Constrained Layer Damping Treatments for Microstructures

2002 ◽  
Vol 124 (4) ◽  
pp. 612-616 ◽  
Author(s):  
Yi-Chu Hsu ◽  
I. Y. Shen
Keyword(s):  
Laser Doppler Vibrometer ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Element Analysis ◽  
Resonance Modes ◽  
Thick Photoresist ◽  
Measured Frequency Response ◽  
Damping Treatments ◽  
Base Structure ◽  
Silicon Beams

This paper presents a bulk micromachining process to fabricate micro-constrained layer treatments (MCLT) on a microstructure to increase its damping, and demonstrates the damping improvement through calibrated experiments. MCLT consists of a silicon base structure (e.g., beams or plates), a viscoelastic photoresist layer, and an aluminum constraining layer. Silicon base beams and plates are fabricated from {100} wafer through Ethylene-Diamine-Pyrocatechol etch and buffered oxide etch. A 4.5-μm thick photoresist AZ4620 is spun on the silicon base beam as the viscoelastic layer. Finally, an aluminum layer is deposited through low-pressure vapor deposition as the constraining layer. To evaluate damping performance of MCLT, silicon beams with and without MCLT are subjected to swept-sine excitations by PZT from 0 to 100 kHz. In addition, a laser Doppler vibrometer and a spectrum analyzer measured frequency response functions (FRF) of the specimen. A finite element analysis identifies the resonance modes measured in FRF. Experimental results confirm that MCLT can increase damping of silicon beams by at least 40%. Significantly better damping performance is expected, if the loss factor of the viscoelastic layer is increased.

Experimental and Finite Element Analysis of Stand-Off Layer Damping Treatments for Beams

2007 ◽  
Author(s):  
Jessica M. H. Yellin ◽  
I. Y. Shen ◽  
Per G. Reinhall
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Frequency Response ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Response Functions ◽  
Element Analysis ◽  
Frequency Response Functions ◽  
Damping Treatments ◽  
Passive Constrained Layer Damping

Passive stand-off layer (PSOL) and slotted stand-off layer (SSOL) damping treatments are presently being implemented in many commercial and defense designs. In a PSOL damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment. In an SSOL damping treatment, slots are included in the stand-off layer. A set of experiments using PSOL and SSOL beams in which the geometric properties of the stand-off layer were varied was conducted to analyze the contribution of the stand-off layer to the overall system damping. This set of experiments measured the frequency response functions for a series of beams in which the total slotted area of the stand-off layer was held constant while the number of slots in the stand-off layer was increased for a constant stand-off layer material. Finite element analysis models were developed in ANSYS to compare the predicted frequency response functions with the experimentally measured frequency response functions for the beams treated with PSOL and SSOL damping treatments. In these beams, the bonding layers used to fabricate these treatments were found to have a measurable and significant effect on the frequency response of the structure. The finite element model presented here thus included an epoxy layer between the base beam and the stand-off layer, a contact cement layer between the stand-off layer and the viscoelastic layer, and a method for modeling delamination.

Vibration Analyses of Cylindrical Hybrid Panel with Viscoelastic Layer Based on Layerwise Finite Elements

2006 ◽  
Vol 324-325 ◽  
pp. 699-702 ◽  
Author(s):  
Il Kwon Oh ◽  
Tai Hong Cheng
Keyword(s):  
Finite Element ◽  
Virtual Work ◽  
Structural Parameters ◽  
Element Model ◽  
Viscoelastic Layer ◽  
Normal Strain ◽  
Constrained Layer Damping ◽  
Damping Characteristics ◽  
Viscoelastic Layers ◽  
Damping Treatments

Based on full layerwise displacement shell theory, the vibration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modeling. The layerwise finite element model is formulated by using Hamilton’s virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factor and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

Dynamic Analysis to Evaluate Viscoelastic Passive Damping Augmentation for the Space Shuttle Remote Manipulator System

1992 ◽  
Vol 114 (3) ◽  
pp. 468-475 ◽  
Author(s):  
Thomas E. Alberts ◽  
Houchun Xia ◽  
Yung Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Active Control ◽  
Space Shuttle ◽  
Viscoelastic Layer ◽  
Passive Damping ◽  
Element Analysis ◽  
Joint Flexibility ◽  
Damping Treatments

This paper presents a NASTRAN finite element analysis for evaluation of the effectiveness of viscoelastic damping treatments as passive controls for large flexible space manipulators. The passive damping could be used alone or as an augmentation to active control. Perhaps the best existing example of a practical flexible manipulator is the space shuttle Remote Manipulator System (RMS). The authors use the RMS as an example for this investigation, subjecting it to a detailed dynamic analysis which can be used to evaluate the critical modes for control and to distinguish the modes which are good candidates for active control from those which are well suited for passive control. Modal potential energy analysis (MPE) is used to examine the modal energy distribution in each structural member of the complex flexible chained system. The results indicate that the most dominant contributors to end-point oscillations fall into two categories. These include very low frequency modes due to joint flexibility and higher frequency modes due to bending in the booms. Significant end-point motions result from each category, but the most significant motions are associated with joint flexibility. Finally, a finite element analysis is performed to evaluate the effectiveness of constrained viscoelastic layer damping treatments for passive vibration control. Passive damping augmentation is introduced through the use of a constrained viscoelastic layer damping treatment applied to the surface of the manipulator’s flexible booms. It is shown that even the joint compliance dominated modes can be damped to some degree through appropriate design of the treatment.

