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  • Other Sources  (465)
  • STRUCTURAL MECHANICS  (465)
  • 2020-2024
  • 1985-1989  (465)
  • 1989  (465)
  • 1
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    Mixed finite element models for free vibrations of thin-walled beams (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Simple, mixed finite element models are developed for the free vibration analysis of curved thin-walled beams with arbitrary open cross section. The analytical formulation is based on a Vlasov's type thin-walled beam theory with the effects of flexural-torsional coupling, transverse shear deformation and rotary inertia included. The fundamental unknowns consist of seven internal forces and seven generalized displacements of the beam. The element characteristic arrays are obtained by using a perturbed Lagrangian-mixed variational principle. Only C(sup o) continuity is required for the generalized displacements. The internal forces and the Lagrange multiplier are allowed to be discontinuous at interelement boundaries. Numerical results are presented to demonstrate the high accuracy and effectiveness of the elements developed. The standard of comparison is taken to be the solutions obtained by using 2-D plate/shell models for the beams.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-2868 , L-16506 , NAS 1.60:2868
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Overview of the NASA program in computational structural mechanics (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: In order to meet the anticipated needs in modeling and analysis of advanced aerospace structures, NASA has developed a program focused on computational structural mechanics. The objective of this program is to advance the state-of-the-art in computational analysis to make accurate analysis of very large and complex structural problems routine. This will be accomplished by emphasizing two key areas: (1) the development of advanced analytical methods, extending beyond traditional approaches and, (2) the exploitation of the newest and most powerful parallel/multiprocessor computers available. Computational testbeds will be developed to serve as technology integrators and to promote/accelerate methodology research and development. An additional, and highly desirable, effect of the Computational Structural Mechanics (CSM) program would be to influence the design of future hardware and software systems to reflect the needs of structural analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center, NASA Workshop on Computational Structural Mechanics 1987, Part 1; p 1-23
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    The 23rd Aerospace Mechanisms Symposium (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Technological areas covered include space lubrication, bearings, aerodynamic devices, spacecraft latches, deployment, positioning, and pointing. Devices for Space Station docking and manipulator and teleoperator mechanisms are also described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CP-3032 , M-611 , NAS 1.55:3032 , May 03, 1989 - May 05, 1989; Huntsville, AL; United States
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  • 4
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    Characterization of structural connections using free and forced response test data (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The accurate prediction of system dynamic response often has been limited by deficiencies in existing capabilities to characterize connections adequately. Connections between structural components often are complex mechanically, and difficult to accurately model analytically. Improved analytical models for connections are needed to improve system dynamic predictions. A procedure for identifying physical connection properties from free and forced response test data is developed, then verified utilizing a system having both a linear and nonlinear connection. Connection properties are computed in terms of physical parameters so that the physical characteristics of the connections can better be understood, in addition to providing improved input for the system model. The identification procedure is applicable to multi-degree of freedom systems, and does not require that the test data be measured directly at the connection locations.
    Keywords: STRUCTURAL MECHANICS
    Type: Biennial ASME Conference on Mechanical Vibration and Noise; Sept. 17-21, 1989; Montreal; Canada
    Format: text
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  • 5
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    Microstructural non-uniformity as related to unidirectional compression performance (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The compression performance of unidirectional composite laminates (UDCLs) is related not only to intrinsic or local strength, but also to a sample's ability to resist propagaton of initial damage. This paper introduces a simple shear lag model which is applied to a compression loaded UDCL with initial damage. Among the information obtained are axial overload and matrix layer shear strain factors in the neighborhood of the damage zone. These factors indicate that propagation may occur with relatively little initial damage and emphasize the need for a more complete understanding of compression behavior than currently exists.
