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Total 266 records

    Crack detection in underground pipelines using piezoelectric sensors

    , Article Advanced Science Letters ; Volume 19, Issue 3 , 2013 , Pages 770-774 ; 19366612 (ISSN) Nozarian, M. M ; Adeldost, H ; Zabihollah, A ; Sharif University of Technology
    2013
    Abstract
    Regarding the structural health monitoring of pipelines, early detection of cracks may be one of the possible ways to prevent future failures. Among the detection methods which have been known, one is to measure the vibration signals generated due to the hydraulics of pipe. This article discusses application of thin film piezo sensors mounted directly on the pipe. The vibration induced strain is transuded into electric voltage by the piezoelectric sensor. The recorded signals are used for PSD analysis which indicates that this method can be used as an accurate and cost effective detection. Moreover the promising results from the respective experiments on pipes indicated that second natural... 

    Frequency domain identification of a tapered beam embedded by piezoelectric layer

    , Article 2016 International Conference on Advanced Mechatronic Systems, ICAMechS 2016, 30 November 2016 through 3 December 2016 ; 2017 , Pages 312-317 ; 23250682 (ISSN); 9781509053469 (ISBN) Banazadeh, A ; Ahranjani, F. F ; Kamankesh, Z ; Sharif University of Technology
    IEEE Computer Society  2017
    Abstract
    This study is conducted aiming to identify the dynamics of a tapered beam, embedded by piezoelectric layer. Narrowing the tip of the beam equipped with piezoelectric patches leads to optimize the output power after excitation by the frequency sweep input. An accelerometer is installed on the beam base, which measures the acceleration that is applied to the system. Piezoelectric sensors also measure the generated voltage. The experimental test data is handled through CIFER software, using Fourier transform and Bode plot in the frequency domain, to obtain appropriate transfer functions. MATLAB is used for nonlinear simulation and validation of discrete transfer functions by a set of data that... 

    Active performance optimization of cantilever piezoelectric energy harvester

    , Article ASME 2014 12th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2014 ; Vol. 2 , 2014 ; ISBN: 9780791845844 Anbarani, M. T ; Alasty, A ; Sharif University of Technology
    Abstract
    A Piezoelectric Energy Harvester (PEH) of cantilever beam type is developed to optimize the generated power by means of active control of moment of inertia of the beam. Distributed parameter equations of vibration of the beam are developed. Then the electromechanical response of the piezoelectric actuator is discussed. The harvester configuration is then described and it is shown that such a configuration can avoid the drastic power drop in presence of uncertainty around resonance frequency by applying voltage to the piezoelectric actuator. Finally the proposed harvester output power working frequency span is compared to conventional methods to show that the significant performance... 

    Monitoring pipeline vibration due to cavitation through an orifice by piezoelectric sensor

    , Article Advanced Materials Research ; Volume 403-408 , 2012 , Pages 3418-3423 ; 10226680 (ISSN) ; 9783037853122 (ISBN) Rad, F. P ; Zabihollah, A ; Sharif University of Technology
    Abstract
    Pipelines are one of the most important and efficient ways for transporting energy like water, gas, oil and etc. between different places all across the world. As these pipelines are located in different conditions and situations, they are all sensitive to a wide variety of damages like vibration, so monitoring their structural behavior is an essential task. Monitoring pipeline vibration caused by cavitation through an orifice by a piezoelectric sensor is presented in this paper  

    Modeling and simulation of graspers force in minimally invasive surgery

    , Article 2009 International Association of Computer Science and Information Technology - Spring Conference, IACSIT-SC 2009, Singapore, 17 April 2009 through 20 April 2009 ; 2009 , Pages 475-479 ; 9780769536538 (ISBN) Hortamani, R ; Zabihollah, A ; Sharif University of Technology
    2009
    Abstract
    In Minimally Invasive Surgery (MIS) the operation is performed through introducing surgery instruments, graspers, scissor into the body. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum by surgeon and to measure the transmitted response to the tissue/organ. © 2009 IEEE  

    Electrical equivalent circuit of multi-mode flexible beams with piezoelectric elements

