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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Automatic differentiation for design sensitivity analysis of structural systems using multiple processors

An automatic differentiation tool (ADIFOR) is incorporated into a finite element based structural analysis program for shape and non-shape design sensitivity analysis of structural systems. The entire analysis and sensitivity procedures are parallelized and vectorized for high performance computation. Small scale examples to verify the accuracy of the proposed program and a medium scale example to demonstrate the parallel vector performance on multiple CRAY C90 processors are included.

Nguyen, Duc T.↗
DOE OSTI2013

Ionic conduction, bond valence analysis of structure–property relationships of NaHoP{sub 2}O{sub 7}

Single crystals of NaHoP{sub 2}O{sub 7} diphosphate have been prepared by the flux method and its structural and physical properties have been investigated. It crystallizes in the monoclinic system with the space group P2{sub 1}/n and its parameters are: a=8.6796(4) Å, b=5.3677(2) Å, c=13.6904(6) Å, β=106.120° (2), V=612.75 (5) Å{sup 3}, Z=4. The structure of NaHoP{sub 2}O{sub 7} consists of a three-dimensional framework of HoO{sub 6} octahedra, linked by P{sub 2}O{sub 7} diphosphate units, forming tunnels running parallel to [0 1 0], which are occupied by Na atoms. The infrared and Raman vibrational spectra have been investigated. Activation energy was obtained from Arrhenius plots (Ln σT versus 1000/T) and found to be 1.27 eV. The coupling of the structural analysis with the BVS model for NaHoP{sub 2}O{sub 7} has better interpret the measurements of the ionic conductivity and the most probably transport pathway model was determined. - Graphical abstract: Schematic representation of the structural arrangement of NaHoP{sub 2}O{sub 7} shows the sodium conduction pathway along the [0 1 0] direction. Highlights: • Single crystals of NaHoP{sub 2}O{sub 7} were prepared by flux method and characterized by single-crystal X-ray data. • The conductivity and loss spectra were analysed in order explain the mechanism of conduction. • The most probably conduction pathway are determined.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Development of load-dependent Ritz vector method for structural dynamic analysis of large space structures

The development and preliminary assessment of a method for dynamic structural analysis based on load-dependent Ritz vectors are presented. The vector basis is orthogonalized with respect to the mass and structural stiffness in order that the equations of motion can be uncoupled and efficient analysis of large space structure performed. A series of computer programs was developed based on the algorithm for generating the orthogonal load-dependent Ritz vectors. Transient dynamic analysis performed on the Space Station Freedom using the software was found to provide solutions that require a smaller number of vectors than the modal analysis method. Error norm based on the participation of the mass distribution of the structure and spatial distribution of structural loading, respectively, were developed in order to provide an indication of vector truncation. These norms are computed before the transient analysis is performed. An assessment of these norms through a convergence study of the structural response was performed. The results from this assessment indicate that the error norms can provide a means of judging the quality of the vector basis and accuracy of the transient dynamic solution.

Ricles, James M.↗
NASA NTRS1977

The vehicle design evaluation program - A computer-aided design procedure for transport aircraft

The vehicle design evaluation program is described. This program is a computer-aided design procedure that provides a vehicle synthesis capability for vehicle sizing, external load analysis, structural analysis, and cost evaluation. The vehicle sizing subprogram provides geometry, weight, and balance data for aircraft using JP, hydrogen, or methane fuels. The structural synthesis subprogram uses a multistation analysis for aerodynamic surfaces and fuselages to develop theoretical weights and geometric dimensions. The parts definition subprogram uses the geometric data from the structural analysis and develops the predicted fabrication dimensions, parts material raw stock buy requirements, and predicted actual weights. The cost analysis subprogram uses detail part data in conjunction with standard hours, realization factors, labor rates, and material data to develop the manufacturing costs. The program is used to evaluate overall design effects on subsonic commercial type aircraft due to parameter variations.

Oman, B. H.↗
NASA NTRS1976

Titanium and advanced composite structures for a supersonic cruise arrow wing configuration

Structural design studies were made, based on current technology and on an estimate of technology to be available in the mid 1980's, to assess the relative merits of structural concepts and materials for an advanced arrow wing configuration cruising at Mach 2.7. Preliminary studies were made to insure compliance of the configuration with general design criteria, integrate the propulsion system with the airframe, and define an efficient structural arrangement. Material and concept selection, detailed structural analysis, structural design and airplane mass analysis were completed based on current technology. Based on estimated future technology, structural sizing for strength and a preliminary assessment of the flutter of a strength designed composite structure were completed. An advanced computerized structural design system was used, in conjunction with a relatively complex finite element model, for detailed analysis and sizing of structural members.

Turner, M. J.↗