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At least 199 records · Page 11

All sources NASA NTRS DOE OSTI

NASA NTRS1982

Ultrasonic input-output for transmitting and receiving longitudinal transducers coupled to same face of isotropic elastic plate

The quantitative understanding of ultrasonic nondestructive evaluation parameters such as the stress wave factor were studied. Ultrasonic input/output characteristics for an isotropic elastic plate with transmitting and receiving longitudinal transducers coupled to the same face were analyzed. The asymptotic normal stress is calculated for an isotropic elastic half space subjected to a uniform harmonic normal stress applied to a circular region at the surface. The radiated stress waves are traced within the plate by considering wave reflections at the top and bottom faces. The output voltage amplitude of the receiving transducer is estimated by considering only longitudinal waves. Agreement is found between the output voltage wave packet amplitudes and times of arrival due to multiple reflections of the longitudinal waves.

Williams, J. H., Jr.↗

NASA NTRS1982

Hot foil transducer skin friction sensor

The device utilizes foil transducers with only one edge exposed to the fluid flow. The surfaces are polished producing a foil transducer that does not generate turbulence while sufficiently thick to carry the required electrical current for high temperature fluid flow. The assembly utilizes a precut layered metal sandwich with attached electrodes eliminating a need for welding and individual sensor calibration.

Vranas, T.↗

NASA NTRS1985

Transducers For Heat Research

Series of transducers with seven different configurations enable measurement of forces and displacements in heart wall. New transducers small, cause minimal perturbation of heart function and attached and detached without causing excessive tissue damage. All units implanted or removed during single heartbeat, permitting rapid relocation for detail mapping.

Feldstein, C.↗

NASA NTRS1985

Multipurpose Photonic Transducers

Features include smallness and noise immunity. Photonic transducer is interferometer with two arms. Small relative axial motions of mirrors detected as shifts in interference pattern. Version measures temperature changes via differential expansion or contraction of stalks. New transducers smaller (typical size less than 1 cm) and coupled to monitoring equipment with optical fibers instead of wires. Well suited to biomedical instrumentation.

Du Fresne, E. R.↗

NASA NTRS1985

Fabricating Underwater Electroacoustic Transducers

Use of retainer ring instead of adhesives simplifies assembly and disassembly. Underwater electroacoustical transducer assembly uses precast silicone rubber compressed between ceramic crystal and metal container. Removable retainer ring holds assembly in place. Method provides proper stress loading, speed and ease of assembly, and way of removing transducer without damaging crystal.

Ferguson, R. L.↗

NASA NTRS1983

Ultrasonic transducer with a two-dimensional Gaussian field profile

A transducer is described which generates a two-dimensional Gaussian field by controlling both the position of multiple circular electrodes and the voltage applied to each electrode. The transducer is constructed by depositing concentric rings electrodes onto one flat surface of a circular piezoelectric crystal disk and attaching the rings to an impedance matching network which acts as a voltage divider. Geometrical inter-ring separations and electrical inter-ring impedances are designed to minimize the error between the generated acoustic field, modeled as a piecewise linear function, and the desired Gaussian distribution. Total mean squared error between the averaged far-field data and a Gaussian shape is less than two percent.

Claus, R. O.↗

NASA NTRS1985

Spring-Loaded Transducer Holder

Portable ultrasonic scanner moves transducer at constant pressure. Spring-loaded holder moves ultrasonic transducer over test sample at constant pressure. Setup used to determine rate of debond taking place in glued materials subjected to fatigue loading. Holder designed as portable field unit adapted to fatigue machine that transmits data while specimen tested.

Gardner, M. R.↗

NASA NTRS1986

Calibrating Pressure Transducers at Cryogenic Temperatures

To calibrate transducers immersed in cryogenic environment, sealed reciprocating bellows generates sinusoidal dynamic pressure. Transducer manifold assembly and bellows immersed in cryogenic environment to minimize gradients in controllable cryogenic temperature.

Gibbens, B. V.↗

NASA NTRS1985

An advanced solid state pressure transducer for high reliability SSME application

New methods to advance the state-of-the-art of pressure sensors for the Space Shuttle Main Engine were demonstrated. The results of the feasibility and breadboard demonstration phase and the current status of the research development prototype follow-on phase are presented. A technology breakthrough utilizing silicon piezoresistive technology was achieved in the first phase. A transducer design concept for the SSME application utilizes packaging materials with similar thermal coefficients of expansion and maintains the transducer seals primarily in compression. The silicon chip design will provide dual sensing outputs with laser trimmable integrated compensating electronics. The silicon resistor ion implant dose was customized for the SSME temperature requirement. A basic acoustic modeling software program was developed to evaluate the frequency response characteristics for the package design.