scholarly journals Dimensionless Analysis of Segmented Constrained Layer Damping Treatments with Modal Strain Energy Method

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Shitao Tian ◽  
Zhenbang Xu ◽  
Qingwen Wu ◽  
Chao Qin
Keyword(s):  
Shear Strain ◽  
Strain Field ◽  
Strain Energy ◽  
Design Parameters ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Modal Strain Energy ◽  
Modal Strain Energy Method ◽  
Damping Treatments ◽  
Strain Energy Method

Constrained layer damping treatments promise to be an effective method to control vibration in flexible structures. Cutting both the constraining layer and the viscoelastic layer, which leads to segmentation, increases the damping efficiency. However, this approach is not always effective. A parametric study was carried out using modal strain energy method to explore interaction between segmentation and design parameters, including geometry parameters and material properties. A finite element model capable of handling treatments with extremely thin viscoelastic layer was developed based on interlaminar continuous shear stress theories. Using the developed method, influence of placing cuts and change in design parameters on the shear strain field inside the viscoelastic layer was analyzed, since most design parameters act on the damping efficiency through their influence on the shear strain field. Furthermore, optimal cut arrangements were obtained by adopting a genetic algorithm. Subject to a weight limitation, symmetric and asymmetric configurations were compared. It was shown that symmetric configurations always presented higher damping. Segmentation was found to be suitable for treatments with relatively thin viscoelastic layer. Provided that optimal viscoelastic layer thickness was selected, placing cuts would only be applicable to treatments with low shear strain level inside the viscoelastic layer.

Modal Loss Factor Predication in Flexible Mechanism Systems With Constrain Viscoelastic Layers

1998 ◽  
Author(s):  
Zhang Xianmin ◽  
Liu Jike
Keyword(s):  
Equations Of Motion ◽  
Sandwich Beam ◽  
Viscoelastic Layer ◽  
Treatment Technique ◽  
Constrained Layer Damping ◽  
Modal Strain Energy ◽  
Frame Element ◽  
Modal Damping ◽  
Flexible Mechanism ◽  
Viscoelastic Layers

Abstract Control of dynamic vibration is critical to the operational success of many flexible mechanism systems. This paper addresses the problem of vibration control of such mechanisms through passive damping, using constrained layer damping treatment technique. A new type of shape function for three layer frame element containing a viscoelastic layer is developed. The equations of motion of the damped flexible mechanism are derived. Modal loss factors of this kind mechanisms are predicated from undamped normal mode by means of the modal strain energy method. Comparisons between the results obtained by this paper and the results obtained by exact solution of the governing equations for a well known sandwich beam demonstrate that the method presented in this paper is correct and reliable. Application of this method in predication of modal damping ratios for damped mechanisms is discussed. It is believed that the method of this paper hold the greatest potential for optimal design of damped flexible mechanism systems.

Some Pitfalls of Simplified Modeling for Viscoelastic Sandwich Beams

2000 ◽  
Vol 122 (4) ◽  
pp. 434-439 ◽  
Author(s):  
Eric M. Austin ◽  
Daniel J. Inman
Keyword(s):  
Strain Energy ◽  
Large Range ◽  
Sandwich Beams ◽  
Constrained Layer Damping ◽  
Modal Strain Energy ◽  
Skew Distributions ◽  
Transverse Vibrations ◽  
Simplified Modeling ◽  
Damping Treatments

It is commonplace in academia to base models of constrained-layer damping treatments on the assumption that the facesheets displace identically during transverse vibrations. This assumption is valid for a large range of problems, particularly for problems common in the era when damping was achieved by applying foil-backed treatments to thin panels. The authors show using a very simple example that oversimplified modeling can skew distributions of modal strain energy, a common indicator of damping. [S0739-3717(00)00204-X]

Thickness Deformation of Constrained Layer Damping: An Experimental and Theoretical Evaluation

2000 ◽  
Vol 123 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Peter Y. H. Huang ◽  
Per G. Reinhall ◽  
I. Y. Shen ◽  
Jessica M. Yellin
Keyword(s):  
Mathematical Model ◽  
Transfer Functions ◽  
Viscoelastic Layer ◽  
Experimental Setup ◽  
Experimental Measurements ◽  
Constrained Layer Damping ◽  
Response Functions ◽  
Theoretical Evaluation ◽  
Calculated Frequency ◽  
Direct Measurements

This paper presents a study of thickness deformation of the viscoelastic material in constrained layer damping (CLD) treatments. The first goal of the study is to demonstrate the feasibility of using direct measurement to investigate thickness deformation in CLD treatments. The experimental setup consisted of a constrained layer beam cantilevered to a shaker, an accelerometer mounted at the cantilevered end, and two laser vibrometers that simultaneously measured the responses of the base beam and the constraining layer, respectively, at the free end. A spectrum analyzer calculated frequency response functions (FRFs) between the accelerometer inputs and the vibrometer outputs. Measured FRFs of the base beam and the constraining layer were compared to detect thickness deformation. Experimental results showed that direct measurements can detect thickness deformation as low as 0.5 percent. The second goal is to evaluate the accuracy of a mathematical model developed by Miles and Reinhall [7] that accounts for thickness deformation. FRFs were calculated by using the method of distributed transfer functions by Yang and Tan [13]. Comparison of the numerical results with the experimental measurements indicated that consideration of thickness deformation can improve the accuracy of existing constrained layer damping models when the viscoelastic layer is thick.

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