Search NASA⌕ Search

SEARCH · Search NASA

Results for “COMPOSITE MODELS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Geophysical constraints on lunar bulk composition and structure - A reassessment

Theoretical lunar mantle seismic velocity and density profiles were calculated for a series of specific bulk composition models, thermal models, and evolutionary models. It was found that most of the calculated seismic profiles are in qualitative agreement with the Nakamura (1983) observational mantle seismic velocity model. With respect to the density modeling results, the most interesting finding is that none of the considered models yield mantle density increases that are sufficient to match the adapted upper bound on the lunar moment-of-inertia factor (0.3928). The results suggest that the moon possesses a dense metallic core with a mass in the range of 1 to 4 percent of the lunar mass and that the alumina-rich models of Morgan et al. (1978) and Taylor (1982) are best able to match the middle mantle velocity increase that characterizes the Nakamura model.

Hood, L. L.↗
NASA NTRS1989

Airborne infrared spectroscopy of Comet Wilson (1986l) and comparisons with Comet Halley

H2O and possibly CH4 have been detected in near-infrared spectra of Comet Wilson (1986l). The observed number and relative intensities of cometary H2O lines in the nu3 band at 2.65 microns were consistent with fluorescent excitation pumped by solar infrared photons. The H2O production rate in Comet Wilson was approximately 3 x 10 to the 29th/s at R = 1.2 AU; no pronounced temporal variability was observed. Lines in the nu3 band of CH4 at 3.3 microns were possibly detected at the 3 sigma confidence level. The CH4 abundance is in the range CH4/H2O = 0.014-0.045; the uncertainty is due primarily to the assumed effective excitation temperature of CH4. The CH4 abundance in this dynamically 'new' comet is similar to that observed in P/Halley. These values are low for equilibrium compositional models and very high for disequilibrium condensation in the solar nebula.

Larson, Harold P.↗
NASA NTRS1991

The use of transition heights for the representation of ion composition

Several characteristic transition heights can be found in ionospheric ion-composition profiles. These are the boundaries between the regions dominated by light ions, atomic oxygen ions, molecular ions, and cluster ions, respectively. Ion-composition modeling can benefit from the use of these transition heights. Special emphasis is given to the 'upper' transition height H sub T (light ions to atomic oxygen) and to the 'lower' transition height h sub t (atomic oxygen to molecular ions). Transition-height models deduced from rocket and satellite measurements are compared with the heights predicted by the International Reference Ionosphere. Considerable discrepancies are found between the different models as well as between the models and independent measurements.

Bilitza, Dieter↗
NASA NTRS1991

Variational mechanics analysis of the stresses in microdrop debond specimens

A recently derived variational mechanics analysis of stresses in single-fiber model composites has been applied to the analysis of the stresses in the microdrop debond specimen. The new analysis is more accurate than the commonly applied shear-lag or elastic-plastic analyses. The results from a sample stress state calculation suggest that interfacial failure between the fiber and the microdrop is by mode I or opening mode failure at the beginning of the microdrop. The opening mode failure is caused by a large tensile radial stress at the fiber/matrix interface. Previous analyses of microdrop debond data have been in terms of a shear strength. It is suggested that these analyses misrepresent microdrop debond results and recommend instead a failure analysis based on energy release rate and interfacial fracture toughness. A procedure for calculating the energy release rate for the growth of an interfacial crack is described.

Scheer, Robert J.↗
NASA NTRS1992

Surface chemistry and mineralogy

The accumulated knowledge on the chemistry and mineralogy of Martian surface materials is reviewed. Pertinent information obtained by direct analyses of the soil on Mars by the Viking Landers, by remote sensing of Mars from flyby and orbiting spacecraft, by telescopic observations from earth, and through detailed analyses of the SNC meteorites presumed to be Martian rocks are summarized and analyzed. A compositional model for Mars soil, giving selected average elemental concentrations of major and trace elements, is suggested. It is proposed that the fine surface materials on Mars are a multicomponent mixture of weathered and nonweathered minerals. Smectite clays, silicate mineraloids similar to palagonite, and scapolite are suggested as possible major candidate components among the weathered minerals.

