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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Assessing the Reliability of NDE

Versatile FORTRAN computer algorithm developed for calculating and plotting reliability of nondestructive evaluation (NDE) technique for inspection of flaws. Developed specifically to determine reliability of radiographic and ultrasonic methods for detection of critical flaws in structural ceramic materials. Reliability displayed in form of plot of probability of detection versus flaw size. NDE methods used in such applications as diagnostic medicine, quality control in industrial production, and prediction of failure in structural components.

Roth, Don J.↗
NASA NTRS1986

Microgravity Science and Applications

The report presents fifteen papers from a workshop on microgravity science and applications held at the Jet Propulsion Laboratory in Pasadena, California, on December 3 to 4, 1984. The workshop and panel were formed by the Solid State Sciences Committee of the Board on Physics and Astronomy of the National Research Council in response to a request from the Office of Science and Technology Policy. The goal was to review the microgravity science and applications (MSA) program of NASA and to evaluate the quality of the program. The topics for the papers are metals and alloys, electronic materials, ceramics and glasses, biotechnology, combustion science, and fluid dynamics.

Source record↗
NASA NTRS1987

Fracture mechanics concepts in reliability analysis of monolithic ceramics

Basic design concepts for high-performance, monolithic ceramic structural components are addressed. The design of brittle ceramics differs from that of ductile metals because of the inability of ceramic materials to redistribute high local stresses caused by inherent flaws. Random flaw size and orientation requires that a probabilistic analysis be performed in order to determine component reliability. The current trend in probabilistic analysis is to combine linear elastic fracture mechanics concepts with the two parameter Weibull distribution function to predict component reliability under multiaxial stress states. Nondestructive evaluation supports this analytical effort by supplying data during verification testing. It can also help to determine statistical parameters which describe the material strength variation, in particular the material threshold strength (the third Weibull parameter), which in the past was often taken as zero for simplicity.

Manderscheid, Jane M.↗
NASA NTRS1987

Advanced Gas Turbine (AGT) Technology Development Project

This report is the eleventh in the series of Technical Summary reports for the Advanced Gas Turbine (AGT) Technology Development Project, authorized under NASA Contract DEN3-167, and sponsored by the Department of Energy (DOE). This report was prepared by Garrett Turbine Engine Company, A Division of the Garrett Corporation, and includes information provided by Ford Motor Company, the Standard Oil Company, and AiResearch Casting Company. This report covers plans and progress for the period July 1, 1985 through June 30, 1986. Technical progress during the reported period was highlighted by the 85-hour endurance run of an all-ceramic engine operating in the 2000 to 2250 F temperature regime. Component development continued in the areas of the combustion/fuel injection system, regenerator and seals system, and ceramic turbine rotor attachment design. Component rig testing saw further refinements. Ceramic materials showed continued improvements in required properties for gas turbine applications; however, continued development is needed before performance and reliability goals can be set.

Source record↗
NASA NTRS1986

Nondestructive Evaluation (NDE) of structural ceramics by photoacoustic microscopy

Photoacoustic microscopy (PAM) was utilized to detect surface and subsurface defects in structural ceramic materials. A computerized PAM data acquisition, color imaging and analysis system was developed and used. Subsurface simulated cylindrical holes can be detected to about 1 mm below the interrograting surface. Simulated tight surface cracks of 96 microns length and 48 microns depth can be detected in these materials under optimum conditions.

Khandelwal, P. K.↗
NASA NTRS1986

Fractographic and microstructural evaluation of 3500-hour durability specimens

Long term durability testing of candidate ceramic materials for advanced gas turbine applications was performed. Specimens of the materials were exposed to combustion atmospheres under temperature cyclic conditions for times up to 3500 hours and at peak temperatures of 1200 and 1370 C. The specimen strengths after exposure were measured at room temperature and at 1200 C. In addition, a number of physical measurements were taken; however, no microstructural examination of the specimens was performed. Materials examined include: sintered alpha silicon carbide, sintered silicon nitride, and reaction bonded silicon nitride. Sample preparation techniques were developed to provide high quality thin-section specimens which can be examined by transmitted light or thinned using an ion mill for subsequent transmission electron microscopic examination. Specimen preparation techniques and the results of optical and electron microscopic examination of the reaction interfaces of the selected specimens are presented.

