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1
Rongong, Jem Athing. "Shear and extensional behaviour of passive and active constrained layer damping." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269380.
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Chantalakhana, Chak. "Model-based control of plate vibrations using active constrained layer damping." Thesis, University of Sheffield, 2000. http://etheses.whiterose.ac.uk/14796/.
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In this thesis, the author presents a numerical and experimental study of the application of active constrained layer damping to a clamped-clamped plate. Piezoelectric actuators with modal controllers are used to improve the performance of vibration suppression from the passive constrained layer damping treatment. Surface damping treatments are often effective at suppressing higher frequency vibrations in thin-walled structures such as beams, plates and shells. However, the effective suppression of lower frequency modes usually requires the additional of an active vibration control scheme to augment the passive treatment. Advances in the technologies associated with so-called smart materials are dramatically reducing the cost, weight and complexity of active structural control and make it feasible to consider active schemes in an increasing number of applications. Specifically, a passive constrained layer damping treatment is enhanced with an active scheme employing a piezoceramic (PZT) patch as the actuator. Starting with an established finite element formulation it is shown how model updating and model reduction are required to produce a low-order state-space model which can be used as the basis for active control. The effectiveness of the formulation is then demonstrated in a numerical study. Finally, in the description of the experimental study it is shown how modes in the frequency range from 0 to 600 Hz are effectively suppressed: the two lowest modes (bending and torsional) through active control, the higher modes (around ten in number) by the passive constrained damping layer. The study'S original contribution lies in the experimental demonstration that given a sufficiently accurate model of the plate and passive constrained damping layer, together with a suitable active feedback control algorithm, spillover effects are not significant even when using a single sensor and single actuator. The experimental traces show, in some instances, minor effects due to spillover. However, it can be concluded that the presence of the passive layer introduces sufficient damping into the residual modes to avoid any major problems when using only the minimum amount of active control hardware.
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Koh, Byungjun. "Hybrid active-passive constrained layer damping treatments in beams, plates and shells." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/397336/.
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The basic concept of Hybrid Active-Passive Constrained Layer Damping (HAPCLD) treatment was proposed by introducing active control to the concept of passive constrained layer damping configuration in the 1990s to compensate for weak points in active and passive controls by using their respective merits for more robust and stable control. Since then, combinations of various configurations and applicable control strategies have been proposed and studied in many engineering areas. However, there is still a need for a new modelling method to more easily establish models of HAPCLD treatment and its validation through control analysis and experiment with various structures from beams to curved plates. In this thesis, velocity feedback control strategy was applied to cantilever beams with four different configurations of HAPCLD treatment to check their applicability. Moreover, the application was expanded to flat and curved plates. Control results with each configuration for flat and curved plates were analysed by using self-established MATLAB codes based on the Finite Element Method (FEM) with the basic concept of a layer-wise approach for coupling each layer of structures and deriving Equivalent Single Layer (ESL) models. This new numerical modelling method was established by introducing coupling matrices based on a layer-wise approach to combine individual FE mass and stiffness matrices of each layer into one ESL model for a whole structure. Furthermore, these numerical models were supported by experiments in a lab. All measured data was compared with simulation results and they were confirmed in good agreement in general. In addition to this, the relation between mode shapes and control by piezoelectric patches occupying a broader area than an ideal actuator was studied to find the conditions for more stable control of flat and curved plates. In conclusion, as discussed for active control with beams, AC/PSOLD treatment, which consists of a piezoelectric actuator directly attached to a base structure and a stand-off layer with a viscoelastic core and elastic constraining patch laminated on the piezoelectric actuator, was clarified to give the most efficient and robust active control results for plates regardless of the curvature of all HAPCLD treatments dealt within this thesis as well. AC/PSOLD treatment could give similar reductions with smaller control gain in simulation. And, larger reductions were obtained with measured transfer functions in experiments than other configurations.
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Chong, Ian Ian. "Vibration control and genetic algorithm based design optimization on self-sensing active constrained layer damped rotating plates." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2493698.
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Geng, Twzen-Shang. "Enhancement of the Dynamic Buckling Load and Analysis of Active Constrained Layer Damping with Extension and Shear Mode Piezoceramic Actuators." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27917.
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We consider geometric and material nonlinearities when studying numerically, by
the finite element method, transient three-dimensional electroelastic
deformations of a graphite-epoxy square plate sandwiched between two
piezoceramic (PZT) layers. Points on the four edges of the bottom surface
of the plate are restrained from moving vertically. The two opposite edges
of the plate are loaded
by equal in-plane compressive loads that increase linearly
with time and the other two edges are kept traction free. The plate material
is modeled as orthotropic and neoHookean. For the transversely isotropic
PZT the second Piola-Kirchhoff stress tensor and the electric displacement
are expressed as second degree polynomials in the Green-St. Venant strain
tensor and the electric field. Both direct and converse piezoelectric
effects are accounted for in the PZT. The plate is taken to have buckled
when its centroidal deflection equals three times the plate thickness.
The dynamic buckling load for the plate is found to strongly depend upon the
rate of rise of the applied tractions. With the maximum electric field
limited to
1kV/mm, the buckling load is enhanced by 18.3$\%$ when the PZT elements are
activated. For a peak electric field of 30kV/mm, the buckling load
increased by 58.5$\%$. When more than 60$\%$ of the surface area of the top
and the bottom surfaces of the plate are covered by the PZT layers, then
square PZT elements placed symmetrically about the plate centroid provide
a larger enhancement in the buckling load than rectangular shaped or
cross-shaped PZT elements. An increase in the plate thickness relative
to that of the PZT actuators decreases the effectiveness of
the PZT in enhancing the buckling load for the plate.