Banin, A.↗
NASA NTRS1994

Predicting Flow-Induced Vibrations In A Convoluted Hose

Composite model constructed from two less accurate models. Predicts approximately frequencies and modes of vibrations induced by flows of various fluids in convoluted hose. Based partly on spring-and-lumped-mass representation of dynamics involving springiness and mass of convolution of hose and density of fluid in hose.

Harvey, Stuart A.↗
NASA NTRS1994

Theoretical investigation of variable periodicity (graded) multilayers for hard x ray applications

The objective of this research was to investigate the possibility of increasing the useful bandwidth of multilayer mirrors. Mirrors 'constructed' with non-periodically spaced reflecting surfaces were considered. These structures included depth-graded and laterally-graded mirrors as well as those with reflectors located via a log-periodic spacing rule. No enhancement of bandwidth resulted from simulations of simple versions of any of the three non-periodic mirrors. However, certain depth-graded structures did exhibit reflectances essentially the same as from uniform mirrors. Moreover, it was found that some control was possible regarding the location (with respect to energy) of the maximum reflectance peak. Effective bandwidth was increased when composite models were simulated. In two of the cases studied, bandwidth was enhanced by a factor of approximately 3. One model consisted of a depth-graded mirror constructed with three separately defined structures, or blocks. Each block consisted of two layer-pairs repeated three times. Then, the entire 18 layer-pair group was repeated several times. Simulation of this 3 block depth-graded configuration yielded three reflectance peaks, one representative of each depth-graded block. The other configurations resulting in enhanced bandwidth assumed independently constructed mirrors immediately adjacent to each other and sharing the same substrate. Reflectance peaks from each mirror appeared in the response. Both basic models show greatly enhanced effective bandwidths even though the reflectance curves appear as non-overlapping for these specific models. Additionally, these configurations are realizable. Details are contained in the section, DESIGN SIMULATIONS.

Kinney, Ralph A.↗
NASA NTRS1994

Analysis of random structure-acoustic interaction problems using coupled boundary element and finite element methods

A coupled boundary element (BEM)-finite element (FEM) approach is presented to accurately model structure-acoustic interaction systems. The boundary element method is first applied to interior, two and three-dimensional acoustic domains with complex geometry configurations. Boundary element results are very accurate when compared with limited exact solutions. Structure-interaction problems are then analyzed with the coupled FEM-BEM method, where the finite element method models the structure and the boundary element method models the interior acoustic domain. The coupled analysis is compared with exact and experimental results for a simplistic model. Composite panels are analyzed and compared with isotropic results. The coupled method is then extended for random excitation. Random excitation results are compared with uncoupled results for isotropic and composite panels.

Mei, Chuh↗
NASA NTRS1994

COSMIC monthly progress report

Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of May 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are summarized. Nine articles were prepared for publication in the NASA Tech Brief Journal. These articles (included in this report) describe the following software items: (1) WFI - Windowing System for Test and Simulation; (2) HZETRN - A Free Space Radiation Transport and Shielding Program; (3) COMGEN-BEM - Composite Model Generation-Boundary Element Method; (4) IDDS - Interactive Data Display System; (5) CET93/PC - Chemical Equilibrium with Transport Properties, 1993; (6) SDVIC - Sub-pixel Digital Video Image Correlation; (7) TRASYS - Thermal Radiation Analyzer System (HP9000 Series 700/800 Version without NASADIG); (8) NASADIG - NASA Device Independent Graphics Library, Version 6.0 (VAX VMS Version); and (9) NASADIG - NASA Device Independent Graphics Library, Version 6.0 (UNIX Version). Activities in the areas of marketing, customer service, benefits identification, maintenance and support, and dissemination are also described along with a budget summary.

