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 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 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.

Damping Characteristics of Beams with Enhanced Self-Sensing Active Constrained Layer Treatments Under Various Boundary Conditions

2004 ◽  
Vol 127 (2) ◽  
pp. 173-187 ◽  
Author(s):  
J. X. Gao ◽  
W. H. Liao
Keyword(s):  
Boundary Conditions ◽  
Careful Analysis ◽  
Constrained Layer Damping ◽  
Various Boundary Conditions ◽  
Damping Characteristics ◽  
Control Gain ◽  
Active Constrained Layer Damping ◽  
Damping Treatments ◽  
Active Constrained Layer ◽  
Loss Factors

In this paper, an energy-based approach is developed to investigate damping characteristics of beams with enhanced self-sensing active constrained layer (ESACL) damping treatments. Analytical formulations for the active, passive, and total hybrid modal loss factors of the cantilever and simply-supported beams partially covered with the ESACL are derived. The analytical formulations are validated with the results in the literature and experimental data for the cantilever beam. Beams with other boundary conditions can also be solved and discussed using the presented approach. The results show that the edge elements in the ESACL can significantly improve the system damping performance as compared to the active constrained layer damping treatment. The effects of key parameters, such as control gain, edge element stiffness, location, and coverage of the ESACL patch on the system loss factors, have been investigated. It has also been shown that the boundary conditions play an important role on the damping characteristics of the beam structure with the ESACL treatment. With careful analysis on the location and coverage of the partially covered ESACL treatment, effective vibration control for beams under various boundary conditions for specific modes of interest would be achieved.

Modeling of Active Constrained Layer Damping Structures Using a Commercial Finite Element Code

2001 ◽  
Author(s):  
Arnold Lumsdaine
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Single Mode ◽  
Vibration Damping ◽  
Constrained Layer Damping ◽  
Finite Element Code ◽  
Passive Damping ◽  
Study Results ◽  
Active Constrained Layer Damping ◽  
Active Constrained Layer

Abstract Active Constrained Layer Damping (ACLD), involving a hybrid of active and passive damping elements, has been shown to be a promising method for maximizing vibration damping effectiveness. Active damping can be effective at reducing vibration of a given single mode. Passive damping has dissipative qualities for all modes. There has been much discussion comparing and contrasting the uses of these different methods in the literature. It has been found that using a hybrid ACLD layer can be more effective than just using an active control (AC) approach or a Passive Constrained Layer Damper (PCLD) approach, in some cases. ACLD structures are characterized in the literature either by the development of analytic equations, or by finite element modeling. In cases where the ACLD structure is modeled using finite elements, the formulation is done by the author in developing a code. This limits the availability of the result beyond a specific application. For the modeling of ACLD structures to be more generally applicable, and available, modeling could be done using a commercial finite element code. A greater variety of different structures could be modeled, and structural optimization could easily be integrated. The study of ACLD structures would be available to an audience without the resources to construct their own elements. To the author’s knowledge, no studies of ACLD structures exist using a generally available finite element code. The ABAQUS commercial finite element code, with certain customizations, is used in this study. Results compare favorably with other sources in the literature.

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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