    , Article Journal of Intelligent Material Systems and Structures ; Volume 19, Issue 5 , 2008 , Pages 621-627 ; 1045389X (ISSN) Saghafi, M ; Meghdari, A ; Sharif University of Technology
    2008
    Abstract
    Surface mounted piezoelectric sensors and actuators on elastic structures are often connected to electrical networks. The coupled equations of motion of the elastic structure with piezoelectric elements are already well known. However, due to complex behavior of some electrical elements in the electrical network, it is not an easy task to obtain the integrated equations of the whole system. A good remedy for this problem is to take advantage of an equivalent electrical circuit (EEC) representation of the mechanical part, leading the entire system to be represented as an electrical circuit. In this study, the authors propose a new method for constructing the EEC. This method is based upon the... 

    Nonlinear modeling of piezoelectric layered beams

    , Article Active and Passive Smart Structures and Integrated Systems 2007, San Diego, CA, 19 March 2007 through 22 March 2007 ; Volume 6525 , 2007 ; 0277786X (ISSN) Saghafi, M ; Jalili, N ; Meghdari, A ; Sharif University of Technology
    2007
    Abstract
    The dynamic equations of piezoelectric benders are studied in this paper, considering nonlinear behavior of piezoceramics. A second order approximation of constitutive equations of piezoceramics is used to account for reversible nonlinearities. Transversal and longitudinal deflections at the tip of the beam and the blocking force as well as sensor equations (output charge as a function of external loads) are obtained under static conditions. The static equations are then used to construct a linear dynamic model for actuation. A Bouc-Wen type hysteresis model is employed in order to account for the irreversible nonlinearities. The final equation of motion is in the form of well-known Hill's... 

    Synthesis and Properties of PZT-PCN Ceramics

    , M.Sc. Thesis Sharif University of Technology keshavarzi, Mostafa (Author) ; Nemati, Ali (Supervisor) ; Seyyed Reyhani, Morteza (Supervisor)
    Abstract
    Today, base lead piezoelectrics are the center of attention due to their very good electrical properties, and low cost of production. Among these ceramics are PZT which is a combination of Pb(ZrxTi1-x)O3 and PCN which is a combination of Pb(CoxNb1-x)O3. PZT is a normal piezoelectric whose dielectric properties would be improved if relaxor is added. PCN is ferroelectric with perovskite structure and curie temperature -27℃ which is known as a relaxor with high constant dielectric properties. In this research, adding PCN to PZT was done by sol-gel seeding method. Calcination at a temperature of 900℃ was causing the creation of single-phase perovskite powder. After that, conventional sintering... 

    A piezoelectric medium containing a cylindrical inhomogeneity: Role of electric capacitors and mechanical imperfections

    , Article International Journal of Solids and Structures ; Volume 44, Issue 20 , 2007 , Pages 6361-6381 ; 00207683 (ISSN) Mohammadi Shodja, H ; Tabatabaei, S. M ; Kamali, M. T ; Sharif University of Technology
    2007
    Abstract
    Often, during fabrication processes of fiber-matrix composites, the pertinent interface may be made imperfectly bonded either deliberately or undesirably. The effect of electric capacitors and mechanical imperfections on the electro-mechanical fields associated with an anisotropic piezoelectric matrix containing a cylindrical inhomogeneity made of a different anisotropic piezoelectric material is of interest. In fact the interface imperfection condition presented in this paper is quite general, in the sense that any combination of mechanical and electrical imperfections may exist. The interface electrical imperfection is mimicked by the electric capacitors. The capacity of the capacitors is... 

    Displacement potentials for functionally graded piezoelectric solids

    , Article Applied Mathematical Modelling ; Volume 52 , 2017 , Pages 458-469 ; 0307904X (ISSN) Samea, P ; Eskandari, M ; Ahmadi, S. F ; Sharif University of Technology
    Abstract
    Two new displacement potential functions are introduced for the general solution of a three-dimensional piezoelasticity problem for functionally graded transversely isotropic piezoelectric solids. The material properties vary continuously along the axis of symmetry of the medium. The four coupled equilibrium equations in terms of displacements and electric potential are reduced to two decoupled sixth- and second-order linear partial differential equations for the potential functions. The obtained results are verified with two limiting cases: (i) a functionally graded transversely isotropic medium, and (ii) a homogeneous transversely isotropic piezoelectric solid. The simplified relations... 

