Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “STRENGTH CALCULATIONS”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Infrared Band Strengths for Amorphous and Crystalline Methyl Propionate, a Candidate Interstellar Molecule

Mid-infrared spectra of amorphous and crystalline methyl propionate, CH3CH2COOCH3, are presented for the first time from a single laboratory, along with measurements of the refractive index of each solid form. Density estimates are made and IR band strengths and absorption coefficients are calculated. Vapor pressures of crystalline methyl propionate at 140-150 K are reported along with an enthalpy of sublimation. Spectroscopic results are compared to a recent study of this compound, and the phase of methyl propionate in that work is identified. Several applications are described.

Astrochemistry↗
NASA NTRS1967

Computer program FPIP-REV calculates fission product inventory for U-235 fission

Computer program calculates fission product inventories and source strengths associated with the operation of U-235 fueled nuclear power reactor. It utilizes a fission-product nuclide library of 254 nuclides, and calculates the time dependent behavior of the fission product nuclides formed by fissioning of U-235.

Brown, W. S.↗
NASA NTRS2000

Mechanical Properties of LaRC(tm) SI Polymer for a Range of Molecular Weights

Mechanical testing of an advanced polyimide resin (LaRC(tm)-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. Elastic and inelastic properties were characterized as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. The combined analysis of calculated yield stress and notched tensile strength indicated that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microphotographs of the failure surfaces also supported these findings.

Whitley, Karen S.↗
NASA NTRS1986

Particle dispersion in confined turbulent swirling flows

This paper reports a numerical investigation of confined swirling flows of gas-particle mixtures. A recently developed two-fluid, multiple-scale mixing model is applied to study the influence of particles on the intensity of the reverse flows of the gas phase and the effects of swirl on the particle dispersion in an annular expanding chamber under isothermal condition. The calculations were made for different swirl strength of injection of the annular jet into the mixing chamber. Results agree well qualitatively with experimental information available. It is also found that the calculated flow fields depend heavily on the prescription of the inlet flow conditions.

Chen, C. P.↗
NASA NTRS1995

Tensile Behavior of Al2o3/feal + B and Al2o3/fecraly Composites

The feasibility of Al2O3/FeAl + B and Al2O3/FeCrAlY composites for high-temperature applications was assessed. The major emphasis was on tensile behavior of both the monolithics and composites from 298 to 1100 K. However, the study also included determining the chemical compatibility of the composites, measuring the interfacial shear strengths, and investigating the effect of processing on the strength of the single-crystal Al2O3 fibers. The interfacial shear strengths were low for Al203/FeAl + B and moderate to high for Al203/FeCrAlY. The difference in interfacial bond strengths between the two systems affected the tensile behavior of the composites. The strength of the Al203 fiber was significantly degraded after composite processing for both composite systems and resulted in poor composite tensile properties. The ultimate tensile strength (UTS) values of the composites could generally be predicted with either rule of mixtures (ROM) calculations or existing models when using the strength of the etched-out fiber. The Al2O3/FeAl + B composite system was determined to be unfeasible due to poor interfacial shear strengths and a large mismatch in coefficient of thermal expansion (CTE). Development of the Al2O3/FeCrAlY system would require an effective diffusion barrier to minimize the fiber strength degradation during processing and elevated temperature service.

Draper, S. L.↗
NASA NTRS2014

Ab Initio Modeling of Molecular Radiation

Radiative emission from excited states of atoms and molecules can comprise a significant fraction of the total heat flux experienced by spacecraft during atmospheric entry at hypersonic speeds. For spacecraft with ablating heat shields, some of this radiative flux can be absorbed by molecular constituents in the boundary layer that are formed by the ablation process. Ab initio quantum mechanical calculations are carried out to predict the strengths of these emission and absorption processes. This talk will describe the methods used in these calculations using, as examples, the 4th positive emission bands of CO and the 1g+ 1u+ absorption in C3. The results of these calculations are being used as input to NASA radiation modeling codes like NeqAir, HARA and HyperRad.

spectroscopy↗
NASA NTRS1983

Q branches in the rotational spectrum of HOCl

The far IR rotational spectrum of HOCl from 70-263/cm have been obtained. The most prominent features of the rotational spectrum are the Q branches, for which positions have been measured. Statistical strengths for the Q branches have been calculated and mu sub b, the component of the dipole moment that allows Q branch transitions, has been determined from P and R branch line intensities. It is found that mu sub b = 1.4 + or - 0.2 D. Q branch strengths and shifts at stratospheric temperature are calculated.

Chance, K. V.↗
NASA NTRS1987

Changes in measured vector magnetic fields when transformed into heliographic coordinates

The changes that occur in measured magnetic fields when they are transformed into a heliographic coordinate system are investigated. To carry out this investigation, measurements of the vector magnetic field of an active region that was observed at 1/3 the solar radius from disk center are taken, and the observed field is transformed into heliographic coordinates. Differences in the calculated potential field that occur when the heliographic normal component of the field is used as the boundary condition rather than the observed line-of-sight component are also examined. The results of this analysis show: (1) that the observed fields of sunspots more closely resemble the generally accepted picture of the distribution of umbral fields if they are displayed in heliographic coordinates; (2) that the differences in the potential calculations are less than 200 G in field strength and 20 deg in field azimuth outside sunspots; and (3) that differences in the two potential calculations in the sunspot areas are no more than 400 G in field strength but range from 60 to 80 deg in field azimuth in localized umbral areas.

