Control of Sound Radiation of an Active Constrained Layer Damping Plate/Cavity System Using the Structural Intensity Approach

2002 ◽  
Vol 8 (6) ◽  
pp. 903-918 ◽  
Author(s):  
Mohamed S. Azzouz ◽  
J. Ro
Keyword(s):  
Smart Materials ◽  
Passive Control ◽  
Sound Radiation ◽  
Constrained Layer Damping ◽  
Acoustic Cavity ◽  
Structural Intensity ◽  
Vibrating Plates ◽  
Active Constrained Layer Damping ◽  
Cavity System ◽  
Active Constrained Layer

Considerable attention has been devoted to actively and passively controlling the sound radiation from vibrating plates into closed cavities. With the advent of smart materials, extensive effort has been exerted to control the vibration and sound radiation from flexible plates using smart sensors/actuators. The Active Constrained Layer Damping (ACLD) treatment has been used successfully for controlling the vibration of various flexible structures. The treatment provides an effective means for augmenting the simplicity and reliability of passive damping with the low weight and high efficiency of active controls to attain high damping characteristics over broad frequency bands. This study investigates a numerically simulated example consisting of an ACLD treated plate/acoustic cavity system excited by a point harmonic force. In this study, an ACLD treated plate/acoustic cavity coupled finite element model is utilized to calculate the structural intensity and sound pressure radiated by the vibrating plates. In the passive control, the optimum placement of ACLD patches is determined by the structural intensity of ACLD treated plates and compared to the results obtained by using the strain energy approach. The influence on the structural intensity of the plate due to the damping treatment is investigated.

Active Control of Vibration and Noise Radiation from Fluid-Loaded Cylinder using Active Constrained Layer Damping

2002 ◽  
Vol 8 (6) ◽  
pp. 877-902 ◽  
Author(s):  
W. Laplante ◽  
T. Chen ◽  
A. Baz ◽  
W. Sheilds
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Acoustic Radiation ◽  
Sound Radiation ◽  
Element Model ◽  
Water Tank ◽  
Constrained Layer Damping ◽  
Active Constrained Layer Damping ◽  
Active Constrained Layer ◽  
Surrounding Fluid

Vibration and sound radiation from fluid-loaded cylindrical shells are controlled using patches of Active Constrained Layer Damping (ACLD). The performance and the enhanced damping characteristics via reduced vibrations and sound radiation in the surrounding fluid is demonstrated both theoretically and experimentally. A prime motivation for this work is the potential wide applications in submarines and torpedoes where acoustic stealth is critical to the effectiveness of missions. A finite element model is also developed to predict the vibration and the acoustic radiation in the surrounding fluid of the ACLD-treated cylinders. The developed model is used to study the effectiveness of the control and placement strategies of the ACLD in controlling the fluid-structure interactions. A water tank is constructed that incorporates test cylinders treated with two ACLD patches placed for targeting specific vibration modes. Using this arrangement, the effectiveness of different control strategies is studied when the submerged cylinders are subjected to internal excitation, and the radiated sound pressure level in the water is observed. Comparisons are made between the experimental results and the theoretical predictions to validate the finite element model.

Passive Control of the Vibration and Sound Radiation from Submerged Shells

2002 ◽  
Vol 8 (4) ◽  
pp. 425-445 ◽  
Author(s):  
J. Oh ◽  
M. Ruzzene ◽  
A. Baz
Keyword(s):  
Smart Materials ◽  
Passive Control ◽  
Sound Radiation ◽  
Structural Vibration ◽  
Finite Element Models ◽  
Constrained Layer Damping ◽  
Noise Radiation ◽  
Experimental Validations ◽  
Vibration And Sound Radiation ◽  
Passive Constrained Layer Damping

Vibration and noise radiation from fluid-loaded cylindrical shells are controlled using multiple stiffeners and Passive Constrained Layer Damping treatment. Dynamic and fluid finite element models are developed to study the fundamental phenomena governing the interaction between the stiffened shell, with and without damping, and the fluid domain surrounding it. The models are used to predict the response of the shell and to evaluate the effect of the stiffening rings and damping treatment on both the structural vibration and noise radiation in the fluid domain. The prediction of the models are validated experimentally and against the predictions of a commercial FE software package (ANSYS). It is shown that stiffening of the shell reduces the amplitude of the vibration and noise radiation, particularly for high order lobar modes. The attenuation of the shell response and sound radiation can be significantly increased through the application of Passive Constrained Layer Damping treatment on the inner surface of the stiffening rings. The numerical and experimental validations demonstrate the accuracy of the developed models and emphasize its potential extension to the application of smart materials for active control of vibration and noise radiation from fluid-loaded shells.

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