Source record↗
NASA NTRS1995

Concurrent engineering research center

The projects undertaken by The Concurrent Engineering Research Center (CERC) at West Virginia University are reported and summarized. CERC's participation in the Department of Defense's Defense Advanced Research Project relating to technology needed to improve the product development process is described, particularly in the area of advanced weapon systems. The efforts committed to improving collaboration among the diverse and distributed health care providers are reported, along with the research activities for NASA in Independent Software Verification and Validation. CERC also takes part in the electronic respirator certification initiated by The National Institute for Occupational Safety and Health, as well as in the efforts to find a solution to the problem of producing environment-friendly end-products for product developers worldwide. The 3M Fiber Metal Matrix Composite Model Factory Program is discussed. CERC technologies, facilities,and personnel-related issues are described, along with its library and technical services and recent publications.

Callahan, John R.↗
NASA NTRS1994

Demonstration of an elastically coupled twist control concept for tilt rotor blade application

The purpose of this Note is to present results from an analytic/experimental study that investigated the potential for passively changing blade twist through the use of extension-twist coupling. A set of composite model rotor blades was manufactured from existing blade molds for a low-twist metal helicopter rotor blade, with a view toward establishing a preliminary proof concept for extension-twist-coupled rotor blades. Data were obtained in hover for both a ballasted and unballasted blade configuration in sea-level atmospheric conditions. Test data were compared with results obtained from a geometrically nonlinear analysis of a detailed finite element model of the rotor blade developed in MSC/NASTRAN.

Lake, R. C.↗
NASA NTRS1995

Polarimetric signatures of sea ice. 2: Experimental observations

Experimental observations of polarimetric signatures are presented for sea ice in the Beaufort Sea under cold winter conditions and interpreted with the composite model developed in Part 1. Polarimetric data were acquired in March 1988 with the Jet Propulsion Laboratory multifrequency airborne synthetic aperture radar (SAR) during the Beaufort Sea Flight Campaign. The experimental area was located near 75 N latitude and spanned 140 deg-145 deg W longitude. Selected sea ice scenes contain various ice types, including multiyear, thick first-year, and thin lead ice. Additionally, the C band SAR on the first European Remote Sensing Satellite provides supplementary backscattering data of winter Beaufort Sea ice for small incident angles (20 deg-26 deg) at vertical polarization. Sea ice characterization and environment data used in the model were collected at the Applied Physics Laboratory drifting ice station to the northeast of Prudhoe Bay; additional data from field and laboratory experiments are also utilized in this analysis. The model related sea ice polarimetric backscattering signatures to physical, structural, and electromagnetic properties of sea ice. Scattering mechanisms contributing to sea ice signatures are explained, and sensitivies of polarimetric signatures to sea ice characterization parameters are studied.

Nghiem, S. V.↗
NASA NTRS1996

Computing Fiber/Matrix Interfacial Effects In SiC/RBSN

Computational study conducted to demonstrate use of boundary-element method in analyzing effects of fiber/matrix interface on elastic and thermal behaviors of representative laminated composite materials. In study, boundary-element method implemented by Boundary Element Solution Technology - Composite Modeling System (BEST-CMS) computer program.

Goldberg, Robert K.↗
NASA NTRS1998

Studies of Protein Solution Properties Using Osmotic Pressure Measurements

Examination of the protein crystallization process involves investigation of the liquid and solid state and a protein's properties in these states. Liquid state studies such as protein self association in solution by light scattering methods or other methods have been used to examine a protein Is properties and therefore its crystallization process and conditions. Likewise can osmotic pressure data be used to examine protein properties and various published osmotic pressure studies were examined by us to correlate osmotic pressure to protein solution properties. The solution behavior of serum albumin, alpha - chymotrypsin, beta - lactoglobulin and ovalbumin was examined over a range of temperatures, pH values and different salt types and concentrations. Using virial expansion and a local composition model the non ideal solution behavior in form of the activity coefficients (thermodynamic) was described for the systems. This protein activity coefficient data was related to a protein's solubility behavior and this process and the results will be presented.