Hagyard, M. J.↗
NASA NTRS1971

On the He(plus) triplet line intensities

The theoretical calculations of helium triplet line strengths, including collisional enhancement, are compared to astronomical observations. Both are plotted on an I(10830)/I(5876) vs I(5876)/I(4471) plane. It appears that the theory of helium triplet line strengths agrees with present observations, and that the question of an additional depopulation mechanism for the 2 3S population is probably predicted correctly within 30%.

Daltabuit, E.↗
NASA NTRS1972

Model potential calculations of lithium transitions.

Semi-empirical potentials are constructed that have eigenvalues close in magnitude to the binding energies of the valence electron in lithium. The potentials include the long range polarization force between the electron and the core. The corresponding eigenfunctions are used to calculate dynamic polarizabilities, discrete oscillator strengths, photoionization cross sections and radiative recombination coefficients. A consistent application of the theory imposes a modification on the transition operator, but its effects are small for lithium. The method presented can be regarded as a numerical generalization of the widely used Coulomb approximation.

Caves, T. C.↗
NASA NTRS1980

The implications of hydrogen emission line ratios in quasi-stellar objects

The results of multilevel, depth-dependent, fully interlocked radiative transfer calculations for hydrogen emission line strengths in a single QSO emission line cloud (ELC) are summarized. The hydrogen-line forming region of the ELC is found to be quite thick (tau sub el between 1,000 and 100,000), which is consistent with heating of a pure hydrogen cloud by photoionization. Results indicate that the volume-averaged escape probability approach introduces large errors by assuming, in effect, that a single point in the ELC is representative of the emergent radiation; that the influence of frequency redistribution on the photon escape probability in resonance and subordinate lines must be explicitly recognized, and that full consistency between excitation and ionization processes must be maintained.

Canfield, R. C.↗
NASA NTRS1985

Confined turbulent swirling recirculating flow predictions

The capability and the accuracy of the STARPIC computer code in predicting confined turbulent swirling recirculating flows is presented. Inlet flow boundary conditions were demonstrated to be extremely important in simulating a flowfield via numerical calculations. The degree of swirl strength and expansion ratio have strong effects on the characteristics of swirling flow. In a nonswirling flow, a large corner recirculation zone exists in the flowfield with an expansion ratio greater than one. However, as the degree of inlet swirl increases, the size of this zone decreases and a central recirculation zone appears near the inlet. Generally, the size of the central zone increased with swirl strength and expansion ratio. Neither the standard k-epsilon turbulence mode nor its previous extensions show effective capability for predicting confined turbulent swirling recirculating flows. However, either reduced optimum values of three parameters in the mode or the empirical C sub mu formulation obtained via careful analysis of available turbulence measurements, can provide more acceptable accuracy in the prediction of these swirling flows.

Abujelala, M. T.↗
NASA NTRS1987

Magnetic field and current structures in the magnetosphere of Uranus

Voyager 2 magnetic field and plasma data are compared with theoretical model calculations for the magnetosphere of Uranus to derive a global picture from the limited set of measurements. The results suggest that Voyager 2 entered the Uranian magnetosphere during a relaxation phase which followed a compression of the entire magnetosphere. The plasma beta values in the Uranian neutral sheet were found to be smallar by a factor of 3-8 compared to corresponding beta values in the average terrestrial neutral sheet. The excellent agreement found between observed and calculated magnetic tail lobe field strengths indicates that the Uranian magnetosphere reaches the state of quasi-static (i.e., slowly time-dependent MHD equilibrium).

Voigt, G.-H.↗
NASA NTRS1989

Infrared spectroscopy of astrophysical ices - New insights in the photochemistry

The photochemical effects of the interstellar radiation field on the ice mantles of molecular-cloud dust grains are investigated by means of laboratory simulations. The apparatus and analytical methods described by Hagen et al. (1979) and Hagen (1982) are employed, and the results are presented as spectra and discussed in detail. Consideration is given to the strong IR absorption bands of OCN(-) and NH4(+) which appear after photolysis and heating of H2O/NH3/CO/O2 ices, the detection of similar bands toward W33A, the critical role of NH3 in the photochemical production of ions, and the use of calculated integrated absorption-band strengths to estimate astrophysical column densities.

Grim, R. J. A.↗
NASA NTRS1991

Mechanical behavior of fiber reinforced SiC/RBSN ceramic matrix composites: Theory and experiment

The mechanical behavior of continuous fiber reinforced SiC/RBSN (Reaction Bonded Silicon Nitride) composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE (nondestructive evaluation) techniques through the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength, and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.

Chulya, Abhisak↗
NASA NTRS1991

Mechanical behavior of fiber reinforced SiC/RBSN ceramic matrix composites - Theory and experiment

The mechanical behavior of continuous fiber reinforced SiC/RBSN (Reaction Bonded Silicon Nitride) composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE (nondestructive evaluation) techniques throughout the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorproating residual stresses to calculate the critical matrix cracking strength, ultimate strength, and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.

Chulya, Abhisak↗
NASA NTRS1992

Post impact compressive behavior of composites

In this paper, the post impact compressive behavior of polymeric composites is studied both analytically and experimentally. In the analytical study, a closed-form solution is obtained for postbuckling of composites with a circular delamination. Using this solution, the reduced stiffness of the impact damaged region is calculated and the residual compressive strengths of quasi-isotropic laminates are predicted as a function of damage size. In the experimental study, in-plane displacements near the damaged region are determined by employing a micro moire interferometry technique. The strain concentrations as well as the compression-after-impact strength have been measured and compared with analytical predictions. Good agreement between the predicted results and experimental data was observed.

Lin, Kuen Y.↗