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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 685 records · Page 38

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NASA NTRS1991

Braze alloy process and strength characterization studies for 18 nickel grade 200 maraging steel with application to wind tunnel models

A comprehensive study of braze alloy selection process and strength characterization with application to wind tunnel models is presented. The applications for this study include the installation of stainless steel pressure tubing in model airfoil sections make of 18 Ni 200 grade maraging steel and the joining of wing structural components by brazing. Acceptable braze alloys for these applications are identified along with process, thermal braze cycle data, and thermal management procedures. Shear specimens are used to evaluate comparative shear strength properties for the various alloys at both room and cryogenic (-300 F) temperatures and include the effects of electroless nickel plating. Nickel plating was found to significantly enhance both the wetability and strength properties for the various braze alloys studied. The data are provided for use in selecting braze alloys for use with 18 Ni grade 200 steel in the design of wind tunnel models to be tested in an ambient or cryogenic environment.

Bradshaw, James F.↗

NASA NTRS1991

Probabilistic lifetime strength of aerospace materials via computational simulation

The results of a second year effort of a research program are presented. The research included development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic phenomenological constitutive relationship, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects of primitive variables. These primitive variables often originate in the environment and may include stress from loading, temperature, chemical, or radiation attack. This multifactor interaction constitutive equation is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the constitutive equation using actual experimental materials data together with the multiple linear regression of that data.

Boyce, Lola↗

NASA NTRS1991

Computational simulation of high temperature metal matrix composite behavior

Computational procedures are described to simulate the thermal and mechanical behavior of high temperature metal matrix composite (HT MMC) in the following four broad areas: (1) behavior of HT MMC from micromechanics to laminate; (2) HT MMC structural response for simple and complex structural components; (3) HT MMC microfracture; and (4) tailoring of HT MMC behavior for optimum specific performance. Representative results from each area are presented to illustrate the effectiveness of the computational simulation procedures. Relevant reports are referenced for extended discussion regarding the specific area.

Murthy, Pappu L. N.↗

NASA NTRS1990

Structural monitoring of filamentary composites using embedded fiber optics

The feasibility of monitoring overall integrity of structural components made of filamentary composites, by embedding optical fibers between lamina of a composite beam, is investigated using a beam constructed of Kevlar/epoxy cloth with embedded optical fibers aligned with the longitudinal axis of the beam. Phase changes were monitored in three different optical fibers as the composite beam was subjected to pure bending, and the strain response of the fibers was compared to the strain gage readings taken at the surface, showing a strong correlation between the phase change and the applied deformation.

Cashon, John L.↗

NASA NTRS1991

The interstellar D1 line at high resolution

Observations at a resolving power or a velocity resolution are reported of the interstellar D(sub 1) line of Na I in the spectra of Gamma Cas, Delta Ori, Epsilon Ori, Pi Sco, Delta Cyg, and Alpha Cyg. An echelle grating was used in a double-pass configuration with a CCD detector in the coude spectrograph of the 2.7 m reflector at McDonald Observatory. At least 42 kinematically distinct clouds are detected along the light paths to the five more distant stars, in addition to a single cloud seen toward Delta Cyg. The absorption lines arising in 13 of the clouds are sufficiently narrow and unblended to reveal clearly resolved hyperfine structure components split by 1.05 km/s. An additional 13 clouds apparently show comparably narrow, but more strongly blended, lines. For each individual cloud, upper limits T(sub max) and (v sub t) (sub max) on the temperature and the turbulent velocity, respectively, are derived by fitting the observing lines with theoretical absorption profiles.

Hobbs, L. M.↗

NASA NTRS1991

Quantification of uncertainties in coupled material degradation processes - High temperature, fatigue and creep

This paper describes the development of methodology that provides for quantification of uncertainties in lifetime strength of aerospace materials subjected to a number of diverse effects. A probabilistic material degradation model, in the form of a randomized multifactor interaction equation, has been postulated for lifetime strength degradation of structural components of aerospace propulsion systems. The model includes effects that typically reduce lifetime strength and may include temperature, mechanical fatigue, creep and others. The paper also includes the analysis of experimental data from the open literature for Inconel 718. These data are used to provide an initial check for model validity, as well as for calibration of the model's empirical material constants. The model validity check and calibration is carried out for three effects, namely, high temperature, mechanical fatigue and creep.