Agena, S.↗
NASA NTRS2001

Physical Properties of Centaur Objects

Centaurs are objects in unstable orbits that cross the orbits of the giant planets. They are presumed to be recent additions to the planetary zone of the Solar System, having been dynamically perturbed from the Kulper Disk by the gravitational action of Neptune. Telescopic observations of Centaurs are important because they give us a view of the composition (and in some cases cometary activity) of large bodies that are normally to far from the Sun to be studied in detail. This paper reports on physical observations, primarily through spectroscopy, of the compositions of a small number of Centaurs that have been studied to date. In particular, the composition of 5145 Pholus is reviewed, following the published work of Crulkshank et al., in which compositional models that fit the spectrum well included H2O ice, the organic solid Titan tholin, a light hydrocarbon ice (e.g., CH3OH), the silicate mineral olivine, and amorphous carbon. The Centaur 1997 CU(26) shows evidence for H2O ice, but nothing else is yet identified.

Cruikshank, Dale P.↗
NASA NTRS2002

Ground and Flight Test Structural Excitation Using Piezoelectric Actuators

A flight flutter experiment at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center, Edwards, California, used an 18-inch half-span composite model called the Aerostructures Test Wing (ATW). The ATW was mounted on a centerline flight test fixture on the NASA F-15B and used distributed piezoelectric strain actuators for in-flight structural excitation. The main focus of this paper is to investigate the performance of the piezoelectric actuators and test their ability to excite the first-bending and first-torsion modes of the ATW on the ground and in-flight. On the ground, wing response resulting from piezoelectric and impact excitation was recorded and compared. The comparison shows less than a 1-percent difference in modal frequency and a 3-percent increase in damping. A comparison of in-flight response resulting from piezoelectric excitation and atmospheric turbulence shows that the piezoelectric excitation consistently created an increased response in the wing throughout the flight envelope tested. The data also showed that to obtain a good correlation between the piezoelectric input and the wing accelerometer response, the input had to be nearly 3.5 times greater than the turbulence excitation on the wing.

Voracek, David F.↗
NASA NTRS2002

The Seyfert-Starburst Connection in X-rays: The Data - 1

We analyze X-ray spectra and images of a sample of Seyfert 2 galaxies that unambiguously contain starbursts, based on their optical and UV characteristics. Although all sample members contain active galactic nuclei (AGNs), supermassive black holes or other related processes at the galactic centers alone cannot account for the total X-ray emission in all instances. Eleven of the 12 observed galaxies are significantly resolved with the ROSAT High Resolution Imager, while six of the eight sources observed with the lower resolution Position Sensitive Proportional Counter also appear extended on larger scales. The X-ray emission is extended on physical scales of 10 kpc and greater, which we attribute to starburst-driven outflows and supernova heating of the interstellar medium. Spectrally, a physically motivated composite model of the X-ray emission that includes a heavily absorbed (N(sub H) greater than 10(exp 23)/sq cm) nuclear component (the AGN), power-law-like scattered AGN flux, and a thermal starburst describes this sample well. Half the sample exhibit iron K(alpha) lines, which are typical of AGNs.

Levenson, N. A.↗
NASA NTRS2003

Production Rates of Noble Gases in the Near-Surface Layers of Europa by Energetic Charged Particles and the Potential for Determining Exposure Ages

The surface of Europa is expected to be extremely active, undergoing tectonic and/or tidal geological activity and sputtering/ deposition, as well as impact cratering. Determination of the actual age of the surface at one or more places would greatly simplify trying to sort out what processes are occurring, and at what rate. If there is K present, as the spectral and compositional modeling discussed predict, it should be possible, in principle, to determine K-Ar crystallization ages. Whether or not there is K present, a consideration of the environment suggests we can determine an energetic particle exposure age if we can make in situ measurements of the abundances of major elements and of noble gas isotopes. This requires instrumentation that is within reach of current technology. In this paper, we calculate production rates for noble-gas isotopes in a simplified Europan surface, to quantify the amount of light noble gases produced by exposure to energetic particles.

Swindle, T. D.↗