    Scattering of transverse surface waves by a piezoelectric fiber in a piezoelectric half-space with exponentially varying electromechanical properties

    , Article Zeitschrift fur Angewandte Mathematik und Physik ; Volume 70, Issue 2 , 2019 ; 00442275 (ISSN) Ghafarollahi, A ; Shodja, H. M ; Sharif University of Technology
    Birkhauser Verlag AG  2019
    Abstract
    In the present work, an analytical solution is presented for the scattering of transverse surface waves by a homogeneous piezoelectric fiber contained in a functionally graded piezoelectric half-space with exponential variation. The boundary value problem of interest is solved by constructing an appropriate set of multipole functions which satisfy: (a) the electromechanical field equations in the half-space, (b) the boundary conditions along its free surface, and (c) the far-filed radiation conditions. It is shown that the simple poles of these functions are related to the roots of the pertinent dispersion relation. For the case of electrically short condition along the free surface of the... 

    Development, modeling and deflection analysis of hybrid micro actuator with integrated thermal and piezoelectric actuation

    , Article Meccanica ; Volume 48, Issue 5 , 2013 , Pages 1081-1091 ; 00256455 (ISSN) Pourrostami, H ; Zohoor, H ; Kargarnovin, M. H ; Sharif University of Technology
    2013
    Abstract
    Micro actuators are irreplaceable part of motion control in minimized systems. The current study presents an analytical model for a new Hybrid Thermo Piezoelectric micro actuator based on the combination of piezoelectric and thermal actuation mechanisms. The micro actuator structure is a double PZT cantilever beam consisting of two arms with different lengths. The presented micro actuator uses the structure of electrothermal micro actuator in which polysilicon material is replaced by PZT. Also the voltage and poling directions are considered in the lengthwise of PZT beams. As a result, the piezoelectric actuation mechanism is based on d33 strain coefficient. The tip deflection of micro... 

    Dynamic and vibration analysis of a 3-serial-link micro/nano-manipulator with piezoelectric actuation

    , Article Microsystem Technologies ; Volume 27 , July , 2020 , Pages 703–721 Jafarishad, H ; Ahmadian, M. T ; Sharif University of Technology
    Springer  2020
    Abstract
    In this work, the dynamic and vibrational behavior of a micro/nano-manipulator has been studied. The manipulator comprises three links attached serially. While the connection of the links is rigid, which makes the whole body a monolithic structure, the movement of the manipulator is derived from the links deflection. Piezoelectric layers were employed as an actuator to impose deflection on the links, thereby moving the manipulator. After defining the dynamic behavior of each link, manipulator equations of motion were developed. To evaluate the validity of the mathematical model, two FEM models were constructed. The observed results showed a good agreement between the models, and they... 

    Dynamic and vibration analysis of a 3-serial-link micro/nano-manipulator with piezoelectric actuation

    , Article Microsystem Technologies ; Volume 27, Issue 3 , 2021 , Pages 703-721 ; 09467076 (ISSN) Jafarishad, H ; Ahmadian, M. T ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    In this work, the dynamic and vibrational behavior of a micro/nano-manipulator has been studied. The manipulator comprises three links attached serially. While the connection of the links is rigid, which makes the whole body a monolithic structure, the movement of the manipulator is derived from the links deflection. Piezoelectric layers were employed as an actuator to impose deflection on the links, thereby moving the manipulator. After defining the dynamic behavior of each link, manipulator equations of motion were developed. To evaluate the validity of the mathematical model, two FEM models were constructed. The observed results showed a good agreement between the models, and they... 