Boyce, L.↗

NASA NTRS1989

Crashworthy design of helicopter composite airframe structures

The crashworthy behavior of composite materials and generic structural elements is investigated. Cruciform structural elements are crushed in order to determine their energy absorption capability to rotorcraft crash-type loads, and quasi-static compression tests are conducted on a series of aluminum and composite cruciform elements. These elements are representative of keel beam and bulkhead intersections in the subfloor of rotorcraft. Various designs of 'trigger mechanisms' reducing initial peak failure loads and initiating stable crushing failure modes are considered. It is shown that a carbon-fiber-composite/aramid-fiber-composite hybrid element with a columnlike midsection behaves more like a well-designed tubular composite element. Specimens which fail primarily in bending are typical of structural components used in the upper and lower portions of rotorcraft airframes.

Boitnott, Richard L.↗

NASA NTRS1991

Materials and light thermal structures research for advanced space exploration

The Light Thermal Structures Center at the University of Virginia sponsors educational and research programs focused on the development of reliable, lightweight structures to function in hostile thermal environments. Technology advances in materials and design methodology for light thermal structures will contribute to improved space vehicle design concepts with attendant weight savings. This paper highlights current research activities in three areas relevant to space exploration: low density, high temperature aluminum alloys, composite materials, and structures with thermal gradients. Advances in the development of new aluminum-lithium alloys and mechanically alloyed aluminum alloys are described. Material properties and design features of advanced composites are highlighted. Research studies in thermal structures with temperature gradients include inelastic panel buckling and thermally induced unstable oscillations. Current and future research is focused on the integration of new materials with applications to structural components with thermal gradients.

Thornton, Earl A.↗

NASA NTRS1991

Application of finite-element-based solution technologies for viscoplastic structural analyses

Finite-element solution technology developed for use in conjunction with advanced viscoplastic models is described. The development of such solution technology is necessary for performing stress/life analyses of engineering structural problems where the complex geometries and loadings make the conventional analytical solutions difficult. The versatility of the solution technology is demonstrated by applying it to viscoplastic models possessing different mathematical structures and encompassing isotropic and anisotropic materials. The computational results qualitatively replicate deformation behavior observed in experiments on prototypical structural components.

Arya, Vinod K.↗

NASA NTRS1992

Composite-Blade Structural Analyzer

COBSTRAN (COmposite Blade STRuctural ANalyzer) computer program is preprocessor and postprocessor facilitating design and analysis of composite turbofan and turboprop blades, and of composite wind-turbine blades. Combines theories of mechanics of composites and of laminates with data base of fiber and matrix properties. Designed to carry out linear analyses required for efficient mathematical modeling and analysis of bladelike structural components made of multilayered angle-plied fiber composites. Components made from isotropic or anisotropic homogeneous materials also modeled. Written in FORTRAN 77.

Aiello, R. A.↗

NASA NTRS1992

Characteristics Of Superplastically Formed Ti-6242 Sheet

Near-alpha titanium alloy candidate for high-temperature structural airframe applications. Research characterizes selected mechanical properties of Ti-6242 sheets in superplastic forming (SPF) condition, both with and without heat treatment, and compares results with those obtained on as-received material. Information derived from research proves useful to aerospace community for designing and manufacturing Ti-6242 structures and structural components.