The finite element code was modified to also analyze, in time domain, transient
deformations of a viscoelastic material for which the second Piola-Kirchhoff
stress tensor is expressed as a linear functional of the strain history of
the Green-St. Venant strain tensor. It was used to analyze
three-dimensional deformations of a thick laminated plate with layers
made of aluminum, a viscoelastic material and a PZT. The following two
arrangements of layers are considered. In one case a central PZT layer
is surrounded on both sides by viscoelastic layers and aluminum layers
are on the outside surfaces. The PZT is poled in the longitudinal
direction and an electric field is applied in the thickness direction.
Thus shearing deformations of the PZT layer are dominant. In the second
arrangement, the aluminum layer is in the middle and the PZT layers are
on the outside. The poling direction and the electric field are in the
thickness direction; thus its extensional deformations are predominant.
Three indices are used to gauge the damping of motion of plate particles,
and the effectiveness of PZT actuators in enhancing this damping. It is
found that the optimum thickness of the viscoelastic layers for maximum
total energy dissipation is the same for each set-up.
Also, the total thickness of the PZT layers which results in the maximum
value of one of these indices of energy dissipation is the same for the
two set-ups. Both arrangements give the largest value of this index
for a plate of aspect ratio 10.
Buckling behavior of a sandwich plate containing a soft core is
also studied. The effects of the ratio of the elastic moduli
of the outer layers to those of the core, and of the core
thickness on the buckling load are analyzed.
The top and the bottom layers are connected by very stiff blocks on
two opposite edges where in-plane compressive time-dependent tractions
are applied.<br>Ph. D.
6
Huang, Yao-Hsin. "Some fundamental issues of constrained layer damping treatments /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/7046.
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Al-Ajmi, Mohammed. "Homogenization and topology optimization of constrained layer damping treatments." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1537.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2004<br>Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Schultze, John Francis. "Evaluation of analytical and experimental methods to predict constrained layer damping behavior." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09122009-040317/.
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Sandin, Joakim. "Analysis Methods for Structures with Visco-Elastic Damping Treatment." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13250.
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During aircraft development, the impact of vibrations is examined and how this affects the aircraft structure under different conditions. Those vibrations can damage electronic equipment that are installed within the fuselage and can even lead to material fatigue within the structure. To reduce vibrations there are two approaches that are preferred to use, installing vibration insulators attached between the structure and the electrical component or change the design of the structure to a stiffer one. Those methods are easiest to implement in an early stage of the development but in later stages, when vibration problems usually are detected, it is too difficult and expensive to do major changes of the structure and there is lack of space to implement vibration insulators. A third method is then to apply passive damping in form of damper mats to surfaces on structures where critical vibrations occurs. The effects on the structural behavior when damper mats are applied to a certain structure are studied in this thesis work. The purpose is to get deeper knowledge about how damper mats can be used to reduce vibrations in aircraft structures. The type of damper mat that is studied is known as Constrained Layer Damping, CLD, which is a sandwich of a visco-elastic material layer and a stiffer constraining material layer. Modelling and simulation methods that are based on commercial FE-software have been developed. The analysis method is based on doing a modal analysis with structural damping taken into account. This makes it possible to predict the overall global damping at each structural mode. The models for damper mats have in this project been verified with experimental testing using typical damper mats. The methodology can be used to predict the behavior of damped structures in order to obtain an effective and lightweight passive damping solution.<br>Under utvecklingen av flygplan undersöks hur vibrationer påverkar flygplansstrukturen under olika förutsättningar. Dessa vibrationer kan skada elektronisk utrustning som är monterad i flygplanskroppen och kan även göra så att materialutmattning uppstår i flygplansstrukturen. För att motverka vibrationer finns det två metoder som är att föredra, antingen att montera vibrationsisolatorer mellan de elektroniska utrustningarna och strukturen eller att ändra designen på strukturer till en styvare. Dessa metoder är enkla att implementera i ett tidigt steg i utvecklingsprocessen men i senare steg, då vibrationsproblem ofta upptäcks, så är det för komplicerat och för dyrt att göra större ändringar på strukturen och så är det ont om plats för att kunna installera vibrations isolatorer. En tredje metod är istället att implementera passiv dämpning i form av dämpningsmattor på ytor av strukturen där kritiska vibrationer uppstår. Effekterna av det strukturella uppförandet när dämpningsmattor är applicerade på en viss struktur har studerats i det här examensarbetet. Syftet är att få en fördjupad kunskap om hur dämpningsmattor kan användas för att reducera vibrationer i flygplan strukturer. Den typ av dämpningsmatta som har studerats är känd som Constrained Layer Damping, CLD, vilken är en sandwich av ett visko-elastiskt lager samt ett styvare lager. Modellerings och simuleringsmetoder som är baserade på kommersiella FE-mjukvaror har utvecklats. Analysmetoderna är baserade på att utföra modalanalys tillsammans med strukturell dämpning. Detta möjliggör att förutse den övergripande dämpningen vid varje strukturell mod. Modellerna för dämpningsmattorna har i det här projektet verifierats med experimental testning av typiska dämpningsmattor. Metodiken kan användas till att prediktera beteendet av dämpade strukturer för att uppnå en effektiv och lättviktig passiv dämpningslösning.
