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  • 1
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    Simultaneous active control of flexural and extensional waves in beams (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The simultaneous active control of flexural and extensional vibrations in elastic beams is experimentally investigated. The results demonstrate that using pairs of piezoceramic transducers, whose elements are symmetrically located and independently controlled by a multichannel adaptive controller, enables the high attenuation of both flexural and extensional response. This capability is due to the nature of the piezoceramic element, which when bonded to the surface of the structure and electrically excited, exerts a surface strain on the structure. This strain enables input of both shear forces and moments into the structural system. The results are applicable to many situations where extensional vibrations couple to large flexural vibrations and subsequently radiate significant sound levels.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Intelligent Material Systems and Structures (ISSN 1045-389X); 1; 235-247
    Format: text
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  • 2
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    The input mobility of an infinite circular cylindrical elastic shell filled with fluid (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The force input mobility of an infinite elastic circular cylindrical shell filled with fluid is derived by using the spectral equations of motion. Mobilities are evaluated and their physical interpretations are discussed for a steel shell of thickness h/a = 0.05 filled with water and vibrating in the n = 0, 1 and 2 circumferential modes. The results are subsequently used to analyze the related situations of wave transmission through a radial ring constraint and the far field vibrational energy distributions between the contained fluid and the shell wall for line and point driving forces.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 87; 409-427
    Format: text
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  • 3
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    Monopole excitation of vibrations in an infinite cylindrical elastic shell filled with fluid (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The vibrations of a cylindrical elastic shell filled with fluid and excited by a monopole acoustic source are studied. The modal mobilities of the shell wall at the source plane are examined for different radial locations of the source. The distribution of vibrational energy between the shell and the fluid field is calculated at various axial locations along the shell and for different radial source locations. An interchange of energy of vibration between the shell and the fluid as the wave field propagates along the shell-fluid system is observed.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 96; 101-110
    Format: text
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  • 4
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    Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.
    Keywords: STRUCTURAL MECHANICS
    Format: application/pdf
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  • 5
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    Plane thermoelastic deformation of internally heated annular disks or hollow cylinders (1966)
    In:  CASI
    Details
    Publication Date: 2019-05-29
    Description: Plane thermoelastic deformation of internally heat annular plates and hollow cylinders - structural dynamics
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TR-R-229
    Format: application/pdf
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  • 6
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    Assessment of space vehicle aeroacoustic- vibration prediction, design, and testing (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Space vehicle structural vibration induced by acoustic and aerodynamic noise
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-1596
    Format: application/pdf
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  • 7
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    Experiments on active control of vibrational power flow using piezoceramic actuators/sensors (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 30; 457-463
    Format: text
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  • 8
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    The effect of source location on the structural-acoustic interaction of an infinite elastic shell (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper deals with the response of an infinite elastic shell to simple acoustic sources (monopole and dipole). This simplified model is considered in order to gain insight into the characteristics of aircraft interior noise. The shell represents the aircraft fuselage and the sources are due to the propellor. Specifically, in this study the location of the source with respect to the cylinder is the major concern. How this affects acoustic line power, intensity flow into the shell and internal sound pressure is analyzed.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 85-0788 , Structures, Structural Dynamics, and Materials Conference; Apr 15, 1985 - Apr 17, 1985; Orlando, FL
    Format: text
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  • 9
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    Active vibration isolation using smart structures (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Passive technologies for the isolation of structures from vibrating sources are often inadequate. Using active control inputs applied directly to the source or designing a structure integrating the transducers required for the control inputs and the response measurements are ways of dealing with the problem. Results are given which were obtained on an experimental set up simulating this kind of problem where the form and the position of the transducers could be varied. By measuring the response of the structure integrated over a particular area the effects of particular types of modes could be taken into account to deal with specific types of input or limit particular modes of response more efficiently. Results of using different modes of vibration excitation of the receiving structure with and without control are presented for particular input frequencies. The problems of optimizing the control system to deal with multiple frequency inputs are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: 1991 American Control Conference; Jun 26, 1991 - Jun 28, 1991; Boston, MA; United States
    Format: text
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  • 10
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    Active isolation of vibrations with adaptive structures (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Vibration transmission in structures is controlled by means of a technique which employs distributed arrays of piezoelectric transducers bonded to the supporting structure. Distributed PVDF piezoelectric strips are employed as error sensors, and a two-channel feedforward adaptive LMS algorithm is used for minimizing error signals and thereby controlling the structure. A harmonic force input excites a thick plate, and a receiving plate is configured with three pairs of piezoelectric actuators. Modal analyses are performed to determine the resonant frequencies of the system, and a scanning laser vibrometer is used to study the shape of the response of the receiving plate during excitation with and without the control algorithm. Efficient active isolation of the vibrations is achieved with modal suppression, and good control is noted in the on-resonance cases in which increased numbers of PVDF sensors and piezoelectric actuators are employed.
    Keywords: STRUCTURAL MECHANICS
    Type: NOISE-CON 91: National Conference on Noise Control Engineering; Jul 14, 1991 - Jul 16, 1991; Tarrytown, NY; United States
    Format: text
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