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  • Other Sources  (277)
  • STRUCTURAL MECHANICS  (277)
  • 1980-1984  (277)
  • 1983  (277)
  • 1
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    Measurement of the inertial constants of a rigid or flexible structure of arbitrary share through a vibration test (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The inertial constants of an aircraft rocket, or of any other structure, are defined without materializing any rotating axis. The necessary equipment is very similar to that used normally for ground vibration tests. An elastic suspension is used to obtain the total natural modes corresponding to the motions of the structure as a solid. From the measurements of the generalized masses of these modes it is possible to compute the inertial constants: (1) center of inertia; (2) tensor of inertia; and (3) mass. When the structure is not strictly rigid a purification process, based on the mean square method makes it possible to rigidify it at the price of some approximations and a few more measurements. Eventual additional masses, that are not parts of the structure, can be taken into account.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-77557 , NAS 1.15:77557
    Format: application/pdf
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  • 2
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    The NASTRAN user's manual (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: All information directly associated with problem solving using the NASTRAN program is presented. This structural analysis program uses the finite element approach to structural modeling wherein the distributed finite properties of a structure are represented by a finite element of structural elements which are interconnected at a finite number of grid points, to which loads are applied and for which displacements are calculated. Procedures are described for defining and loading a structural model. Functional references for every card used for structural modeling, the NASTRAN data deck and control cards, problem solution sequences (rigid formats), using the plotting capability, writing a direct matrix abstraction program, and diagnostic messages are explained. A dictionary of mnemonics, acronyms, phrases, and other commonly used NASTRAN terms is included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-SP-222(06) , NAS 1.12/6:222(06)
    Format: application/pdf
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  • 3
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    Bending Stiffness of Multiwall Sandwich (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: An analytical and experimental study was carried out to understand the extensional and flexural behavior of multiwall sandwich, a metallic insulation composed of alternate layers of flat and dimpled foil. The multiwall sandwich was structurally analyzed by using several simplifying assumptions combined with a finite element analysis. The simplifying assumptions made in this analysis were evaluated by bending and tensile tests. Test results validate the assumption that flat sheets in compression do not significantly contribute to the flexural stiffness of multiwall sandwich for the multiwall geometry tested. However, calculations show that thicker flat sheets may contribute significantly to bending stiffness and cannot be ignored. Results of this analytical approach compare well with test data; both show that the extensional stiffness of the dimpled sheet in he 0 deg direction is about 30 percent of that for a flat sheet, and that in the 45 deg direction, it is about 10 percent. The analytical and experimental multiwall bending stiffness showed good agreement for the particular geometry tested.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-84613 , L-15549 , NAS 1.15:84613
    Format: application/pdf
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  • 4
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    Flutter analysis of a transport wing using XTRAN3S (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: As part of the continuing process of evaluating and validating the XTRAN3S unsteady transonic aerodynamic computer program, the code has been applied to the flutter analysis of a transport type wing. The configuration analyzed was an aspect ratio 8 wing with a taper ratio of 0.4, a quarter chord sweep of 20 degrees and a NACA 65A-012 airfoil section. The analytical results compare well with the experimental flutter boundary and exhibit the classical 'transonic dip'. A literature search of available transport wing transonic flutter data is included.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 83-0922 , Structures, Structural Dynamics and Materials Conference; May 02, 1983 - May 04, 1983; Lake Tahoe, NV
    Format: text
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  • 5
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    A refined finite element for vibration analysis of twisted blades based on beam theory (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A finite element method of discretizing beam segments of pretwisted rotating blades is presented. Employing the matrix displacement method, stiffness and mass properties are developed from basic mechanics of a pretwisted beam theory. By introducing the proper displacement functions, the effect of rotor blade rotational motion on the stiffness matrix is obtained systematically from the kinetic energy expression. Comparing with other beam elements the derivation of this element is more fundamental. This allows one to apply the same approach to more complicated problems including nonlinear effects or complex dynamic motions. Illustrative examples are given comparing numerical results with available data and other numerical solutions from rotating and nonrotating force fields. These examples show that accurate prediction of vibration frequencies for pretwisted blades can be obtained by employing a quite modest number of degrees of freedom.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 83-0917 , Structures, Structural Dynamics and Materials Conference; May 02, 1983 - May 04, 1983; Lake Tahoe, NV