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Bateman, Michael John. "Constrained viscoelastic layer damping of thick aluminum plates: design, analysis, and testing." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30674.
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Approved for public release, distribution is unlimited<br>Modern naval warfare has been increasingly dependent upon the acoustic silencing of the participants. Constrained viscoelastic layer damping of vibrating elements is one method which can be used to meet acoustic silencing goals. This paper considers constrained viscoelastic layer damping treatments applied to a thick aluminum plate, including single layer, double layer, a milled pocket plate, and a milled 'floating element' configuration. High modal damping values were obtained for each configuration. The Modal Strain Energy method, using finite element analysis to estimate modal loss factors, was investigated for use as a tool in constrained viscoelastic layer damping design. A comparison of experimentally measured frequency response and modal loss factors with those predicted by the modal strain energy method is presented to confirm the possible use of the modal strain energy method as a design tool.
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Jeung, Yeun S. "Finite element analysis for sandwich structures with a viscoelastic-constrained layer /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9999.
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Gallimore, Craig Allen. "Passive Viscoelastic Constrained Layer Damping Application for a Small Aircraft Landing Gear System." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35350.
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The main purpose of this report was to test several common viscoelastic polymers and identify key attributes of their applicability to a small aircraft landing gear system for improved damping performance. The applied viscoelastic damping treatment to the gear was of a constrained layer type, promoting increased shear deformation over free surface treatments, and therefore enhanced energy dissipation within the viscoelastic layer. A total of eight materials were tested and analyzed using cyclic loading equipment to establish approximate storage modulus and loss factor data at varying loading frequencies. The three viscoelastic polymers having the highest loss factor to shear modulus ratio were chosen and tested using a cantilever beam system. A Ross, Kerwin, and Ungar analysis was used to predict the loss factor of the cantilever beam system with applied treatment and the predictions were compared to experimental data.
Customer requirements often govern the scope and intensity of design in many engineering applications. Limitations and constraints, such as cost, weight, serviceability, landing gear geometry, environmental factors, and manufacturability in regards to the addition of a viscoelastic damping treatment to a landing gear system are discussed.
Based on results found from theoretical and experimental testing, application of a damping treatment to a small aircraft landing gear system is very promising. Relatively high loss factors were seen in a cantilever beam for simple single layer constrained treatments for very low strain amplitudes relative to strains seen during loading of the landing gear. With future design iterations, damping levels several times those seen in this document will be seen with a constrained treatment applied to a landing gear system.<br>Master of Science
13
Kung, Shih-Wei. "Vibration analysis of beams and rectangular plates with multiple constrained layer damping patches /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487949150071853.
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Verstappen, André Paul. "Passive damping treatments for controlling vibration in isotropic and orthotropic structural materials." Thesis, University of Canterbury. Mechanical Engineering, 2015. http://hdl.handle.net/10092/10197.
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The structural vibration damping behaviour of plates and beams can be improved by the application of viscoelastic passive damping materials. Unconstrained layer damping treatments applied to metal plate systems were studied experimentally. Design and modelling of novel fibre reinforced constrained layer damping materials was performed, and implementation of these composite damping materials into laminated composite sandwich constructions commonly used as structural elements within large composite marine vessels was explored. These studies established effective methods for examining, designing and applying damping materials to metal and composite marine structures.
Two test fixtures were designed and constructed to facilitate testing of viscoelastic material damping properties to ISO 6721-3 and ASTM E756. Values of material damping made in accordance with ASTM E756 over a range of temperatures were compared to values produced by a Dynamic Mechanical Analyser (DMA). Glass transition temperatures and peak damping values were found to agree well, although results deviated significantly at temperatures above the glass transition temperature.
The relative influence of damping layer thickness, ambient temperature, edge conditions, plate dimensions and substrate material on the system damping performance of metal plates treated with an unconstrained viscoelastic layer was investigated experimentally. This investigation found that substrate material had the greatest influence on system damping performance, followed by damping layer thickness and plate size. Plate edge conditions were found to have little influence on the measured system damping performance. These results were dependent on the values of each variable used in the study.
Modal damping behaviour of a novel fibre reinforced composite constrained layer damping material was investigated using finite element analysis and experimental methods. The material consisted of two carbon fibre reinforced polymer (CFRP) layers surrounding a viscoelastic core. Opposing complex sinusoidal fibre patterns in the CFRP face sheets were used to achieve stress-coupling by way of orthotropic anisotopy about the core. A finite element model was developed in MATLAB to determine the modal damping, displacement, stress, and strain behaviour of these complex patterned fibre constrained layer damping (CPF-CLD) materials. This model was validated using experimental results produced by modal damping measurements on CPF-CLD beam test specimens. Studies of multiple fibre pattern arrangements found that fibre pattern properties and the resulting localised material property distributions influenced modal damping performance.
Inclusion of CPF-CLD materials in laminated composite sandwich geometries commonly used in marine hull and bulkhead constructions was studied experimentally. Composite sandwich beam test specimens were fabricated using materials and techniques frequently used in industry. It was found that the greatest increases in modal damping performance were achieved when the CPF-CLD materials were applied to bulkhead geometries, and were inserted within the sandwich structure, rather than being attached to the surface.