Johnson, R. L.↗

NASA NTRS1983

A thin film strain transducer

A device has been developed for the purpose of measuring longitudinal strain in thin polyethylene films. This paper describes the design, development, calibration, and application of this unique transducer in a variety of low temperature environments. This thin, ring-shaped device has a low effective modulus so as not to interfere with the strain that would naturally occur in a thin film. It has a standard 350 ohm impedance which is compatible with most available bridge balance, amplification, and telemetry instrumentation. This transducer has been successfully used for viscoelastic material characterization experiments in the laboratory, as well as in flight measurements of strain on the surface of scientific balloons during inflation, launch, ascent, and float.

Rand, J. L.↗

NASA NTRS1984

How to design and construct multielement ultrasonic transducers

The practical 'how to' design and construction of multielement ultrasonic transducers are described. First, design procedures based on direct calculations of the desired acoustic field are reviewed. Second, techniques for implementing these designs using piezoelectric active elements are discussed. Finally, optical and acoustic test methods for transducer calibration are indicated.

Burrier, R. A.↗

NASA NTRS1987

Pressure-Transducer Simulator

Simulation circuit operates under remote, automatic, or manual control to produce electrical outputs similar to pressure transducer. Specific circuit designed for simulations of Space Shuttle main engine. General circuit concept adaptable to other simulation and control systems involving several operating modes. Switches and amplifiers respond to external control signals and panel control settings to vary differential excitation of resistive bridge. Output voltage or passive terminal resistance made to equal pressure transducer in any of four operating modes.

Simon, Richard A.↗

NASA NTRS1986

Supplementary calibration test of the tip-aerodynamics- and acoustics-test pressure transducers

A calibration test is described that was performed to supplement the normal calibration of the 188 pressure transducers used in the Tip Aerodynamics and Acoustics Test. This calibration led to the identification of 15 transducers which had a slope change of greater than 7% from the initial calibration. The calibration procedure is described and the results presented. The effect of the slope changes on the pressure distributions are described, followed by a method to compensate for these changes.

Watts, M. E.↗

NASA NTRS1988

Calibrating Nonremovable Pressure Transducers

Report describes supplementary calibration procedure for pressure transducers. Method developed for transducers that cannot be removed without damage. Units calibrated en masse in large pressure chamber.

Watts, Michael E.↗

NASA NTRS1991

Rugged Direct-Current Transducer

Direct-current transducer withstands thermal and mechanical shocks. Operates from single, nominally 15-V power supply and nearly insensitive to both large variations in temperature and variations of as much as plus or minus 5 V in supply voltage. Its output voltage highly linear function of sensed current, with full-scale value of about 3 Vdc and offset of about 0.1 Vdc at 0 sensed current. Ruggedness of transducer due in large part to novel magnetic core, machined from solid block of nickel/iron high-permeability, low-hysteresis alloy.

Mclyman, W. T.↗

NASA NTRS1990

Acoustic transducer apparatus with reduced thermal conduction

A horn is described for transmitting sound from a transducer to a heated chamber containing an object which is levitated by acoustic energy while it is heated to a molten state, which minimizes heat transfer to thereby minimize heating of the transducer, minimize temperature variation in the chamber, and minimize loss of heat from the chamber. The forward portion of the horn, which is the portion closest to the chamber, has holes that reduce its cross-sectional area to minimize the conduction of heat along the length of the horn, with the entire front portion of the horn being rigid and having an even front face to efficiently transfer high frequency acoustic energy to fluid in the chamber. In one arrangement, the horn has numerous rows of holes extending perpendicular to the length of horn, with alternate rows extending perpendicular to one another to form a sinuous path for the conduction of heat along the length of the horn.

Lierke, Ernst G.↗

NASA NTRS1990

Photoelastic transducer for high-temperature applications

A design for a birefringence transducer for high-temperature applications is described. The spring element and the readout instrumentation are addressed. A pressure transducer based on the concept has been built and successfully tested at temperatures up to 600 C.

Redner, A. S.↗

NASA NTRS1992

Gel-Filled Holders For Ultrasonic Transducers

In new technique, ultrasonic transducer embedded in rubbery, castable, low-loss gel to enable transducer to "look" into surface of test object or human body at any desired angle. Composed of solution of water and ethylene glycol in collagen matrix. Provides total contact of water bath, also used on bodies or objects too large for water baths, even if moving. Also provides look angles of poly(methyl methacrylate) angle block with potential of reduced acoustic impedance and refraction. Custom-tailored to task at hand, and gel sufficiently inexpensive to be discarded upon completion. Easy to couple ultrasound in and out of gel, minimizing losses and artifacts of other types of standoffs employed in ultrasonic testing.

Companion, John A.↗