    Format: text
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  • 6
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    Friction damping studies in multiple turbine blade systems by lumped mass method (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Analytical studies were conducted on multiple turbine blade systems using the lumped mass method. Each blade was idealized by a two mass-two spring model whose modal values were determined from the known frequencies corresponding to the first two bending modes and the frequency corresponding to the platform lockup condition. Two friction damping models were considered namely, the blade-to-blade and the blade-damper-blade. The equations of motion derived on the basis of these models were solved by a method of harmonic balance, assuming, in effect, that under cyclic excitation the blades will exhibit cyclic response at the same frequency. The solutions for 8 blade, 16 blade, and 4 blade systems were obtained using the computer program BLADE. The levels of damping produced by the two friction damping models were compared and evaluated. The optimal values of the friction force, for which the tip amplitude of the blades had a minimum value, were determined.
    Keywords: STRUCTURAL MECHANICS
    Type: Annual Mini-Symposium on Aerospace Science and Technology; Mar 22, 1983; Wright-Patterson AFB, OH
    Format: text
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  • 7
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    Effects of structural coupling on mistuned cascade flutter and response (1983)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effects of structural coupling on mistuned cascade flutter and response are analytically investigated using an extended typical section model. This model includes both structural and aerodynamic coupling between the blades. The model assumes that the structurally coupled system natural modes were determined and are represented in the form of N bending and N torsional uncoupled modes for each blade, where N is the number of blades and, hence, is only valid for blade dominated motion. The aerodynamic loads are calculated by using two dimensional unsteady cascade theories in the subsonic and supersonic flow regimes. The results show that the addition of structural coupling can affect both the aeroelastic stability and frequency. The stability is significantly affected only when the system is mistuned. The resonant frequencies can be significantly changed by structural coupling in both tuned and mistuned systems, however, the peak response is significantly affected only in the latter.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-83049 , E-1500 , NAS 1.15:83049 , Ann. Intern. Gas Turbine Conf.; Mar 27, 1983 - Mar 31, 1983; Phoenix, AZ; United States
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  • 8
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    Tire Modeling (1983)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The workshop was organized into six sessions dealing with finite element developments, applications to tire dynamic problems, solution techniques for tire contact problems, experimental data, tire thermal studies, and current design practices.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CP-2264 , L-15578 , NAS 1.55:2264 , Sep 07, 1982 - Sep 09, 1982; Hampton, VA; United States
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  • 9
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    Algorithms for real-time flutter identification (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The work reported here addresses the important algorithm issues necessary to achieve a real-time flutter monitoring system; namely, the guidelines for choosing appropriate model forms, reduction of the parameter convergence transient, handling multiple modes, the effect of overparameterization, and estimate accuracy predictions, both online and for experiment design. An approach for efficiently computing continuous-time flutter parameter Cramer-Rao estimate error bounds has been developed. This enables a convincing comparison of theoretical and simulation results, as well as off-line studies in preparation for a flight test. Theoretical predictions, simulation and flight test results from the NASA/Dryden Drones for Aerodynamic and Structural Test (DAST) Program are compared.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 83-2223 , Guidance and Control Conference; Aug 15, 1983 - Aug 17, 1983; Gatlinburg, TN
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  • 10
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    Application of a systematic finite-element model modification technique to dynamic analysis of structures (1983)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For abstract see A82-30178.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-83292 , NAS 1.15:83292 , AIAA/ASME/ASCE/AHS Structures, Structural Dyn. and Mater. Conf.; May 10, 1982 - May 12, 1982; New Orleans
    Format: application/pdf
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