bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Models for the Piezoelectric Actuation in Ultrasonic Traveling Wave Motors
Authors: Krome J. W. , Wallaschek J.
Published: August 2009

By appropriate superposition of two standing waves, a traveling wave can be excited in the ring-shaped stator of a traveling wave motor. Thus, the material points on the surface of the stator perform an elliptical motion. A second disk, pressed against the stator, is driven by frictional forces, generated in the interface between stator and rotor. Traveling wave motors produce a very high torque at low rotational speed. Their simple mechanical design and good controllability make these motors a very promising alternative to small electromagnetic motors. The mechanical oscillations of high frequency are excited by piezoelectric ceramic actuators, bonded to the surface of the stator. The dynamic behavior of the stator is strongly influenced by these actuators. Since it is difficult to produce big ceramic rings and bond them to the stators, single piezoelectric elements have to be used for the excitation of large stators. The geometry of the ceramic actuators as well as the stiffness of the bonding layer do have marked influence on the efficiency of the excitation, because the actuation mechanism is of induced strain type and the stator is excited by tangential stresses in the bonding layer. In this paper, the influence of the shape of the ceramics on the vibration of the stator is investigated using the finite element method. A detailed model taking into account the piezoelectric effect in the ceramic actuators as well as the exact geometry of the stator is used to calculate the transfer function between the electrical excitation and the mechanical vibrations of the stator. The results allow to compare the efficiency of different actuator configurations.
An Adaptive Fuzzy Control Algorithm for Model-Independent Active Vibration Damping of Flexible Beam-Like Structures
Authors: Cohen Kelly , Weller Tanchum , Levitas Joseph , Abramovich Haim
Published: August 2009

The present study deals with an AFCA (Adaptive Fuzzy Control Algorithm) for an Euler-Bemoulli approximation of a two-dimensional version of a cantilever beam-like orthogonal tetrahedral space truss. Transient disturbances, modeled as a unit impulse, excite all the modes of the beam. The resulting transverse displacement at the free end of the beam and its corresponding rate are observed by sensors placed there, and active control of the beam is provided by a collocated force actuator.

A design methodology, based on fuzzy logic which assumes no a priori knowledge of plant dynamics, for the closed-loop control algorithm results in relatively quick settling times, low overshoots and dying out of vibration within a few seconds. The control algorithm is enhanced and made much faster by eliminating the need of repeatedly solving the set of differential equations of motion of an emulated dynamic vibration absorber. When the control force is turned off after a mere 15 seconds, almost all the vibrational energy is dissipated as the beam returns to its undisturbed state throughout its length. In addition, the performance of the AFCA is insensitive to varying initial conditions. To examine the robustness of the control system to changes in the temporal dynamics of the cantilever beam, the transient disturbance response to a considerably perturbed plant is simulated. The Young's modulus of the beam was raised as well as lowered by 60%, substantially perturbing the natural frequencies of vibration compared to the nominal plant. The AFCA provided similar settling times and rates of vibrational energy dissipation, satisfying the aim of plant model independence.
Shape Control of an Adaptive Mirror at Different Angles of Inclination
Authors: Paradies Rolf , Hertwig Manfred , Elspass Wilfried J.
Published: August 2009

The topic of this paper is the quasi-static shape control of an adaptive mirror, which is deformed due to gravity at different angles of inclination. Next to the basic design aspects of the adaptive mirror, a comparison between the numerical and experimental results is presented. Special emphasis is given to the description of the experimental setup for the verification of the shape control. Since for this structure the gravity-induced deformations are in the order of micrometers, a speckle interferometric measurement system and phase-shifting techniques have been used. The experimental data obtained with respect to the out-of-plane displacement of the mirror confirm the results of the numerical simulations. Moreover, the efficiency of the shape control is investigated and a correction scheme is presented.
Analysis and Control of Microvibrations on ARTEMIS Satellite
Authors: Galeazzi Claudio , Morganti Francesco , Arduini Carlo , Gaudenzi Paolo
Published: August 2009

The need for a very high pointing accuracy and an extremely quiet on-board environment (micro-dynamic) has become an increasingly important issue in the most advanced space missions, such as the ARTEMIS telecommunication satellite. In the first part, this paper presents the activities carried out by Alenia Spazio (ALS) to analyze the effects of microvibrations on the satellite. In the second part, a feasibility study based on a smart structure is proposed to suppress the structural microvibrations. A numerical simulation of an intelligent structure based on piezo sensors and actuators connected in a closed-loop architecture with PD feedback is performed; the effects of feedback gain, sensor/actuators location and thicknesses are investigated to show the capability to reduce the dynamic environment transmitted to the satellite.
pH Self-Controlling Induced by Tourmaline
Authors: Nishi Yoshitake , Yazawa Ayumu , Oguri Kazuya , Kanazaki Fumio , Kaneko Toshio
Published: August 2009

