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  • Weitere Quellen  (189)
  • FLUID MECHANICS AND HEAT TRANSFER  (70)
  • STRUCTURAL MECHANICS  (44)
  • ASTRONAUTICS (GENERAL)  (40)
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  • COMMUNICATIONS AND RADAR
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  • 1990-1994  (189)
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  • 1990  (189)
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  • 1990-1994  (189)
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  • 1
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    Structural monitoring of filamentary composites using embedded fiber optics (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA PAPER 90-3548
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 2
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    Behavior of composite/metal aircraft structural elements and components under crash type loads: What are they telling us (1990)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Failure behavior results are presented from crash dynamics research using concepts of aircraft elements and substructure not necessarily designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs which incorporate improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures which include individual fuselage frames, skeleton subfloors with stringers and floor beams but without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static and dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models. It is believed that the similarity in behavior is giving the designer and dynamists much information about what to expect in the crash behavior of these structures and can guide designs for improving the energy absorption and crash behavior of such structures.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TM-102681 , NAS 1.15:102681 , USAAVSCOM-TR-90-B-003 , AD-A225680
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    Conservative buffering of approximate nonlinear constraints (1990)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: In engineering design practice behavior is usually predicted based on some known nominal design. However, when the design is fabricated it will differ from the nominal design because of manufacturing tolerances. In order to generate nominal designs that will still satisfy behavior constraints in the presence of manufacturing tolerances, engineers resort to the use of safety factors, over and above those introduced to account for other uncertainties (e.g., in load conditions, material properties, analysis modeling). The accurate selection of the values of these manufacturing tolerances safety factors is dependent on the capability of the engineer to determine the sensitivity of the critical constraints to changes in the design variables. This process usually leads to overly conservative designs. The task of choosing safety factors is much more difficult in structural synthesis because: (1) it is not known which constraints will be active at the final design, (2) as the design changes during the synthesis process the sensitivities of the constraints with respect to the design variables also change, and (3) the imposition of the safety factors themselves may change the set of critical constraints. These difficulties can be overcome with the approximation concepts approach to structural synthesis by buffering the approximate constraints with quantities that are related to the design variable tolerances and the accurate sensitivities of the constraints with respect to the design variable. Designs generated by this approach tend to be feasible but not overly conservative.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA, Langley Research Center, Research in Structures, Structural Dynamics and Materials, 1990; p 151-158
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    Analysis of the thermal environment and thermal response associated with thermal-acoustic testing (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A method is developed for predicting the radiant heat flux distribution produced by a bank of quartz radiant heaters which accounts for the specular and diffuse effects of a flat reflector or the diffuse effects of individual parabolic reflectors. This analysis is experimentally verified for a single unreflected lamp and a single lamp with a flat reflector. Observations on the further development of this analysis and experimental validation are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA PAPER 90-0975 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 02, 1990 - Apr 04, 1990; Long Beach, CA; United States
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 5
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    Design and fabrication of an erectable truss for precision segmented reflector application (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The design of a first generation, 4-meter-diameter, doubly-curved, tetrahedral support truss for precision parabolic reflector panels, incorporating joints specifically designed for on-orbit astronaut assembly, is presented. Operational and design features of the erectable joint are detailed. Methods used to achieve very accurate strut lengths are described. Initial static and dynamic truss test results are presented which demonstrate linear structural response and predictability. Truss surface accuracy, determined photogrammetrically, is shown to be within 0.003 inch (RMS) of design.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA PAPER 90-0999 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 02, 1990 - Apr 04, 1990; Long Beach, CA; United States
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 6
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    Spacecraft designs for VSAT networks (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Results are presented from a study to determine the commercial applications of the technology developed for ACTS. Two systems are discussed: point-to-point transmission of T1 (1.544 Mb/s) data channels using Very Small Aperature Terminals, and point-to-point transmission of single channel per carrier data from extremely small ground terminals. Satellite communications systems designed for each of these applications are described.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: AIAA PAPER 90-0895 , AIAA International Communication Satellite Systems Conference and Exhibit; Mar 11, 1990 - Mar 15, 1990; Los Angeles, CA; United States
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 7
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    Mission optimization of the Space Infrared Telescope Facility (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The Space Infrared Telescope Facility (SIRTF) mission based on a cryogenically cooled telescope is described. The SIRTF makes it possible to perform background limited measurements with three focal plane instruments in the wavelength range 2-700 microns over the entire celestial sphere for at least five years. A telescope performance limited by the natural astrophysical background between 2 to 300 microns is achieved by using a superfluid helium cryogenic system for maintaining the forebaffle temperature below 8 K. The attitude control system based on Extreme Ultra-Violet Explorer reaction wheels meets the large and small angle slew requirements and provides 0.15 arc sec pointing stability. The present HEO baseline configuration has a mass of 4370 kg. The future Titan IV/Centaur launch capability to 100,000 km for a SIRTF-sized payload is at least 5770 kg.
    Schlagwort(e): ASTRONAUTICS (GENERAL)
    Materialart: Cryogenic Optical Systems and Instruments IV; Jul 10, 1990 - Jul 12, 1990; San Diego, CA; United States
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 8
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    Convergence of the SMI and the diagonally loaded SMI algorithms with weak interference (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Approximations for the power levels at the output of an adaptive array that uses the diagonally loaded sample-matrix inversion (SMI) algorithm are derived. Diagonal loading is a technique where the diagonal of the covariance matrix is augmented with a positive or negative constant prior to inversion. This paper examines how the signal-to-interference-plus-noise ratio (SINR) and signal-to-interference ratio (SIR) at the array output vary with the number of samples taken when the input signals are CW. It is shown that positive loading produces more rapid convergence with a reduction in output SIR. Negative loading provides an improved SIR level, but positive loading produces more rapid convergence. Negative loading provides an improved SIR level, but the output power levels are erratic and slow to converge. Simulation results which verify the theoretical procedure are given.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: AD-A222639 , ESD-TR-90-048 , IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 38; 394-399
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 9
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    Plane waves and structures in turbulent channel flow (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A direct simulation of turbulent flow in a channel is analyzed by the method of empirical eigenfunctions (Karhunen-Loeve procedure, proper orthogonal decomposition). This analysis reveals the presence of propagating plane waves in the turbulent flow. The velocity of propagation is determined by the flow velocity at the location of maximal Reynolds stress. The analysis further suggests that the interaction of these waves appears to be essential to the local production of turbulence via bursting or sweeping events in the turbulent boundary layer, with the additional suggestion that the fast acting plane waves act as triggers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 2217-222
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 10
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    Improved approximations for control augmented structural synthesis (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A methodology for control-augmented structural synthesis is presented for structure-control systems which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a noncollocated direct output feedback control system. Truss areas, beam cross sectional dimensions, nonstructural masses and rotary inertias, and controller position and velocity gains are treated simultaneously as design variables. The structural mass and a control-system performance index can be minimized simultaneously, with design constraints placed on static stresses and displacements, dynamic harmonic displacements and forces, structural frequencies, and closed-loop eigenvalues and damping ratios. Intermediate design-variable and response-quantity concepts are used to generate new approximations for displacements and actuator forces under harmonic dynamic loads and for system complex eigenvalues. This improves the overall efficiency of the procedure by reducing the number of complete analyses required for convergence. Numerical results which illustrate the effectiveness of the method are given.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA PAPER 90-1060 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 02, 1990 - Apr 04, 1990; Long Beach, CA; United States
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
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