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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Graphite polyimide fabrication research for supersonic cruise aircraft

Advanced fabrication processes and adhesive bonding methods have been developed for the fabrication of full scale fiberglass-polyimide honeycomb stiffened HTS-1 graphite/PMR-15 polyimide panels that meet the design criteria for an upper wing panel of the NASA YF-12 aircraft. Detailed manufacturing, bonding, and autoclave cure procedures are presented. Nondestructive test methods including pulse echo and through-transmission ultrasonic C-scan and laser holography were developed to detect flaws in components and the completed panels. Panels were tested in shear at room temperature and 533 K (500 F) following a variety of thermal exposures to obtain load, deflection and failure analysis data.

Freeman, W. T., Jr.↗
NASA NTRS1981

Holographic flow visualization of time-varying shock waves

Rapid-double-exposure, diffuse-illumination holography is evaluated analytically and experimentally as a flow visualization method for time-varying shock waves. Conditions are determined that minimize the distance (localization error) between the surface or curve of interference-fringe localization and the shock surface. Treated specifically are the cases of shock waves in a transonic compressor rotor for which there is laser anemometer data for comparison and shock waves in a flutter cascade.

Decker, A. J.↗
NASA NTRS1979

Investigations on transparent liquid-miscibility gap systems

Sedimentation and phase separation is a well known occurrence in monotectic or miscibility gap alloys. Previous investigations indicate that it may be possible to prepare such alloys in a low-gravity space environment but recent experiments indicate that there may be nongravity dependent phase separation processes which can hinder the formation of such alloys. Such phase separation processes are studied using transparent liquid systems and holography. By reconstructing holograms into a commercial-particle-analysis system, real time computer analysis can be performed on emulsions with diameters in the range of 5 micrometers or greater. Thus dynamic effects associated with particle migration and coalescence can be studied. Characterization studies on two selected immiscible systems including an accurate determination of phase diagrams, surface and interfacial tension measurements, surface excess and wetting behavior near critical solution temperatures completed.

Lacy, L. L.↗
NASA NTRS1982

Holographic interferometry and tomography at Ames Research Center

A YAG laser holographic interferometer system and reconstruction laboratory for the Ames 2- by 2-Foot Transonic Wind Tunnel are discussed. This system provides dual plate and double pulse holography for quantitative and qualitative measurements, respectively. Interferometric measurements of two-dimensional airfoils and three-dimensional bodies of revolution for a tomography feasibility study were made. The two-dimensional work included supercritical airfoils, an oscillating airfoil undergoing dynamic stall, and a circulation control airfoil. The tomography experiments centered around hemispherical nose and tangent ogive models. In addition, the tomography work covered the development of a Fourier transform code for the retrieval of the three dimensional density distributions from the interferograms.

Lee, G.↗
NASA NTRS1982

The application of nonintrusive optical methods for physical measurements in combustion

Laser optical diagnostic techniques have proven to be effective for making physical measurements in hostile combustion environments. Two major and complementary approaches have been applied; namely, single event imaging and multi-signal detection methods. Single event imaging methods (e.g., pulsed laser holography) can provide the essentially instantaneous observation of physical events, e.g., fuel atomization, droplet breakup, particle and surface combustion, condensed phase formation, and flow field visualization. Multi-signal detection methods, which involve the processing of signals produced by the light scattered from the interaction of particles and/or droplets with an incident coherent ray, can provide information on flow velocity, turbulence, fluid shear stresses, and particle/droplet size and velocity. Recent results using both approaches are presented.

Wuerer, J. E.↗
NASA NTRS1982

Three-dimensional shock structure in a transonic flutter cascade

Rapid double-pulse holography was employed to obtain detailed, two-dimensional images of the shock forming during simulated flutter in a transonic flowfield. The experiment comprised a linear cascade of airfoils externally oscillated in torsion and viewed tangentially at the shock surface. Three biconvex airfoils were subjected to harmonic pitching motion about the midchord axis at a frequency of 0.53 while immersed in a Mach 0.81 flow. Failure to produce observable shocks led to use of choked flow with a Mach number near one, of which 50 holograms were taken. The images revealed a narrow shock surface with a spanwise variation in the shock properties. The method is concluded to be useful for examining transonic flowfield shocks in the presence of airfoil flutter.

Boldman, D. R.↗
NASA NTRS1984

Eddy-Current Inspection of Narrow Metal Tubes

Inspection technique for narrow-bore metal tubing involves use of small internal eddy-current probe. Probe consists of thin copper wire wrapped on bobbin. Probe small enough to pass through bends in tube being measured. Technique useful for strain measurements where operating conditions or inaccessibility prevent use of such conventional methods as X-ray diffraction, electrical-resistance measurements, strain gages, or holography.

Ambrose, H. H.↗
NASA NTRS1981

Holographic interferometry technique for rotary wing aerodynamics and noise

The concepts of holography and holographic interferometry, as applied to the visualization and measurement of the three dimensional flow field near a rotor tip, are previewed, and initial experimental results of investigations of local shock structures and tip vortices behind the blade are presented. An additional method to visualize the flow in a three dimensional manner is demonstrated, and finally, a method to quantitatively measure the three dimensional flow, which will provide the necessary information to help improve helicopter performance and reduce noise, is introduced.