The effect of tourmaline on pH controlling is investigated. The hydrogen ion concentration tremendously decreases for 1 h. The concentration approaches 10-7 mol/l at infinite time. On the other hand, the materials intelligence (Ih) has been suggested. If the fh value is 50, we can determine the Ih value [Ih (50)] for tourmaline. The Ih (50) and Pr values are 0.38 and 0.70 for tourmaline.
Characterization of Transfer Functions for Piezoceramic and Conventional Transducers
Authors: Wang Bor-Tsuen
Published: August 2009

This paper analytically derives the transfer functions for piezoceramic and conventional tranducers and characterizes their relationships in terms of frequency response function (FRF) and modal parameters such as natural frequencies, damping ratios, and mode shapes. The FRFS between accelerometer/point force actuator, accelerometer/PZT actuator, PVDF sensor/point force actuator, and PVDF sensor/PZT actuator are determined, respectively. Those FRFs are expressed in conventional modal model format which can clearly get insight of physical meaning of modal parameters. In particular, the mode shapes of accelerometer, point force actuator, PVDF sensor, and PZT actuator are identified and are proportional to the displacement mode shapes. The point and transfer FRFs are then studied to characterize their properties for either pair of transducer applications. This work leads to the basis for active structural vibration and acoustic control and also draws on ideas for applications of smart structural testing to system identification and diagnosis.
Material Damping Analysis of Smart Hybrid Composite Laminated Plate Structures
Authors: Baburaj Vijayan , Matsuzaki Yuji
Published: August 2009

Material damping analysis of a generally laminated smart hybrid composite plate has been presented in this paper. The present analytical formulation is an integrated micro-macromechanical method. Analytical equations derived at the lamina level together with a classical laminated thin plate theory predict the equivalent material specific damping capacity (SDC) of a general smart hybrid composite laminated plate structure. The micro-niechanical equations based on the mechanics of material have been used for the calculation of the elastic stiffness and SDC ot an intraply hybrid composite lamina. Present objective is mainly to get a first hand information on the basic material damping behavior of hybrid composite laminate. Therefore, numerical studies have been carried out for a typical shape memory alloy (SMA) smart composite laminated plate model. The effects of the laminate fiber orientaton and the SMA volume fraction on the SDC and natural frequencies of the laminate were evaluated.
A One-Dimensional Model of a Shape Memory Alloy Fiber Reinforced Aluminum Metal Matrix Composite
Authors: Armstrong William D.
Published: August 2009

A one-dimensional model of a shape memory alloy fiber reinforced aluminum metal matrix composite is developed based on a linearized shape memory alloy constitutive model. The requirements of stress equilibrium and strain compatibility within the composite couple the constitutive variables of the shape memory alloy reinforcement. The shape memory alloy reinforcement's state trajectory resulting from a particular external thermal-mechanical process is therefore sensitive to the external process, the constitutive properties of the composite matrix, and fiber volume fraction. Three distinct thermal-mechanical processes are treated in this paper; the first is an isothermal tensile loading-unloading process at the stress free martensitic transformation start temperature; the second is an external stress free thermal process to a temperature above that required for the shape memory alloy reverse transformation; and, the final process is an isothermal loading at the thermal process finish temperature. The model predicts that the composite will exhibit a large longitudinal compressive strain during the heating process, and will retain a large matrix residual compressive stress at the end of the heating process. The model also predicts that the composite elevated temperature flow strength will be significantly higher than that of the unreinforced matrix alloy.
A Comparative Study of AC and DC Electrorheological Material Based Adaptive Structures in Small Amplitude Vibration
Authors: Shiang Andy H. , Coulter John P.
Published: August 2009

The present investigation focused on the controllability and reliability of AC and DC electrorheological (ER) materials based adaptive beams. The mechanical and rheological reliability of such adaptive structures was studied over an extended time period. Modal vibration frequencies exhibited relatively stable behavior over time, while modal loss factors were observed to vary significantly. Significant structural stiffening in response to electric field was observed with the DC ER material, while damping dominated the changes observed with the AC ER material. Oscillatory shear experiments with the two materials provided insight into the cause of the observed differences between AC and DC material based structural response. At small strains both ER materials behaved in a nonlinear viscoelastic fashion. The relative contributions of nonlinear loss and storage moduli were found to cause the observed differences in the performance of these adaptive structures. The structural time response upon the application or removal of electric field was also studied. Both AC and DC structures responded rapidly to the application of electric field. For the case of electric field removal, however, it was found that the field strength and application time. ER material type. and structural excitation amplitude all influenced response time.
Tendon Control System for Active Shape Control of Flexible Space Structures
Authors: Okubo Hiroshi , Komatsu Nobuo , Tsumura Toshihiro
Published: August 2009