Royster, Dick M.↗

NASA NTRS1992

Computational simulation of coupled material degradation processes for probabilistic lifetime strength of aerospace materials

The research included ongoing development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primative variables. These primative variable may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above described constitutive equation using actual experimental materials data together with linear regression of that data, thereby predicting values for the empirical material constraints for each effect or primative variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from the open literature for materials typically of interest to those studying aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Boyce, Lola↗

NASA NTRS1992

Embryogenesis and organogenesis of Carausius morosus under space flight conditions (7-IML-1)

The experiment is part of a radiobiological space research program to obtain experimental data on the biological effectiveness of the structured component of cosmic radiation during spaceflight. In this proposed experiment, Carausius morosus embryos of different ages will develop under spaceflight conditions. The experiment is designed to determine the influence of galactic heavy ions of very high energy deposition in microgravity on developmental processes of different radiation sensitivity and regenerative capacity. Layers of Carausius morosus eggs are sandwiched between different track detectors (cellulose nitrate, CR39). This method allows the localization of the trajectory of each heavy ion in the biological layer and the identification of the site of the penetration inside the egg.

Buecker, D. H.↗

NASA NTRS1992

Unusual materials effects observed on the thermal control surfaces experiment (S0069)

A number of unusual effects were observed on the Thermal Control Surfaces Experiment (TCSE) test samples, front cover, and structural components. These effects include atomic oxygen (AO) texturing of the exposed surface of the silver Teflon (Ag/FEP) thermal control material, 'brownish' discoloration of the Ag/FEP material, changes in fluorescence of thermal control paint samples, and meteoroid/debris impact effects on silver Teflon.

Zwiener, James M.↗

NASA NTRS1990

Radar multipath study for rain-on-radome experiments at the Aircraft Landing Dynamics Facility

An analytical study to determine the feasibility of a rain-on-radome experiment at the Aircraft Landing Dynamics Facility (ALDF) at the Langley Research Center is described. The experiment would measure the effects of heavy rain on the transmission of X-band weather radar signals, looking in particular for sources of anomalous attenuation. Feasibility is determined with regard to multipath signals arising from the major structural components of the ALDF. A computer program simulates the transmit and receive antennas, direct-path and multipath signals, and expected attenuation by rain. In the simulation, antenna height, signal polarization, and rainfall rate are variable parameters. The study shows that the rain-on-radome experiment is feasible with regard to multipath signals. The total received signal, taking into account multipath effects, could be measured by commercially available equipment. The study also shows that horizontally polarized signals would produce better experimental results than vertically polarized signals.

Mackenzie, Anne I.↗

NASA NTRS1991

Laboratory studies in ultraviolet solar physics

The research activity comprised the measurement of basic atomic processes and parameters which relate directly to the interpretation of solar ultraviolet observations and to the development of comprehensive models of the component structures of the solar atmosphere. The research was specifically directed towards providing the relevant atomic data needed to perform and to improve solar diagnostic techniques which probe active and quiet portions of the solar chromosphere, the transition zone, the inner corona, and the solar wind acceleration regions of the extended corona. The accuracy with which the physical conditions in these structures can be determined depends directly on the accuracy and completeness of the atomic and molecular data. These laboratory data are used to support the analysis programs of past and current solar observations (e.g., the Orbiting solar Observatories, the Solar Maximum Mission, the Skylab Apollo Telescope Mount, and the Naval Research Laboratory's rocket-borne High Resolution Telescope and Spectrograph). In addition, we attempted to anticipate the needs of future space-borne solar studies such as from the joint ESA/NASA Solar and Heliospheric Observatory (SOHO) spacecraft. Our laboratory activities stressed two categories of study: (1) the measurement of absolute rate coefficients for dielectronic recombination and electron impact excitation; and (2) the measurement of atomic transition probabilities for solar density diagnostics. A brief summary of the research activity is provided.

Parkinson, W. H.↗

NASA NTRS1990

Applications of composites to armaments

The U.S. Army Materials Technology Laboratory (MTL) has been engaged in investigating the feasibility of applying composite materials to the lightening of artillery structural components since about 1982. In this period a number of efforts were carried out either in-house at MTL or by supporting organizations, including Benet Laboratory and the Oak Ridge National Laboratory, aimed at investigating applications to various components of towed artillery. Salient features of these efforts and some important conclusions that have come out of them are described. In addition to organic matrix composites, discontinuously reinforced metal matrix composites appear to have great potential for weight reduction in this type of application.

Oplinger, Don W.↗

NASA NTRS1992

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Boyce, Lola↗