Miller, A. D.↗
NASA NTRS1989

Grinding Si3N4 Powder In Si3N4 Equipment

Three methods of grinding compared. Report based on study of grinding silicon nitride powder in preparation for sintering into solid ceramic material. Attrition, vibratory, and ball mills lined with reaction-bonded silicon nitride tested. Rates of reduction of particle sizes and changes in chemical compositions of powders measured so grinding efficiences and increases in impurity contents from wear of mills and media evaluated for each technique.

Herbell, Thomas P.↗
NASA NTRS1988

Sensors for ceramic components in advanced propulsion systems: Summary of literature survey and concept analysis, task 3 report

The results of a literature survey and concept analysis related to sensing techniques for measuring of surface temperature, strain, and heat flux for (non-specific) ceramic materials exposed to elevated temperatures (to 2200 K) are summarized. Concepts capable of functioning in a gas turbine hot section environment are favored but others are reviewed also. Recommendation are made for sensor development in each of the three areas.

Bennethum, W. H.↗
NASA NTRS1989

Rapid fabrication of lightweight ceramic mirrors via chemical vapor deposition

Lightweight Si/SiC mirrors of nominal diameter 7.5 cm have been fabricated via a scalable and rapid CVD process to demonstrate the CVD mirror fabrication technology. These mirrors consist of a faceplate of either Si or Si-coated SiC and a lightweight backstructure made of either Si or SiC. The mirrors were polished to a figure better than 1/5th of a wave at 0.6328 A and a finish of better than 10 A rms. A procedure for fabricating these mirrors is described. The CVD fabrication process is fast and has the potential to yield several mirrors in a few weeks time from a single reactor. The CVD mirror fabrication technology is quite general and can be extended to include mirrors of other ceramic materials such as TiB2 and B4C.

Goela, Jitendra S.↗
NASA NTRS1990

Friction And Wear Of Silicon Ceramics

Report presents results of experimental study of friction and wear in unlubricated sliding of silicon-based ceramics on Inconel(R) 718 nickel-based alloy. Both monolithic and fiber-reinforced ceramics tested at temperatures from 25 to 800 degrees C. Evaluates ceramic materials for potential use as cylinder liners, piston caps, and other engine parts subjected to sliding or rubbing.

Deadmore, Daniel L.↗
NASA NTRS1990

Temperature Rises In Pumps For Superfluid Helium

Report discusses increases in temperature of superfluid helium in centrifugal and fountain-effect pumps. Intended for use in transfers of superfluid helium in outer space. Increases in temperature significantly affect losses during transfers and are important in selection of temperatures of supply tanks. Purpose of study, increase in temperature in fountain-effect pump calculated on basis of thermodynamic considerations, starting from assumption of ideal pump. Results of recent tests of ceramic material intended for use in such pumps support this assumption. Overall, centrifugal pumps more effective because it produces smaller rise in temperature.

Kittel, Peter↗
NASA NTRS1989

Plasma-deposited amorphous hydrogenated carbon films and their tribological properties

Recent work on the properties of diamondlike carbon films and their dependence on preparation conditions are reviewed. The results of the study indicate that plasma deposition enables one to deposit a variety of amorphous hydrogenated carbon (a-C:H ) films exhibiting more diamondlike behavior to more graphitic behavior. The plasma-deposited a-C:H can be effectively used as hard, wear-resistant, and protective lubricating films on ceramic materials such as Si(sub 3)N(sub 4) under a variety of environmental conditions such as moist air, dry nitrogrn, and vacuum.