Large space structures are very flexible and are easily deformed due to any disturbances in the space environment. This paper proposes a tendon control system for the shape control of flexible space structures and presents methods of determining the structural deflections accurately and applying control forces effectively to restore the desired shape. The problem of active shape control consists of: (1) estimating the deformed shape of a flexible structure from multi-point spatially distributed measurement of the structural deflections, and (2) restoring the desired shape by means of control actuators installed on the structure. This paper develops the estimation and control designs using an infinite-dimensional approach, where the necessary finite element truncation and approximation are introduced after solving the estimation problem. The proposed shape estimation algorithm determines the deformed shape of the structure subjected to unknown disturbance forces from multi-point spatially distributed measurement of the structural deflections. Active static control force is determined so that the integrated restoration error may be minimized. The control design is based on the least squares estimation algorithm. This paper also studies the optimal actuator location that minimizes the restoration errors. The method is applied to an experimental tendon control system for a highly flexible beam. The results of numerical simulations are given for demonstrating the feasibility of the present estimation and control method and for investigating the optimal actuator location.
Electrorheological Effect of Reducing the Suspension Viscosity in Laminar Flows below the Viscosity of Anisotropic Dispersive Medium
Authors: Taran E. Yu , Pridatchenko Yu V. , Selezov I. T. , Taran D. E.
Published: August 2009

Electrorheological features of a dilute suspension in Ericksen anisotropic fluid are analyzed on the basis of rheological constitutive equations obtained in the present paper. It is assumed that suspended particles possess a zero bouyancy and constant dipole moment, the anisotropic dispersive medium of suspension is electrically neutral. As a hydrodynamic model of suspended particles, the uniaxial dumbbell is used. The sizes of suspended particles are assumed to be much more than elements of microstructure which are responsible for anisotropy of dispersive medium.

The rheological equations of suspension under consideration are obtained on the basis of the structure-phenomenological approach. The rheological behavior is suspension is investigated in a simple shear flow in the presence of external electric field. It is shown that the suspension behaves itself as anisotropic non-Newtonian fluid. The possibility of reducing the effective viscosity of suspension of laminar shear flows below the value of effective viscosity of anisotropic dispersive medium is predicted theoretically. It takes place at certain orientation of suspension particles of suspension under action of the external stationary electric field and the hydrodynamic forces.

The result obtained can be used for studying the suspension in liquid crystals.
Investigation into the Use of Liquid Crystalline Materials in Electrorheological Fluids
Authors: Lacey D. , Malins C. , Taylor P. M. , Hosseini-Sianaki A. , Varley C. J.
Published: August 2009

The ER activity of a number of ER fluids incorporating liquid crystalline (LC) and non-LC materials have been measured using a laminar-flow shear cell. The results from this static study are presented and clearly show that the unique self-organising and anisotropic physical properties of the LC materials contribute greatly to the ER activity of LC based ER fluids. A more in-depth evaluation was then carried out on a LC based ER fluid which involved measurements of the steady state behaviour, under various operational conditions, and the results compared with those from two conventional silicone based fluids. From this dynamic study it was found that within the shear rates tested, for an electric field strength above 1 kV mmn' there existed a linear relationship, culminating in a shear stress of 12 kPa at an electric field strength of 4 kV mmi'. The unique property of the shear stress increasing with increase in the shear rate makes LC based ER fluids an exciting area for further research and this could be of considerable importance in their use in a variety of control systems.
Quasistatic Efficiency of a Concentric ER Clutch
Authors: Oravsky V.
Published: August 2009

An application of electrorheological (ER) fluid in ER clutch is considered. The clutch is embedded in a broader system with a driving machine on one side and a loading machine (brake) on the other. The quasistatic model of the system at a constant load and speed is described and solved in a dimensionless form.

Efficiency of ER clutch is determined as the ratio of the output and input powers and consecutively analyzed in the space of model parameters. A special sensitivity analysis for many thousands of combinations of parameters (in their possible ranges) is performed and statistically evaluated.