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Velazquez, Carlos A. "Electromechanical surface damping combining constrained layer and shunted piezoelectric materials with passive electrical networks of second order /." Online version of thesis, 1995. http://hdl.handle.net/1850/12217.
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Ahmad, Naveed. "Passive Damping in Stiffened Structures Using Viscoelastic Polymers." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79566.
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Noise and vibration suppression is an important aspect in the design process of structures and machines. Undesirable vibrations can cause fatigue in a structure and are, therefore, a risk to the safety of a structure. One of the most effective and widely used methods of mitigating these unwanted vibrations from a system is passive damping, by using a viscoelastic material. This dissertation will primarily focus on constrained layer passive damping treatments in structures and the investigation of associated complex modes. The key idea behind constrained damping treatment is to increase damping as affected by the presence of a highly damped core layer vibrating mainly in shear. Our main goal was to incorporate viscoelastic material in a thick stiffened panel with plate-strip stiffeners, to enhance the damping characteristics of the structure.
First, we investigated complex damped modes in beams in the presence of a viscoelastic layer sandwiched between two elastic layers. The problem was solved using two approaches, (1) Rayleigh beam theory and analyzed using the principle of virtual work, and (2) by using 2D plane stress elasticity based finite-element method. The damping in the viscoelastic material was modeled using the complex modulus approach. We used FEM without any kinematic assumptions for the transverse shear in both the core and elastic layers. Moreover, numerical examples were studied, by including complex modulus in the base and constraining layers. The loss factor was calculated by modal strain energy method, and by solving a complex eigenvalue problem. The efficiency of the modal strain energy method was tested for different loss factors in the core layer. Complex mode shapes of the beam were also examined in the study, and a comparison was made between viscoelastically damped and non-proportionally damped structures.
Secondly, we studied the free vibration response of an integrally stiffened and/or stepped plate. The stiffeners used here were plate-strip stiffeners, unlike the rib stiffeners often investigated by researchers. Both plate and stiffeners were analyzed using the first-order shear deformation theory. The deflections and rotations were assumed as a product of Timoshenko beam functions, chosen appropriately according to the given boundary conditions. Unlike Navier and Levy solution techniques, the approach used here can also be applied to fully clamped, free and cantilever supported stiffened plates. The governing differential equations were solved using the Rayleigh-Ritz method. The development of the stiffness and the mass matrices in the Ritz analysis was found to consume a huge amount of CPU time due to the recursive integration of Timoshenko beam functions. An approach is suggested to greatly decrease this amount of CPU time, by replacing the recursive integration in a loop structure in the computer program, with the analytical integration of the integrand in the loop. The numerical results were compared with the exact solutions available in the literature and the commercially available finite-element software ABAQUS. Some parametric studies were carried out to show the influence of certain important parameters on the overall natural frequencies of the stiffened plate.
Finally, we investigated the damped response of an adhesively bonded plate employing plate-strip stiffeners, using FSDT for both the plate and stiffeners. The problem was analyzed using the principle of virtual work. At first, we did not consider damping in the adhesive in order to validate our code, by comparing our results with those available in the literature as well as with the results obtained using ABAQUS 3D model. The results were found to be highly satisfactory. We also considered the effect of changing the stiffness of the adhesive layer on the vibration of the bonded system. As a second step, we included damping in the stiffened structure using complex modulus approach, a widely used technique to represent the rheology of the viscoelastic material. We observed an overall increase in the natural frequencies of the system, due to the damping provided by the viscoelastic material. Moreover, it was noticed that when the thickness of the adhesive layer is increased, the natural frequencies and loss factor of the stiffened structure decrease. A viscoelastic material with high loss factor and small thickness will be a perfect design variable to obtain overall high damping in the structure.<br>Ph. D.
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Rose, Michael Thomas. "Noise Control of Vacuum-Assisted Toilets." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8789.
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Vacuum-assisted toilets make use of a large pressure difference between the ambient pressure and a vacuum tank to transport waste from the toilet bowl to the septic tank. This process requires 98% less water per flush making it an attractive product for transport vehicles such as airplanes, cruise ships, and trains. Unfortunately, the water savings come at the cost of high noise levels. This thesis investigates the acoustic characteristics of a vacuum-assisted toilet flush and several methods to reduce the radiated noise. Some methods include changing rinse parameters such as rinse pressure, rinse length, and rinse timing, adding structural damping of the bowl to reduce re-radiation, inserting a tube between the bowl and valve that utilizes a larger bend radius and longer tube length than what is currently installed, and modifying the valve. The most effective solution without requiring more water per flush was to insert a tube. The initial peak level was reduced by 16 dB and the steady-vacuum noise was reduced by 5 dB. Evidence of evanescent decay and reduced flow velocity as possible mechanisms for the noise reduction are presented and discussed. Rinse variations show a strong impact of the rinse-tube interaction on the noise reduction. In addition to these techniques, a modified flush plate opening and closing velocity profile is suggested which optimizes the sound generated by the opening and closing of the valve. Finally, a promising dual-valve solution that may take extra coordination of vacuum-assisted toilet manufacturers and airplane/cruise ship/train manufacturers is presented. By placing a secondary valve near the septic tank, the main noise from the valve is significantly reduced.