Miyoshi, Kazuhisa↗
NASA NTRS1990

Thermal/structural analyses of several hydrogen-cooled leading-edge concepts for hypersonic flight vehicles

The aerodynamic heating at high flight Mach numbers, when shock interference heating is included, can be extremely high and can exceed the capability of most conventional metallic and potential ceramic materials available. Numerical analyses of the heat transfer and thermal stresses are performed on three actively cooled leading-edge geometries (models) made of three different materials to address the issue of survivability in a hostile environment. These analyses show a mixture of results from one configuration to the next. Results for each configuration are presented and discussed. Combinations of enhanced internal film coefficients and high material thermal conductivity of copper and tungsten are predicted to maintain the maximum wall temperature for each concept within acceptable operating limits. The exception is the TD nickel material which is predicted to melt for most cases. The wide range of internal impingement film coefficients (based on correlations) for these conditions can lead to a significant uncertainty in expected leading-edge wall temperatures. The equivalent plastic strain, inherent in each configuration which results from the high thermal gradients, indicates a need for further cyclic analysis to determine component life.

Gladden, Herbert J.↗
NASA NTRS1990

Fracture toughness and crack growth of Zerodur

The fracture toughness and crack growth parameters of Zerodur, a low expansion glass ceramic material, were determined. The fracture toughness was determined using indentation techniques and was found to be 0.9 MPa x m(sup 1/2). The crack growth parameters were determined using indented biaxial specimens subjected to static and dynamic loading in an aqueous environment. The crack growth parameters n and 1n(B) were found to be 30.7 and -6.837, respectively. The crack growth parameters were also determined using indented biaxial specimens subjected to dynamic loading in an ambient 50 percent relative humidity environment. The crack growth parameters n and 1n(B) at 50 percent relative humidity were found to be 59.3 and -17.51, respectively.

Viens, Michael J.↗
NASA NTRS1990

Thermal/structural analyses of several hydrogen-cooled leading-edge concepts for hypersonic flight vehicles

The aerodynamic heating at high flight Mach numbers, when shock interference heating is included, can be extremely high and can exceed the capability of most conventional metallic and potential ceramic materials available. Numerical analyses of the heat transfer and thermal stresses are performed on three actively cooled leading-edge geometries (models) made of three different materials to address the issue of survivability in a hostile environment. These analyses show a mixture of results from one configuration to the next. Results for each configuration are presented and discussed. Combinations of enhanced internal film coefficients and high material thermal conductivity of copper and tungsten are predicted to maintain the maximum wall temperature for each concept within acceptable operating limits. The exception is the TD nickel material which is predicted to melt for most cases. The wide range of internal impingement film coefficients (based on correlations) for these conditions can lead to a significant uncertainty in expected leading-edge wall temperatures. The equivalent plastic strain, inherent in each configuration which results from the high thermal gradients, indicates a need for further cyclic analysis to determine component life.

Gladden, Herbert J.↗
NASA NTRS1989

Plasma-deposited amorphous hydrogenated carbon films and their tribological properties

Recent work on the properties of diamondlike carbon films and their dependence on preparation conditions are reviewed. The results of the study indicate that plasma deposition enables one to deposit a variety of amorphous hydrogenated carbon (a-C:H) films exhibiting more diamondlike behavior to more graphitic behavior. The plasma-deposited a-C:H can be effectively used as hard, wear-resistant, and protective lubricating films on ceramic materials such as Si(sub 3)N(sub 4) under a variety of environmental conditions such as moist air, dry nitrogen, and vacuum.

Miyoshi, K.↗
NASA NTRS1991

Making Three-Layer Solid Electrolyte/Electrode Sandwiches

Tape-casting-and-sintering process joins two ceramic materials having widely different sintering temperatures into integral sandwich structure. Layers retain their identities, without migration of constituents. Used to make three-layer structure composed of outer porous layers of strontium-doped lanthanum manganite and inner dense layer of yttria-stabilized zirconia. Structures used to make electrolytic and fuels cells with solid electrolytes for use at high temperatures. Other potential applications include oxygen pumps and oxygen sensors.

Schroeder, James E.↗
NASA NTRS1991

Survey of results from the Boeing modules on the M0003 experiment on LDEF

The Boeing modules on the M0003 experiment included fiber optics, ceramic materials, a variety of electronic piece parts, composites and thermal control paints, fasteners, thin film lubricants, anodized surfaces, and adhesives. These materials were flown on the leading and trailing edge exteriors, and on the interior portion of LDEF M0003 providing exposure under three distinct environments. The condition of each of these material types is described. Results of optical, surface, and mechanical properties are presented.

Pippin, H. Gary↗