For some combinations of parameters and some arrangements of the system, efficiency can be greater than one due to additional energy originating from ER fluid. In such cases, more refined energy balance and definition of efficiency are needed.
Dynamic Magneto-Optical Response of Ferronematic Liquid Crystals
Authors: Raikher Yuri L. , Stepanov Victor I.
Published: August 2009

We study the time-dependent orientational response of a nematic liquid crystal doped with single-domain ferromagnetic particles. A set of coupled macroscopic equations describing evolution of the director texture, magnetization distribution and concentration of the particles under the change of the external field is derived. For the case of a plane layer, expressions for the main rela; .ation rates are obtained and analyzed.
Nonlinear Parameter Identification of an Electro-Rheological Fluid Damper
Authors: Mui G. , Russell D. L. , Wong J. Y.
Published: August 2009

Parameters for a nonlinear model of an electro-rheological (ER) damper were identified from experimental data. The ER fluid used in the test damper was composed of zeolite particles with diameters less than 10 microns suspended in 20 centistoke silicon oil. Motion of the damper piston forced the fluid to flow through annular gaps between three concentric cylindrical electrodes. Experiments were performed on the damper by using a fatigue testing machine made by Testline Mechanical Test Systems to provide a controlled movement of the damper. The measured data included the damper force, the piston displacement as well as the voltage applied to the damper electrodes and the resulting current. The parameters were identified using a quasi-linearization technique which has been found suitable for similar nonlinear parameter model identification problems. The model used in the study included the effects of fluid inertia, as well as viscous and Coulomb friction components. Results of the identification indicate that, although the parameters generally were found to vary from one oscillation cycle to the next, average parameters were able to predict the force in the damper as a function of damper motion and the applied voltage. Some evidence suggests that the predictive capabilities of future models may be improved by adding fluid compressibility and hysteresis to the model.
Nonlinear Optical Study of ER Fluids
Authors: Wu J. Y. , Shen L. K. , Zhou L. W.
Published: August 2009

A nonlinear optical method is used to study the mechanism of ER fluids. The fluid used in this study is diatomite dispersed in transformer oil. Because of the non-homogeneity of the ER fluid, second harmonic generation (SHG) powder technique is employed. Electric field induced SHG signal of the fluid has been found and the response time of the fluid has been measured. Two kinds of polarization are deduced to contribute to the ER effect of the sample at different periods. A two-stage process of ER effect is adapted to explain the experiment results.
Magnetorheological Fluid-Based Seal
Authors: Kordonski W. I. , Gorodkin S. R.
Published: August 2009

The present experimental work has been done to study the characteristics of the simplest one-step magnetofluid seal (MFS) of the rotary shaft in which the MR fluid (MRF) serves as a sealing medium.

The experiments show that the characteristics of the MRF-based seal differ very much from those of the ferrofluid (FF)-based one. In the static regime (stationary shaft), all other things being equal, the MRF holds an approximately three-fold pressure drop. The distinguishing feature of the functioning of such a seal is revealed and lies both in sharply elevating the pressure drop in the dynamic regime (rotary shaft) as against the static one and in having a maximum on the dependence of the pressure drop on the shaft rotation speed. In this regime, the MRF efficiency grows almost by the order of magnitude. However, the seal under study has an increased friction torque due to the growth of the shear stress of the MRF volume subject to shearing in the magnetic field.
Development of an Artificial Skin Ridge for Pattern Recognition
Authors: Tseng C. I. , Liou W. J. , Lee H. J.
Published: August 2009

This paper describes a sensing technique which utilizes artificial neural networks and a distributed sensor. The concept resembles the manner in which humans use their fingertips to touch objects, and subsequently use their brains to classify and recognize images detected. There are three major components of the designed sensor: a compliant skin is made of rubber with wedge-shaped ridge, an energy transducer which is a piezoelectric polyvinyledene fluoride film, and neural networks which are used to characterize signals through a learning process. The backpropagation is used as a learning rule, thus, learning required a set of input patterns each paired with a desired output pattern. The objective for the networks is to learn and memorize, after proper training, in order to reproduce desired outputs. Experimental results show that the sensor with artificial neural nets is very effective at recognizing Braille characters including SIX, SEVEN, EIGHT, UP, DOWN, LEFT, and RIGHT.
Using Energy Methods to Derive Beam Finite Elements Incorporating Piezoelectric Materials
Authors: Carpenter Michael J.
Published: August 2009

We apply the principle of virtual work to derive the equations of motion for arbitrarily shaped linear piezoelectric materials which are either embedded in or perfectly bonded to the surface of an elastic substructure. Using an Euler-Bernoulli strain model, the equations of motion are subsequently specialized to obtain finite elements for an elastic beam incorporating piezoelectric materials. This formulation leads to a general consistent electrical stiffness matrix that characterizes the electromechanical coupling of the piezoelectric material; thus a finite element for any particular beam cross section geometry can be obtained by computing the areas of cross sections of the substructure and the piezoelectric material and the first and second moments of their cross sections. Actuator finite elements are discussed for cases where the piezoelectric material is connected to a voltage source and a current source. We also discuss sensor finite elements when the piezoelectric is connected to two types of amplifying circuits to measure the induced electric potential across the piezoelectric material. Several examples are presented to compare the results in this paper to the results of other researchers and to ascertain the numerical properties of the finite element for a specific example.
Detection of Impact Location and Magnitude for Isotropic Plates Using Neural Networks
Authors: Jones Richard T. , Sirkis James S. , Friebele E. J.
Published: August 2009