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Castel, Alexis. "Comportement vibratoire de structures composites intégrant des éléments amortissants." Phd thesis, Université de Bourgogne, 2013. http://tel.archives-ouvertes.fr/tel-00983378.
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Ce travail traite de la modélisation de structures composites intégrant des éléments amortissants passifs. Un modèle de plaque "équivalent simple couche" générique utilisant des fonctions de description du cisaillement transverse est présenté. Plusieurs méthodes d'obtention de ces fonctions sont décrites, permettant de retrouver des modèles classiques ou issus de la littérature. Deux nouvelles méthodes d'obtention de ces fonctions sont aussi présentées.Plusieurs méthodes de discrétisation adaptées au modèle générique sont étudiées. La méthode de Navier permet de tester la qualité de chaque modèle associé à un jeu de fonctions de description du cisaillement transverse. La méthode de Rayleigh-Ritz permet l'étude du comportement vibratoire d'une plaque rectangulaire munie d'un ou plusieurs patchs viscocontraints. Plusieurs éléments finis issus de la littérature, adaptés au modèle, sont aussi présentés.À l'aide de la méthode de Navier, une étude numérique du comportement statique et dynamique de plusieurs configurations de plaques permet la comparaison des différents modèles présentés. La méthode de Rayleigh-Ritz est utilisée pour étudier le comportement vibratoire d'une plaque munie d'un patch viscocontraint. Une comparaison des résultats obtenus avec le modèle présenté et ceux issus de calculs éléments finis tridimensionnels permet de valider notre modèle. Une étude énergétique de la plaque patchée permet d'illustrer le comportement du patch. Enfin une méthode inverse d'identification des matériaux viscoélastiques, basées sur une combinaison du modèle décrit et d'un algorithme génétique, montre une application du modèle.
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Kumar, Navin. "Vibration control of panels using hybrid active constrained layer damping." Thesis, 2007. http://localhost:8080/iit/handle/2074/5188.
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"Modeling and implementation of plates with enhanced active constrained layer damping." 2004. http://library.cuhk.edu.hk/record=b5892084.
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by Dai Ruoli.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.<br>Includes bibliographical references (leaves 85-88).<br>Abstracts in English and Chinese.<br>ABSTRACT --- p.i<br>摘要 --- p.ii<br>ACKNOWLEDGEMENTS --- p.iii<br>TABLE OF CONTENTS --- p.iv<br>LIST OF FIGURES --- p.vi<br>LIST OF TABLES --- p.ix<br>Chapter CHAPTER ONE - --- BACKGROUND AND LITERATURE REVIEW --- p.1<br>Chapter 1.1 --- Piezoelectric Materials --- p.2<br>Chapter 1.2 --- Literature Review on Vibration Control --- p.6<br>Chapter 1.2.1 --- Passive control (PCL treatment) --- p.6<br>Chapter 1.2.2 --- Active control (PA treatment) --- p.7<br>Chapter 1.2.3 --- Active passive hybrid control (ACL and EACL treatment) --- p.8<br>Chapter 1.3 --- Finite Element Method --- p.11<br>Chapter 1.4 --- Positive Position Feedback Control --- p.12<br>Chapter 1.5 --- Damping --- p.13<br>Chapter 1.5.1 --- GHM method --- p.13<br>Chapter 1.5.2 --- Rayleigh damping --- p.13<br>Chapter 1.6 --- Thesis Objectives and Outline --- p.15<br>Chapter CHAPTER TWO - --- SYSTEM MODELING --- p.16<br>Chapter 2.1 --- Assumptions --- p.17<br>Chapter 2.2 --- Elements --- p.18<br>Chapter 2.3 --- FEM Matrices --- p.22<br>Chapter 2.3.1 --- Element matrices component related to in-plane displacement --- p.22<br>Chapter 2.3.2 --- Element matrices component related to bending displacement --- p.30<br>Chapter 2.3.3 --- Element matrices component related to shear strain --- p.35<br>Chapter 2.3.4 --- Overall element matrices --- p.38<br>Chapter 2.3.5 --- Piezoelectric control forces --- p.39<br>Chapter 2.4 --- Damping --- p.40<br>Chapter 2.4.1 --- Damping due to the viscoelastic materials --- p.40<br>Chapter 2.4.2 --- Inherent structural damping --- p.43<br>Chapter 2.5 --- Edge Elements --- p.44<br>Chapter 2.6 --- Model Reduction --- p.46<br>Chapter CHAPTER THREE - M --- ODEL VALIDATION --- p.47<br>Chapter 3.1 --- Beam with Passive ACL Damping Treatment --- p.48<br>Chapter 3.2 --- Clamped-Clamped Plate with Fully Covered ACL --- p.50<br>Chapter 3.3 --- Cantilever Plate with ACL/EACL Patch --- p.52<br>Chapter CHAPTER FOUR - --- STUDIES ON EACL PATCH LOCATION --- p.57<br>Chapter 4.1 --- Overview of the Numerical Examples --- p.58<br>Chapter 4.2 --- Patch Location on Passive Damping Ability --- p.61<br>Chapter 4.3 --- Patch Location on Actuating Ability --- p.65<br>Chapter 4.4 --- Discussion on Patch Location --- p.69<br>Chapter CHAPTER FIVE - --- SYSTEM IMPLEMENTATION --- p.71<br>Chapter 5.1 --- Experimental Setup --- p.71<br>Chapter 5.1.1 --- Open loop test --- p.72<br>Chapter 5.1.2 --- Closed loop test --- p.72<br>Chapter 5.2 --- Controller Design --- p.74<br>Chapter 5.3 --- Results and Discussion --- p.76<br>Chapter CHAPTER SIX - --- CONCLUSION AND FUTURE WORK --- p.81<br>Chapter 6.1 --- Summary and Conclusion --- p.81<br>Chapter 6.2 --- Recommendations for Future Research --- p.82<br>"APPENDIX - PZT data sheet from PIEZO SYSTEMS, INC" --- p.83<br>BIBLIOGRAPHY --- p.85
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Chen, Lin-Hung, and 陳林宏. "Studies on Active and Passive Constrained Layer Damping for the Vibration Reduction of Cylindrical Shells." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/01040505749418225219.