    Keywords: STRUCTURAL MECHANICS
    Type: International SAMPE Technical Conference; Sept. 25-28, 1989; Atlantic City, NJ; United States
    Format: text
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  • 6
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    On modelling the residual strength of impact damaged, compression loaded laminates (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A methodology is presented to predict the residual compression strength of impact damaged composite laminates by considering the competing failure modes of local delamination buckling and compression failure. The minimum delamination buckling load and the location of the first local region to buckle are determined by a Rayleigh-Ritz analysis. The Rayleigh-Ritz analysis is formulated to account for the multiple delamination locations, Poisson's ratio mismatch between sublaminates and possible bending-stretching coupling behavior of the delaminated regions. The compression failure load is determined by a modified maximum strain criterion applied in the delaminated region. The minimum delamination buckling and compression failure loads may be compared to the global buckling load to predict initial failure. For non-catastrophic failures, failure sequences are predicted in an iterative manner. Analytical predictions for sequential failure modes and loads are shown to correlate well with experimental results. A comparative evaluation of various delamination buckling models and their accuracy in predicting experimental results is also presented.
    Keywords: STRUCTURAL MECHANICS
    Type: International SAMPE Technical Conference; Sept. 25-28, 1989; Atlantic City, NJ; United States
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  • 7
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    A model for compression after impact strength evaluation (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: One key property commonly used for evaluating composite material performance is compression after impact strength (CAI). Standarad CAI tests typically use a specific laminate stacking sequence, coupon geometry, and impact level. In order to understand what material factors affect CAI, evaluation of test results should include more than comparisons of the measured strength for different materials. This study considers the effects of characteristic impact damage state, specimen geometry, material toughness, ply group thickness, undamaged strength, and failure mode. The results of parametric studies, using an analysis model developed to predict CAI, are discussed. Experimental results used to verify the model are also presented. Finally, recommended pre- and post-test CAI evaluation schemes which help link material behavior to structural performance are summarized.
    Keywords: STRUCTURAL MECHANICS
    Type: International SAMPE Technical Conference; Sept. 25-28, 1989; Atlantic City, NJ; United States
    Format: text
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  • 8
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    Variable geometry trusses (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Vibration control and kinematic control with variable-geometry trusses are covered. The analytical approach taken is to model each actuator with lumped masses and model a beam with finite elements, including in each model the generalized reaction forces from the beam on the actuator or vice versa. It is concluded that, from an operational standpoint, the variable-geometry truss actuator is more favorable than the inertia-type actuator. A spatial variable-geometry truss is used to test out rudimentary robotic tasks.
    Keywords: STRUCTURAL MECHANICS
    Type: U.S. Army Research Offoce Workshop on Smart Materials, Structures, and Mathematical Issues; Sept. 15-16, 1988; Blacksburg, VA; United States
    Format: text
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  • 9
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    Active control of buckling of flexible beams (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Mathematical models are presented that simulate the dynamic characteristics of shape memory alloy actuators made of nickel-titanium alloy (Nitinol) controlling the buckling of compressive structural members. A closed-loop computer-controlled system has been designed, based on the proposed mathematical models, and has been implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The results emphasized the importance of buckling control and suggest the potential of shape memory alloy actuators as attractive means for controlling structural deformation in a simple and reliable way.
    Keywords: STRUCTURAL MECHANICS
    Type: Biennial Conference on Failure Prevention and Reliability - 1989; Sept. 17-21, 1989; Montreal; Canada
    Format: text
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  • 10
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    Fiber optic strain measurements in filament-wound graphite-epoxy tubes containing embedded fibers (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Filament-wound graphite-epoxy tubes fabricated with embedded fiber optic sensors were tested at NASA Langley Research Center to evaluate the feasibility of monitoring stress with a fiber optic technique. Resistance strain gauges were attached to the tubes to measure strain at four locations along the tubes. Both static and dynamic strain measurements were made with an excellent agreement between the embedded fiber optic strain sensor and the strain gauges. The results indicate that fiber optic sensors embedded in composites may be useful as the sensing component of smart structures.
    Keywords: STRUCTURAL MECHANICS
    Type: Fiber Optic Smart Strutures and Skins; Sept. 8-9, 1988; Boston, MA; United States
    Format: text
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