A neural network-based method of determining the location and magnitude of trans-verse impact events on isotropic plates is investigated experimentally. Time data from four sensors mounted in the corners of an aluminum plate was processed to provide inputs for two backpropaga-tion neural networks. The first neural network was responsible for detecting impact location. After 1 million iterations of training, this neural network was able to locate impacts with an average RMS error of 1.55 radial centimeters on a 58.5 centimeter by 36.8 centimeter (23 inch by 14.5 inch) fully-clamped plate. The second neural network was responsible for impact magnitude detection. This neural network was able to determine the impact magnitude with an average of 13.8% error.
Distributed Control of Laminated Beams: Timoshenko Theory vs. Euler-Bernoulli Theory
Authors: Aldraihem Osama J. , Wetherhold Robert C. , Singh Tarunraj
Published: August 2009

In this paper, the governing equations and boundary conditions of laminated beamlike components of smart structures are reviewed. Sensor and actuator layers are included in the beam so as to facilitate vibration suppression. Two mathematical models, namely the shear-deformable (Timoshenko) model and the shear-indeformable (Euler-Bernoulli) model, are presented. The differential equations of the continuous system are approximated by utilizing finite element techniques for both models. A cantilever laminated beam with and without a tip mass is investigated to assess the validity and the accuracy of the two models when used for vibration suppression. Comparison between the two models is presented to show the advantages and the limitations of each of the models. Since the Timoshenko beam theory is higher order than the Euler Bernoulli theory, it is known to be superior in predicting the transient response of the beam. The superiority of the Timoshenko model is more pronounced for beams with a low aspect ratio. It is shown that use of an Euler-Bernoulli based controller to suppress beam vibration can lead to instability caused by the inadvertent excitation of unmodelled modes.
A Neural Network Approach to Zinc and Copper Interferences in Potentiometric Stripping Analysis
Authors: Chow Christopher W. K. , Davey David E. , Mulcahy Dennis E.
Published: August 2009

Zinc and copper are two elements which mutually interfere with each other in stripping analysis. The cause is the formation of a Zn-Cu intermetallic compound in the mercury film, which affects both Cu and Zn analyses. A backward error propagation artificial neural network has been applied in a novel approach for the determination of zinc in the presence of copper using potentiometric stripping analysis. This performed well in determining the correct zinc concentration in the sample when provided with the stripping times of zinc and copper and the copper concentration (determined by shifting the plating potential to a lower value to prevent the zinc being plated onto the mercury film electrode). The unknown zinc concentration was determined following an initial period of network exposure to a set of experimental data, which were used as examples of the required input/output data mapping.
Analysis of Trigger Line Models for Shape Memory Hysteresis Based on Dynamic Testing
Authors: Thomson Peter , Balas Gary J. , Leo Perry H.
Published: August 2009

Trigger line models for the behaviour within the pseudoelastic hysteresis of shape memory alloys are considered in the analysis of the dynamic response of a cantilevered beam constrained by shape memory wires. Quantitative results of damping and shift in natural frequencies of the structure are presented. The results are compared to theoretical predictions of the effect of inner hysteresis loops on structural dynamics. The comparison suggests that there may be two trigger lines, one for loading and one for unloading, within the hysteresis loop.
A New Design for a Rotatory Joint Actuator Made with a Shape Memory Alloy Contractile Wire
Authors: Wang Guoping , Shahinpoor Mohsen
Published: August 2009

Presented in this paper is a new design approach for a bias force type of shape memory alloy (SMA) rotatory joint actuator, which uses an SMA contractile wire as an actuating element. A quasi-static analysis is assumed and a coefficient of variation of bias stress, fi, is introduced to give a quantitative expression of a variation of bias stress in terms of a working stress range of the SMA wire. The effects of this coefficient on the load efficiency and the bias spring's parameters of a bias force SMA rotatory joint actuator are described. The use of this coefficient,B leads to a simple design procedure. An example design case is carried out by using this design procedure to demonstrate its usefulness. This paper does not cover an analysis of thermal response history of a designed actuator. The design approach described in this paper will provide a practical and convenient method for use in design of bias force SMA rotatory joint actuators for design requirements of maximum loads and maximum displacements.
Computational Methods for a Curved Beam with Piezoceramic Patches
Authors: Banks H. T. , Zhang Y.
Published: August 2009