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博士<br>國立臺灣科技大學<br>機械工程系<br>87<br>This investigation presents vibration response of cylindrical shells with passive and active constrained layer damping (CLD) treatments. The research topics include cylindrical shell with passive constrained layer damping (PCLD), active constrained layer damping (ACLD) and active control (AC). A thin shell theory in conjunction with the Donnell-Mushtari-Vlasov assumptions is employed to yield models for all cases. The assumed-mode method follows to discretize the energy expressions and subsequently yields the equations of motion. As to ACLD, it is formed from PCLD by replacing with the constraining layer, a piezoceramic-based (PZT) self-sensing actuator. The proportional plus the derivative (PD) and the positive position feedback (PPF) control laws are discussed in ACLD and AC cases. To yield the equations of motion of AC case, one simply lets the viscoelastic material (VEM) vanish from the ACLD case.
The numerical results emphasize not only the effects of treatment length, of constraining layer (CL) thickness and stiffness, and of VEM thickness for PCLD, but also the comparison of PD and PPF controls, for ACLD and AC. The effect of VEM layer to control force reduction is discussed as well. The results of this research, to the knowledge of the author, are original and provide the engineers useful information about damping effects due to various parameters for PCLD, ACLD and AC treatments and the comparison in between.
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Dewangan, Palash. "Passive Viscoelastic Constrained Layer Damping for Structural Application." Thesis, 2009. http://ethesis.nitrkl.ac.in/1374/1/MTECH_THESIS_PALASH_DEWANGAN(207ME109).pdf.
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The purpose behind this study is to predict damping effects using method of passive viscoelastic constrained layer damping. Ross, Kerwin and Unger (RKU) model for passive viscoelastic damping has been used to predict damping effects in constrained layer sandwich cantilever beam. This method of passive damping treatment is widely used for structural application in many industries like automobile, aerospace, etc.
The RKU method has been applied to a cantilever beam because beam is a major part of a structure and this prediction may further leads to utilize for different kinds of structural application according to design requirements in many industries. In this method of damping a simple cantilever beam is treated by making sandwich structure to make the beam damp, and this is usually done by using viscoelastic material as a core to ensure the damping effect. Since few years in past viscoelastic materials has been significantly recognized as the best damping material for damping application which are usually polymers. Here some viscoelastic materials have been used as a core for sandwich beam to ensure damping effect.
Due to inherent complex properties of viscoelastic materials, its modeling has been the matter of talk. So in this report modeling of viscoelastic materials has been shown and damping treatment has been carried out using RKU model. The experimental results have been shown how the amplitude decreases with time for damped system compared to undamped system and further its prediction has been extended to finite element analysis with various damping material to show comparison of harmonic responses between damped and undamped systems.
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Pai, Rohan Vinay. "Parameter study on topology optimization of constrained layer damping treatments." 2003. http://etd.utk.edu/2003/PaiRohan.pdf.
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Thesis (M.S.)--University of Tennessee, Knoxville, 2003.<br>Title from title page screen (viewed Mar. 29, 2004). Thesis advisor: Arnold Lumsdaine. Document formatted into pages (x, 87 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 79-86).
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Wang, Horng-Jou, and 王宏洲. "Vibration and Dynamic Stability of Circular Plates with Constrained Damping Layer." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/88407711161039084421.
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博士<br>國立成功大學<br>機械工程學系碩博士班<br>91<br>Vibration, damping and dynamic stability of sandwich circular plates with constrained damping layer are investigated. The governing equations of sandwich circular plate system are derived by a discrete layer annular finite element method. The transverse shear effects are included in the finite element, and it is convenient to handle the thick or thin plate problem. The material properties of isotropic, linear and incompressible viscoelastic materials in damping layer are described by complex representations. The free vibration and dynamic stability of stationary and rotational sandwich circular plates are the focus of this thesis. In the mathematical modeling, initial stress distribution induced by rotational and external load effects are obtained from the solutions of static problems and are taken into account in the strain energy expression to calculate the geometry stiffness matrices. The governing equations with complex coefficients are derived, and natural frequencies, modal loss factors and boundaries between dynamic stability region and instability region can be solved.
The effects of many design parameters, such as stiffness and thickness of the damping and constraining layers, treatment sizes and rotational speeds, are discussed. Numerical results are shown that the thicker damping layer or the larger treatment size is not always provided better damping properties of plate systems. The modal loss factors of systems are decreased with increasing of rotational speeds. Moreover, the effects of the constrained damping layer tend to stabilize circular plate systems.
