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  • 1
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    Identification of structural parameters from helicopter dynamic test data (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method is presented for obtaining the mass, stiffness, and damping parameters of a linear mathematical model, having fewer degrees of freedom than the structure it represents, directly from dynamic response measurements on the actual helicopter without a priori knowledge of the physical characteristics of the fuselage. The only input information required in the formulation is the approximate natural frequency of each mode and mobility data measured proximate to these frequencies with sinusoidal force excitation applied at only one point on the vehicle. The practicality and numerical soundness of the theoretical development was demonstrated through a computer simulation of an experimental program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 239-248
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Application of antiresonance theory to helicopters (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Antiresonance theory is the principle underlying nonresonant nodes in a structure, and covers both nonresonant nodes occurring naturally and those introduced by devices such as dynamic absorbers and antiresonant isolators. The dynamic antiresonant vibration isolator (DAVI) and the nodale module are examples of the applications of transfer antiresonances. It is shown that antiresonances are eigenvalues, and that they can be determined by matrix iteration. Applications of antiresonance theory to helicopter engineering problems, using the antiresonant eigenvalue equation are suggested.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 101-106
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Analytical research on a synchronous gyroscopic vibration absorber (1965)
    In:  CASI
    Details
    Publication Date: 2019-05-29
    Description: Synchronous gyroscopic vibration absorber
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-338
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Rotor dynamic simulation and system identification methods for application to vacuum whirl data (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods of using rotor vacuum whirl data to improve the ability to model helicopter rotors were developed. The work consisted of the formulation of the equations of motion of elastic blades on a hub using a Galerkin method; the development of a general computer program for simulation of these equations; the study and implementation of a procedure for determining physical parameters based on measured data; and the application of a method for computing the normal modes and natural frequencies based on test data.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-159356 , NAS 1.26:159356 , R-1496
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Study of incomplete models of dynamic structures (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Incomplete models of dynamic structures
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-109630 , R-826
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    The theory of incomplete models of dynamic structures (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Limited frequency range analytical model for predicting mass and stiffness changes effect on natural frequencies and normal modes
    Keywords: STRUCTURAL MECHANICS
    Type: MATERIALS AND STRUCTURAL DYNAMICS, AMERICAN INST. OF AERONAUTICS AND ASTRONAUTICS AND AMERICAN SOCIETY OF MECHANICAL ENGINEERS, STRUCTURES, STRUCTURAL DYNAMICS, AND MATERIALS CONFERENCE, 11TH; Apr 22, 1970 - Apr 24, 1970; DENVER, CO
    Format: text
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  • 7
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    Analytical testing (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Analytical methods for combining flight acceleration and strain data with shake test mobility data to predict the effects of structural changes on flight vibrations and strains are presented. This integration of structural dynamic analysis with flight performance is referred to as analytical testing. The objective of this methodology is to analytically estimate the results of flight testing contemplated structural changes with minimum flying and change trials. The category of changes to the aircraft includes mass, stiffness, absorbers, isolators, and active suppressors. Examples of applying the analytical testing methodology using flight test and shake test data measured on an AH-1G helicopter are included. The techniques and procedures for vibration testing and modal analysis are also described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-3429 , R-1614
    Format: application/pdf
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