We develop a computational scheme to approximate the solutions of a mathematical model that describes the vibrations of a curved beam structure. The physical model also includes pairs of piezoceramic patches that can be viewed either as passive devices, changing only the structural properties of the beam, or as active devices used to control vibrations of the beam. As part of our numerical experiments, we compare schemes with a method that employs hybrid B-spline basis elements and a method that employs just one family of B-spline basis elements. We calculate the first four fundamental frequencies and mode shapes of the structure, and we simulate patch-activated vibrations. Finally, we devote a section to investigation of locking phenomena which have been reported for some shell problems.
An Impedance Method for Dynamic Analysis of Active Material Systems
Authors: Liang C. , Sun F. P. , Rogers C. A.
Published: August 2009

This paper describes a new approach to analyzing the dynamic response of active material systems with integrated induced strain actuators, including piezoelectric, electrostrictive, and magnetostrictive actuators. This approach, referred to as the impedance method, has many advantages compared with the conventional static approach and the dynamic finite element approach, such as pin force models and consistent beam and plate models. The impedance approach is presented and described using a simple example, a PZT actuator-driven one-degree-of-freedom spring-massdamper system, to demonstrate its ability to capture the physics of adaptive material systems, which is the impedance match between various active components and host-structures, and its utility and importance by means of an experimental example and a numerical case study.

The conventional static and dynamic finite element approaches are briefly summarized. The impedance methodology is then discussed in comparison with the static approach. The basic elements of the impedance method, i.e., the structural impedance corresponding to actuator loading and the dynamic output characteristics of PZT actuators, are addressed. The advantages of using the impedance approach over conventional approaches are discussed using a simple numerical example. A comparison of the impedance method with the static and the dynamic finite element approaches are provided at the conclusion of this paper.
Transient Electro-Mechanics of Piezoelectric Actuator-Driven Active Mechanical Systems
Authors: Liang C. , Rogers C. A.
Published: August 2009

This paper presents a theoretical model to determine the transient electro-mechanical response of active structures driven by piezoelectric (PZT) actuators. The solution is expressed in terms of actuator and structural mechanical impedances, which are the steady state frequency domain dynamic properties and can be characterized theoretically or experimentally. Theoretical case studies have also been presented using a simple example of a PZT actuator-driven one-degree-of-freedom spring-mass-damper system. The solution of the transient response includes the transient electrical current passing through the PZT actuator and the mechanical response of the system (displacement and force). The solution technique may also be applied to active structures driven by other types of induced strain actuators, including electrostrictive and magnetostrictive actuators.
Finite Element Analysis of Rainbow Ceramics
Authors: Li Guang , Furman Eugene , Haertling Gene H.
Published: August 2009

The finite element method has been utilized to analyze the processing and performance of the newly developed Rainbow (Reduced And INternally Biased Oxide Wafer) ceramic actuators. A Rainbow is produced by a special chemical reduction process to form a dome-shaped, stress-biased structure which delivers a large field-induced displacement while attaining moderate load-bearing capability. The creation of the domed structure and accompanying internal stress by the reduction process is simulated by considering a Rainbow as a two-layer heterogeneous circular plate and allowing it to cool down from the reduction temperature to room temperature. Based on the derived domed structure, the Rainbow performance including electric field-induced displacements and resonant characteristics is modeled. Modeled dome curvature, internal stress, and electromechanical characteristics of the Rainbow ceramic are discussed with respect to material properties and geometrical parameters. Comparisons between the modeling results and the experimental data obtained from the Rainbow samples made with PLZT ceramics are presented. A good agreement was exhibited between the modeling predictions and the experimental measurements for the dome curvature and internal stress distribution, but appreciable disparities were observed in the electromechanical properties. The results imply that the internal stress should have a strong influence on the Rainbow's electromechanical performance.
Equations for Elastic Plates with Partially Electroded Piezoelectric Actuators in Flexure with Shear Deformation and Rotatory Inertia
Authors: Yang J. S.
Published: August 2009

A system of two-dimensional equations for the flexural motion of an elastic plate with both electroded and unelectroded portions of piezoelectric actuators attached to the top and bottom surfaces are derived from existing equations of thin elastic and piezoelectric plates by satisfying the actuator-plate interface conditions. In the derivation, the piezoelectric actuators are assumed to be very thin compared to the elastic plate and are treated as films which are in extensional motion but do not resist bending. The unelectroded portions of the piezoelectric actuators have the effect of reducing the shear stress concentration near the edges of the actuators. These equations are generalizations of an earlier system of equations in the literature in that the elastic plate is governed by the Reissner Mindlin theory of flexure with shear deformation and rotatory inertia. Therefore they can be used in cases when the elastic plate is not very thin. The equations obtained are of second order and are suitable for finite element implementation.
Dynamic Effects of Piezoelectric Actuators on the Vibrational Response of a Plate
Authors: Charette F. , Berry A. , Guigou C.
Published: August 2009