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Yang, Wen-Pei, and 楊文佩. "Vibration Analysis of a Traveling Beam with a Constrained Layer Damping." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/fr4y27.
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碩士<br>國立成功大學<br>機械工程學系碩博士班<br>90<br>The objective of this dissertation is to study the vibration and damping of a traveling beam with a constrained layer damping. The discrete layer finite element method and the Hamilton’s principle are employed to derive the finite-element equations of motion for the traveling beam including transverse shear effects.
The middle layer is the linear viscoelastic material layer, assuming that viscoelastic material is almost incompressible. The extensional and shear moduli of the viscoelastic material are described by complex quantities. Complex-eigenvalued problem are solved by state-space method, and the frequencies and modal loss factor of the composite beam are extracted. The effects of stiffness and thickness of the viscoelastic and constrained layers on natural frequencies and modal loss factors of traveling beam are presented. It is shown that the viscoelastic material can reduce the natural frequencies and the critical speed of the traveling beam is decreased. Tension fluctuations are the dominant source of excitation in traveling
materials. The regions of dynamic instability are determined by Bolotin’s method and numerical results are shown that the constrained damping layer attached to beam tends to stabilize the traveling material. The effects of various parameters, such as types of viscoelastic material response and thickness, on dynamic stability are also investigated.
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于善淳. "Vibration Reduction of an Annular Rotating Plate with Constrained Layer Damping Treatment." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/98169505048096616052.
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博士<br>國立臺灣科技大學<br>機械工程系<br>90<br>In this dissertation, vibration suppression of a three-layer circular plate with a viscoelastic core is studied. First of all, based on Love''s thin shell theory and by referring to the theory of Mead and Markus, the equations of motion for a three-layer rotating shell with a constrained layer damping (CLD) are derived via energy principles. The derived equations can be applied to structures of various geometries commonly encountered in engineering applications, for example, cylindrical shells, circular rings, circular plates, etc.. The response of the transverse displacement subjected to transverse loading is the focus of this study. By adopting Donnell-Mushtari-Vlasov''s assumption, the equations are simplified to contain only three displacement variables of the main structure. One is the transverse displacement and the other two are the in-plane displacements. Since the applications of the circular plates in engineering are extensive, this has a comprehensive study on the contribution of the CLD on the vibration suppression of the circular plate, which includes both static and rotating systems. At last, the response equation of the plate can be simplified to be expressed in terms of the transverse displacement and contains n linear single degree of freedom systems with hysteretic damping. The discussion begins with the contribution of viscoelastic core on the vibration suppression of a circular plate. Then, the damping effects caused by the CLD and the viscous damper on a spring-mass-damping (SMD) and plate system are compared. At last, the CLD applied to a rotating system is investigated. The results provide comprehensive explanation on vibration suppression of a circular plate with passive constrained layer damping (PCLD) and can be used as references for engineering designs.
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Zheng, H., G. S. H. Pau, and Guirong Liu. "Optimization of Passive Constrained Layer Damping Treatments for Vibration Control of Cylindrical Shells." 2003. http://hdl.handle.net/1721.1/3705.
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This paper presents the layout optimization of passive constrained layer damping (PCLD) treatment for vibration control of cylindrical shells under a broadband force excitation. The equations governing the vibration responses are derived using the energy approach and assumed-mode method. These equations provided relationship between the integrated displacement response over the whole structural volume, i.e. the structural volume displacement (SVD), of a cylindrical shell to structural parameters of base structure and multiple PCLD patches, Genetic algorithms (GAs) based penalty function method is employed to find the optimal layout of rectangular PCLD patches with minimize the maximum displacement response of PCLD-treated cylindrical shells. Optimization solutions of PCLD patches’ locations and shape are obtained under the constraint of total amount of PCLD in terms of percentage added weight to the base structure. Examination of the optimal layouts reveals that the patches tend to increase their coverage in the axial direction and distribute over the whole surface of the cylindrical shell for optimal control of the structural volume displacement.<br>Singapore-MIT Alliance (SMA)
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Pau, G. S. H., H. Zheng, and Guirong Liu. "A Comparative Study on Optimization of Constrained Layer Damping for Vibration Control of Beams." 2003. http://hdl.handle.net/1721.1/3697.
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This paper presents a comparison of optimization algorithms for constrained damping (CLD) patches’ layout to minimize the maximum vibration response of the odd modes, which constitutes the dominant acoustic radiation, of a simply-supported beam excited by a harmonic transverse force. An analytical model based on Euler-Bernoulli beam assumptions is derived first to relate the displacement response of the beam with bonded CLD patches and their layout. Four different nonlinear optimization methods/algorithms are then respectively used to optimize the CLD patches’ locations and lengths with aim of minimum displacement amplitude at middle of the beam. The considered methods include subproblem approximation method, the first-order method, sequential quadratic programming (SQP) and genetic algorithm (GA). The efficiency of each considered optimization method is evaluated and also compared in terms of obtained optimal beam displacement. The results show that GA is most efficient in obtaining the best optimum for this optimization problem in spite of highest computation efforts required to improve its stability.<br>Singapore-MIT Alliance (SMA)
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Lin, Chung-Yi, and 林忠義. "Vibration and Stability of Rotating Pre-twisted Beam Systems with a Constrained Damping Layer." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/56785086549083057031.