Kittleson, J. K.↗
NASA NTRS1983

Experimental methods for identifying failure mechanisms

Experimental methods for identifying failure mechanisms in fibrous composites are studied. Methods to identify failure in composite materials includes interferometry, holography, fractography and ultrasonics.

Daniel, I. M.↗
NASA NTRS1983

Low-cost single-crystal turbine blades, volume 1

The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

Strangman, T. E.↗
NASA NTRS1984

Measurements in liquid fuel sprays

Techniques for studying the events directly preceding combustion in the liquid fuel sprays are being used to provide information as a function of space and time on droplet size, shape, number density, position, angle of flight and velocity. Spray chambers were designed and constructed for: (1) air-assist liquid fuel research sprays; (2) high pressure and temperature chamber for pulsed diesel fuel sprays; and (3) coal-water slurry sprays. Recent results utilizing photography, cinematography, and calibration of the Malvern particle sizer are reported. Systems for simultaneous measurement of velocity and particle size distributions using laser Doppler anemometry interferometry and the application of holography in liquid fuel sprays are being calibrated.

Chigier, N.↗
NASA NTRS1984

Separation processes during binary monotectic alloy production

Observation of microgravity solidification processes indicates that outside of sedimentation, at least two other important effects can separate the phases: critical-point wetting and spreading; and thermal migration of second-phase droplets due to interfacial tension gradients. It is difficult to study these surface tension effects while in a unit gravity field. In order to investigate the processes occurring over a temperature range, i.e., between a consolute point and the monotectic temperature, it is necessary to use a low-gravity environment. The MSFC drop tube (and tower), the ballistic trajectory KC-135 airplane, and the Space Shuttle are ideal facilities to aid formation and testing of hypotheses. Much of the early work in this area focuses on transparent materials so that process dynamics may be studied by optical techniques such as photography for viewing macro-processes; holography for studying diffusional growth; spinodal decomposition and coalescence; ellipsometry for surface wetting and spreading effects; and interferometry and spectroscopy for small-scale spatial resolution of concentration profiles.

Frazier, D. O.↗
NASA NTRS1984

Holographic aids for internal combustion engine flow studies

Worldwide interest in improving the fuel efficiency of internal combustion (I.C.) engines has sparked research efforts designed to learn more about the flow processes of these engines. The flow fields must be understood prior to fuel injection in order to design efficient valves, piston geometries, and fuel injectors. Knowledge of the flow field is also necessary to determine the heat transfer to combustion chamber surfaces. Computational codes can predict velocity and turbulence patterns, but experimental verification is mandatory to justify their basic assumptions. Due to their nonintrusive nature, optical methods are ideally suited to provide the necessary velocity verification data. Optical sytems such as Schlieren photography, laser velocimetry, and illuminated particle visualization are used in I.C. engines, and now their versatility is improved by employing holography. These holographically enhanced optical techniques are described with emphasis on their applications in I.C. engines.

Regan, C.↗
NASA NTRS1984

Peripheral vision displays: The future

Several areas of research relating to peripheral vision displays used by aircraft pilots are outlined: fiber optics, display color, and holography. Various capacities and specifications of gas and solid state lasers are enumerated. These lasers are potential sources of green light for the peripheral vision displays. The relative radiance required for rod and cone vision at different wavelengths is presented graphically. Calculated and measured retinal sensitivities (foveal and peripheral) are given for wavelength produced by various lasers.

Assenhein, H. M.↗
NASA NTRS1985

Reconstruction of a 3-dimensional transonic rotor flow field from holographic interferogram data

Holographic interferometry and computer-assisted tomography (CAT) are used to determine the transonic velocity field of a model rotor blade in hover. A pulsed ruby laser recorded 40 interferograms with a 2-ft-diam view field near the model rotor-blade tip operating at a tip Mach number of 0.90. After digitizing the interferograms and extracting fringe-order functions, the data are transferred to a CAT code. The CAT code then calculates the perturbation velocity in seeral planes above the blade surface. The values from the holography-CAT method compare favorably with previously obtained numerical computations in most locations near the blade tip. The results demonstrate the technique's potential for three-dimensional transonic rotor flow studies.

Yu, Y. H.↗
NASA NTRS1984

Comparative measurements using different particle size instruments

This paper discusses the measurement and comparison of particle size and velocity measurements in sprays. The general nature of sprays and the development of standard, consistent research sprays are described. The instruments considered in this paper are: pulsed laser photography, holography, television, and cinematography; laser anemometry and interferometry using visibility, peak amplitude, and intensity ratioing; and laser diffraction. Calibration is by graticule, reticle, powders with known size distributions in liquid cells, monosize sprays, and, eventually, standard sprays. Statistical analyses including spatial and temporal long-time averaging as well as high-frequency response time histories with conditional sampling are examined. Previous attempts at comparing instruments, the making of simultaneous or consecutive measurements with similar types and different types of imaging, interferometric, and diffraction instruments are reviewed. A program of calibration and experiments for comparing and assessing different instruments is presented.

Chigier, N.↗
NASA NTRS1986

Recording Interferograms Holographically

Images of experiments stored for later analysis Classical interferometer modified for holography by removing entrance semireflecting mirror and inserting holographic recording in one of legs. Collimated laser beam projected through hologram and directed to remaining semitransparent mirror. Combines with reference beam from same laser to form virtual image of original experiment. Developed for experiments on crystal growth during space flights. Images recorded rapidly under constraints of experiments and later examined on ground.

Comeens, E. R.↗