This paper presents an analytical model and an experimental study for the response of plates actuated by piezoceramic elements. The variational approach with Hamilton's principle is used to develop the analytical model. This formulation, which is energy based, allows to consider any boundary conditions at the edges of the plate and to take into account the dynamic effects (mass loading and stiffness) of the piezoelectric actuators on the plate response. The ratio between the piezoelectric actuator mass and the plate mass considered in this work is small (less than 0.5%). Nevertheless, the model and the experiments demonstrate that the dynamic coupling between the piezoelectric actuators and the plate slightly modifies the plate modes. These structural modifications are apparent in some vibrational indicators, such as the displacement at the center of the plate and the volume displacement induced by the plate.
Vibration Control of Stiff Beams and Plates Using Structurally Integrated PZT Stack Actuators
Authors: Redmond Jim , Barney Pat
Published: August 2009

An actuation technique suitable for controlling bending vibrations in thick beams and plates is described. This work is motivated by vibration problems encountered in manufacturing that require greater control authority than can be obtained using surface mounted PZT patches or PVDF films. Instead, PZT stack actuators mounted in material cutouts are used to induce bending moments in the host structure. Experimental results are provided for the case of a cantilevered bar and a lithography platen used in the manufacture of integrated circuits. Good coupling between the extensional motion of the actuators and the bending deformation of the host structures is illustrated, and significant increases in first mode damping are achieved in both examples using a positive position feedback compensator.
Quasi-Static Behavior of Individual C-Block Piezoelectric Actuators
Authors: Moskalik Andrew J. , Brei Diann
Published: August 2009

Most piezoelectric actuators used in smart structure applications are either stiff stacks which produce high forces and small deflections, or compliant benders which produce large deflections and small forces. This leaves a mid-range gap in actuator performance in which many applications operate. A new class of solid state actuators, known as C-blocks, has been developed as a mid-range actuator. A C-block is a semicircular composite bender actuated with piezoelectric layers. It can be combined in series and/or parallel to increase actuator deflection and/or force. A simple, linear analytical model for the quasi-static force-deflection behavior of a generic individual C-block is presented in this paper. This model can be used to determine the relationship between force and deflection, as well as the free deflection, blocking force, actuator stiffness, and maximum energy transferable to the actuated system. This model was experimentally verified with three case studies: PZT-8 and PZT-5H ceramic unimorphs; PVdF polymeric bimorphs; and four-layer PVdF polymeric multimorphs. The results from these case studies confirm that C-blocks are over six times stiffer, and generate over two-and-a-half times more force than a comparable straight bender.
Closed-Loop Feedback Control of Magnetically-Activated Gels
Authors: Mitwalli Ahmed H. , Denison Timothy A. , Jackson Deron K. , Leeb Steven B. , Tanaka Toyoichi
Published: August 2009

Polymer gels that exhibit a change in volume in response to a small change in an environmental parameter such as temperature have been fabricated and studied for several decades. We have developed gels that change volume in response to an applied alternating magnetic field. These gels could serve as actuators in servomechanisms. This paper presents practical techniques for using closed-loop feedback to control the position of magnetically-triggered polymer gels. Experimental results are presented that demonstrate position control of two different types of magneticallytriggered gels using prototype power electronic drives.
Application of Dual Kriging to the Construction of a General Phenomenological Material Law for Shape Memory Alloys
Authors: Terriault P. , Meunier M. -A. , Trochu F.
Published: August 2009

A large number of applications could benefit from the remarkable properties of shape memory alloys; but up to now, a relatively limited number have been brought to the market. This can be attributed, in part, to the lack of numerical tools dedicated to the computer aided design of shape memory devices. The development of a general material law is the first important step before reliable design calculations can be carried out. This paper presents a new phenomenological constitutive law based on dual kriging, which is a powerful mathematical tool used here as an interpolation method. The model was initially developed for a particular and limited purpose, namely, to simulate the macroscopic behavior of simple shape memory devices. From a few isothermal experimental forcedeflection curves at different temperatures, two surfaces are constructed which describe the loading and unloading behavior of the device.The response of the material subjected to complex thermomechanical loadings is calculated by successive interpolations on these surfaces via dual kriging. For hysteretic subcycles, the response is calculated through the volume delimited by the two surfaces in such a way that any recursive thermomechanical subcycles can be simulated. This methodology yields a uniaxial material law for shape memory alloys that includes in a single formulation superelasticity, pseudo-plasticity and shape memory effect. Preliminary validations on a set of simple examples show the potential of this approach.
Fiber Optic Condition Monitoring during a Full Scale Destructive Bridge Test
Authors: StorΦy Helge , SÆther Joar , Johannessen Kjetil
Published: August 2009