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博士<br>國立成功大學<br>機械工程學系碩博士班<br>91<br>The objective of this dissertation is to study the vibration and stability problems of rotating pre-twisted beam systems with passive or smart constrained damping layer subjected, respectively, to axial and follower forces by using the finite element method. The complex modulus is used for the viscoelastic material. In the dynamic stability problems, the regions of instability are determined by using Bolotin’s procedure, modified for the complex case.
In the passive constrained layer damping (PCLD) treatments, two models, the rotating pre-twisted sandwich blade and the spinning pre-twisted sandwich beam, are studied. The equations of motion of rotating pre-twisted sandwich blades or spinning pre-twisted beams subjected, respectively, to axial and follower forces are derived by Hamilton’s principle. The vibration and stability behavior of the rotating system with PCLD treatment are discussed and compared with no damping treatment. The results reveal that rotating systems with the PCLD treatment subjected to longitudinal forces are more stable than that without damping treatment. The dynamic instability problem of rotating systems subjected to follower forces is also studied. For the rotating system with a PCLD treatment, as the flutter instability occurs, the first and second natural frequencies are not equal. The amplitude at the resonance is reduced as rotating beam systems with a PCLD treatment. The effect of pre-twisted angle on the system damping is detrimental for rotating pre-twisted sandwich blade systems, but it is beneficial for spinning pre-twisted sandwich beam systems.
In the smart constrained layer damping (SCLD) treatments, the vibration and stability behavior of rotating pre-twisted blade systems with a smart constrained layer damping (SCLD) treatment are studied. The SCLD design consists of viscoelastic shear layer sandwiched between a piezoelectric sensor and a piezoelectric actuator. This composite SCLD when bounded to a vibrating structure acts as a smart treatment. The piezoelectric sensor layer measures the vibration response of the structure and a feedback controller is provided that regulates the axial deformation of the piezoelectric actuator, thereby provide adjustable and significant damping in the structure. The proportional and derivative controller (PD controller) is used to study the effect of the SCLD on the vibration suppression performance and stability behavior. The PCLD systems could be obtained as the controller is closed. The results show that SCLD systems have better stability and vibration suppression performance by regulating the proportional and derivative gains.
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Nault, James Robert. "Analytical and experimental investigation of constrained viscoelastic layer damping for a plate and shell model." Thesis, 1988. http://hdl.handle.net/10945/22906.
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Ansari, Masoud. "Optimal Vibration Control in Structures using Level set Technique." Thesis, 2013. http://hdl.handle.net/10012/7948.
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Vibration control is inevitable in many fields, including mechanical and civil engineering. This matter becomes more crucial for lightweight systems, like those made of magnesium. One of the most commonly practiced methods in vibration control is to apply constrained layer damping (CLD) patches to the surface of a structure. In order to consider the weight efficiency of the structure, the best shape and locations of the patches should be determined to achieve the optimum vibration suppression with the lowest amount of damping patch. In most research work done so far, the shape of patches are assumed to be known and only their optimum locations are found. However, the shape of the patches plays an important role in vibration suppression that should be included in the overall optimization procedure.
In this research, a novel topology optimization approach is proposed. This approach is capable of finding the optimum shape and locations of the patches simultaneously for a given surface area. In other words, the damping optimization will be formulated in the context of the level set technique, which is a numerical method used to track shapes and locations concurrently.
Although level set technique offers several key benefits, its application especially in time-varying problems is somewhat cumbersome. To overcome this issue, a unique programming technique is suggested that utilizes MATLAB© and COMSOL© simultaneously.
Different 2D structures will be considered and CLD patches will be optimally located on them to achieve the highest modal loss factor. Optimization will be performed while having different amount of damping patches to check the effectiveness of the technique. In all cases, certain constraints are imposed in order to make sure that the amount of damping material remains constant and equal to the starting value. Furthermore, different natural frequencies will be targeted in the damping optimization, and their effects will also be explained.
The level set optimization technique will then be expanded to 3D structures, and a novel approach will be presented for defining an efficient 4D level set function to initialize the optimization process. Vibrations of a satellite dish will be optimally suppressed using CLD patches. Dependency of the optimum shape and location of patches to different parameters of the models such as natural frequencies and initial starting point will be examined. In another practical example, excessive vibrations of an automotive dash panel will be minimized by adding damping materials and their optimal distribution will be found.
Finally, the accuracy of the proposed method will be experimentally confirmed through lab tests on a rectangular plate with nonsymmetrical boundary conditions. Different damping configurations, including the optimum one, will be tested. It will be shown that the optimum damping configuration found via level set technique possesses the highest loss factor and reveals the best vibration attenuation.
The proposed level set topology optimization method shows high capability of determining the optimum damping set in structures. The effective coding method presented in this research will make it possible to easily extend this method to other physical problems such as image processing, heat transfer, magnetic fields, etc. Being interconnected, the physical part will be modeled in a finite element package like COMSOL and the optimization advances by means of Hamilton-Jacobi partial differential equation. Thus, the application of the proposed method is not confined to damping optimization and can be expanded to many engineering problems.
In summary, this research:
- offers general solution to 2D and 3D CLD applications and simultaneously finds the best shape and location of the patches for a given surface area (damping material);
- extends the level set technique to concurrent shape and location optimization;
- proposes a new numerical implementation to handle level set optimization problems in any complicated structure;
- makes it possible to perform level set optimization in time dependent problems;
- extends level set approach to higher order problems.