Enhanced active constrained layer damping treatment with symmetrically and nonsymmetrically distributed edge elements

1998 ◽  
Author(s):  
Yanning Liu ◽  
Kon-Well Wang
Keyword(s):  
Constrained Layer Damping ◽  
Edge Elements ◽  
Active Constrained Layer Damping ◽  
Active Constrained Layer

Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements: Part II — System Analysis

1997 ◽  
Author(s):  
W. H. Liao ◽  
K. W. Wang
Keyword(s):  
System Analysis ◽  
Careful Analysis ◽  
Constrained Layer Damping ◽  
Passive Damping ◽  
Active System ◽  
Control Effort ◽  
Edge Elements ◽  
Active Constrained Layer Damping ◽  
Critical Edge ◽  
Active Constrained Layer

Abstract This paper presents some important characteristics of enhanced active constrained layer damping (EACL) treatments for vibration controls. Specific interests are on understanding how the edge elements will influence the active action authority, the passive damping ability, and their combined effects in EACL. Analysis results indicate that the edge elements can significantly improve the active action transmissibility of the current active constrained layer damping (ACL) treatment due to the bypass effect. Although the edge elements will slightly reduce the viscoelastic material (VEM) passive damping, the EACL will still have significant damping from the VEM. Combining the overall active and passive actions, the new EACL with sufficiently stiff edge elements not only could achieve better performance with less control effort compared to the current ACL system, but also could outperform the purely active system. With careful analysis, we can map out the required critical edge element stiffness for successful designs. In addition, analysis also shows that the EACL treatment is a more robust design. That is, it could outperform both the purely active and passive systems throughout a much broader design space than the current ACL configuration. With these desirable characteristics, the EACL could be used to realize an overall optimal active-passive hybrid system.

Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements, Part 1: Finite Element Model Development and Validation

1998 ◽  
Vol 120 (4) ◽  
pp. 886-893 ◽  
Author(s):  
W. H. Liao ◽  
K. W. Wang
Keyword(s):  
Finite Element ◽  
Model Development ◽  
Element Model ◽  
System Model ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Active System ◽  
Edge Elements ◽  
Active Constrained Layer Damping ◽  
Active Constrained Layer

This paper is concerned with the enhanced active constrained layer (EACL) damping treatment with edge elements. A finite element time-domain-based model (FEM) is developed for the beam structure with partially covered EACL. The edge elements are modeled as equivalent springs mounted at the boundaries of the piezoelectric layer. The Golla-Hughes-McTavish (GHM) method is used to model the viscoelastic layer. The GHM dissipation coordinates can describe the frequency-dependent viscoelastic material properties. This model becomes the current active constrained layer (ACL) system model as the stiffness of the edge elements approaches zero. Without the edge elements and viscoelastic materials, the purely active system model can also be obtained from the EACL model as a special case. Lab tests are conducted to validate the models. The frequency responses of the EACL, current ACL, and purely active systems predicted by the FEM match the test results closely. Utilizing these models, analysis results are illustrated and discussed in Part (2) of this paper.

Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements, Part 2: System Analysis

1998 ◽  
Vol 120 (4) ◽  
pp. 894-900 ◽  
Author(s):  
W. H. Liao ◽  
K. W. Wang
Keyword(s):  
System Analysis ◽  
Careful Analysis ◽  
Constrained Layer Damping ◽  
Passive Damping ◽  
Active System ◽  
Control Effort ◽  
Edge Elements ◽  
Active Constrained Layer Damping ◽  
Critical Edge ◽  
Active Constrained Layer

This paper presents some important characteristics of enhanced active constrained layer damping (EACL) treatments for vibration controls. Specific interests are on understanding how the edge elements will influence the active action authority, the passive damping ability, and their combined effects in EACL. Analysis results indicate that the edge elements can significantly improve the active action transmissibility of the current active constrained layer damping (ACL) treatment. Although the edge elements will slightly reduce the viscoelastic material (VEM) passive damping, the EACL will still have significant damping from the VEM. Combining the overall active and passive actions, the new EACL with sufficiently stiff edge elements not only could achieve better performance with less control effort compared to the current ACL system, but also could outperform the purely active system. With careful analysis, we can map out the required critical edge element stiffness for successful designs. In addition, analysis also shows that the EACL treatment is a more robust design. That is, it could outperform both the purely active and passive systems throughout a much broader design space than the current ACL configuration. With these desirable characteristics, the EACL could be used to realize an overall optimal active-passive hybrid system.

Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements: Part I — Finite Element Model Development and Validation

1997 ◽  
Author(s):  
W. H. Liao ◽  
K. W. Wang
Keyword(s):  
Finite Element ◽  
Model Development ◽  
Element Model ◽  
System Model ◽  
Constrained Layer Damping ◽  
Active System ◽  
Edge Elements ◽  
Active Constrained Layer Damping ◽  
Viscoelastic Modeling ◽  
Active Constrained Layer

Abstract This paper is concerned with the enhanced active constrained layer (EACL) damping treatment with edge elements. A finite element time-domain-based model (FEM) is developed for the beam structure with partially covered EACL. The edge elements are modeled as equivalent springs mounted at the boundaries of the piezoelectric layer. The transverse, axial, and shear motions are included. The energy method in combination with the Golla-Hughes-McTavish (GHM) viscoelastic modeling method is used. The GHM dissipation coordinates can describe the frequency-dependent viscoelastic material properties. This model becomes the current active constrained layer (ACL) system model as the stiffness of the edge elements approaches zero. Without the edge elements and viscoelastic materials, the purely active system model can also be obtained from the EACL model as a special case. Lab tests are conducted to validate the models. The frequency responses of the EACL, current ACL, and purely active systems predicted by the FEM match the test results closely. Utilizing these models, analysis results are illustrated and discussed in Part (II) of this paper.

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.

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