Fiber optic sensors were used to monitor structural parameters during a destructive bridge test. A system composed of four different types of fiber optic sensors was used to demonstrate versatility and possible completeness for these type of measurements using fiber optic sensors. The fiber optic sensors were monitored continuously during the test using a single control unit. Local strain measurements on the reinforcing bars were conducted using fiber optic Bragg grating sensors. A new technique employing both current and temperature tuning of a DFB (Distributed Feedback) laser to interrogate gratings was developed, showing good correspondence with resistance strain gauges. This sensor conducted the only strain measurements during and after the failure of the bridge, since all expensive control electronics could be operated from a safe distance. A Bragg grating laser sensor system was also used, with a laser cavity of 40 m using standard connectors. The system was well behaved and the measurements corresponded well with resistance strain gauges. A fiber optic polarimetric sensor measured displacements over 2.5 m at the bridge surface. The measurements were comparable to conventional extensiometer measurements at the same location. Cracking of the bridge surface was monitored by studying reflection and transmission characteristics of optical fibers glued to the surface. Although less cracking occurred than was expected, both transmission loss and OTDR (Optical Time Domain Reflectometry) reflection measurements successfully detected cracking of the bridge surface. The most severe practical problem was unintentional fiber breaks caused by personnel not accustomed to using fiber optics.
Experimental Testing and Analtical Modeling of Semi-Active Fluid Dampers for Seismic Protection
Authors: Symans Michael D. , Constantinou Michael C.
Published: August 2009

The development, experimental testing, and analytical modeling of an intelligent seismic response control system is described in this paper. The control system is in the form of semiactive fluid damping devices which may be installed within the lateral bracing system of buildings or as part of a seismic isolation system for bridges or buildings. The dampers have mechanical properties which can be modified through a closed-loop feedback control system which utilizes the measured earthquake excitation and/or the response of the structural system. Further, the dampers exhibit fail-safe characteristics in that, in the event of failure to operate as semi-active devices, the dampers convert to passive high-damping devices. The dampers were extensively tested to determine the mechanical properties and the dynamic behavior of the devices. Furthermore, mathematical models for describing the damper behavior were developed and utilized for analytically predicting experimental results.
Application of Forced Electrification for Preparation of Complex Particles
Authors: Dan Takehiro , Egashira Mitsuru , Kyono Junro , Fudouzi Hiroshi , Shinya Norio
Published: August 2009

The purposes of the present work are to describe the importance of the application of forced electrification on complex particle preparation and to develop new materials with multiple functions by combining two kinds of particles electrified reciprocally. This paper reports a preparation method and the positive temperature coefficient of resistivity (PTCR) characteristics of composites consisting of semiconductive BaTiO3 particles and metallic indium powder.

The forced electrification technique was applied to a complex particle preparation process and confirmed to be effective as follows:

1. A vibrating cylindrical electrode can force-electrify metal, semiconductor and insulator particles with positive or negative charges.

2. When two kinds of particles electrified reciprocally are mixed in the same region at the same time, complex particles can be produced by the electrostatically attractive force working between them.

3. Indium-semiconductive BaTiO3 complex particles made with this processing offer a new PTCR material which can be used in arbitrary shapes by simple packing. This behavior cannot be accomplished by the conventionally sintered PTCR materials.
Vibration Control through Passive Constrained Layer Damping and Active Control
Authors: Lam Margaretha J. , Inman Daniel J. , Saunders William R.
Published: August 2009

To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached, creating a passive constrained layer damping (PCLD) treatment. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active and PCLD element will be investigated. Two new hybrid variations will be introduced. A Ritz-Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the Golla-Hughes-McTavish (GHM) method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it will be shown that hybrid treatment is capable of lower control effort with more inherent damping, and is therefore a better approach to suppressing vibration than ACLD.
Control of Sound Transmission through a Convected Fluid Loaded Plate with Piezoelectric Sensoriactuators
Authors: Frampton Kenneth D. , Clark Robert L.
Published: August 2009

The use of piezoceramic transducers to control sound transmission through a convected fluid loaded plate is analytically investigated. The investigated system consists of an elastic plate subjected to convected fluid loading (i.e., aeroelasticity) on one side and coupled to an otherwise rigid acoustic enclosure on the other side. The control of sound transmission from the convected fluid side to the cavity is achieved by applying constant gain output feedback using piezoceramic transducers as sensoriactuators. A sensoriactuator is a single transducer which simultaneously acts as a sensor and actuator, thus providing significant stability and robustness advantages. Results demonstrate that such a control system can significantly reduce the transmitted sound. However, variations in the velocity of the convected fluid can reduce the effectiveness of such a control system.