in the laminar boundary layer of a submersible, drag reduction of small amplitude rigid surface waves, and hydrodynamic drag and surface deformations generated by liquid flows over flexible surfaces.

Hough, G. R.↗

NASA NTRS1981

Low thermal conductance rigidizer for reducing torsional oscillations in cryogenic Dewars

A rigidizer, which provides greater rigidity against torsional oscillations, is highly resistant to radial motions, and has low thermal conductivity, has been developed to decrease vibrational levels affecting infrared detectors operated in cryostats (e.g., HD-3L Dewar) in aircraft such as NASA's Kuiper Airborne Observatory. The rigidizer is composed of two triangular elements and an intermediate support structure which joins them at the centers of their sides. The reentrant design provides a long heat path, while the triangular truss structure provides high rigidity in the horizontal plane. The structure is relatively compliant in the vertical direction, a desirable feature since the internal structure of the Dewar contracts as it cools. Rigidity in the vertical direction is provided by the neck tube. The support structure is quite compact. Several variants of the rigidizer have been fabricated, using flat sheets of G-10 fiberglass epoxy in thicknesses between 0.75-1.5 mm for the upper and lower truss assemblies, and either G-10 or stainless steel for the intermediate structure.

Harper, D. A.↗

NASA NTRS1981

Composite seal for turbomachinery

A gas path seal suitable for use with a turbine engine or compressor is provided. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor blades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.↗

NASA NTRS1984

Membrane Switches Check Seal Pressure

Array of flexible membrane switches used to indicate closure of seal. Switch membrane responds to pressure exerted by rigid surface on compliant sealing medium and provides switch contacts monitored electronically. Membrane switches connected in series and placed under seal. When all switches are closed lamp or LED lights up, indicating requisite seal pressure has been realized at all switch positions. Principle used to ensure integrity of seals on refrigerator and oven doors, weatherstripping, hatches, spacecraft, airplanes, and submarines.

Hodgetts, P. J.↗