    Tip tracking control of a micro-cantilever Timoshenko beam via piezoelectric actuator

    , Article JVC/Journal of Vibration and Control ; Volume 19, Issue 10 , 2013 , Pages 1561-1574 ; 10775463 (ISSN) Shirazi, M. J ; Salarieh, H ; Alasty, A ; Shabani, R ; Sharif University of Technology
    2013
    Abstract
    In this paper, the tip tracking control problem of a Timoshenko micro-cantilever beam is investigated. The beam is actuated by a piezoelectric layer laminated on one side of the beam. Dynamic equations of the beam and piezoelectric layer are found using the Hamilton principle. By employing the Galerkin projection method, state space representation of the system is derived. Then, a cascade control loop is used for tracking control of the beam's tip. The cascade control structure consists of an inner loop stabilizer and an outer loop proportional-integral-derivative controller. The stabilizer has a linear feedback form whose states are obtained through a linear observer which is based on the... 

    The scattering of P-waves by a piezoelectric particle with FGPM interfacial layers in a polymer matrix

    , Article International Journal of Solids and Structures ; Volume 47, Issue 18-19 , 2010 , Pages 2390-2397 ; 00207683 (ISSN) Kamali, M. T ; Shodja, H. M ; Sharif University of Technology
    2010
    Abstract
    Propagation of P-wave in an unbounded elastic polymer medium which contains a set of nested concentric spherical piezoelectric inhomogeneities is formulated. The polymer matrix is made of Epoxy and is isotropic; each phase of the inhomogeneity is made of a different piezoelectric material and is radially polarized and has spherical isotropy. Note that the individual phases are homogeneous, and all interfaces are perfectly bonded. The scattered displacement and electric potentials in the matrix are expressed in terms of spherical wave vector functions and Legendre functions, respectively. The transmitted displacement and electric potentials within each phase of the piezoelectric particle are... 

    Design and analysis of a 3-link micro-manipulator actuated by piezoelectric layers

    , Article Mechanism and Machine Theory ; Volume 112 , 2017 , Pages 43-60 ; 0094114X (ISSN) Ahmadian, M. T ; Jafarishad, H ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    The purpose of this paper is to design and analyze a 3-link micro-device proposed as a micro-manipulator. This micro-manipulator includes 3 micro-beams as links connected to one another with no conventional or flexural joints. While the structure of the micro-manipulator is monolithic, end-effector workspace is achieved through deflection of links which is actuated by piezoelectric layers. By combining static analysis of the links through a multilayer piezoelectric beam model and kinematic analysis of the micro-manipulator, inverse kinematic has been solved utilizing the Taylor series expansion technique and the perturbation method. The obtained results through the present model reveal that... 

    Design and analysis of an elliptical-shaped linear ultrasonic motor

    , Article Sensors and Actuators, A: Physical ; Volume 278 , 2018 , Pages 67-77 ; 09244247 (ISSN) Sanikhani, H ; Akbari, J ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    A linear ultrasonic motor (LUSM) with an elliptical-shaped metallic stator and two orthogonal vibration modes is presented in this research. The driving tip's desired vibration is generated by the excitation of two piezoelectric actuators installed inside the stator by two sinusoidal voltages with ±[Formula presented] phase difference. The working principle of the motor is described and mathematically formulated. Furthermore, finite element analysis and parametric optimization are performed to finalize the motor design. A prototype of the motor is fabricated and evaluated by identification and operation tests. The experimental and numerical characteristic curves of the motor are presented... 

    Mechanical and piezoelectric characterizations of electrospun PVDF-nanosilica fibrous scaffolds for biomedical applications

    , Article 2017 INN International Conference/Workshop on Nanotechnology and Nanomedicine, NTNM 2017, 2 May 2017 through 3 May 2017 ; Volume 5, Issue 7 , 2018 , Pages 15710-15716 ; 22147853 (ISSN) Haddadi, S. A ; Ghaderi, S ; Amini, M ; Ramazani, S. A. A ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    The effects of hydrophilic and hydrophobic nanosilica (SiO2) on the morphology, mean diameter distribution of fibers, mechanical and piezoelectric properties of poly (vinylidene fluoride) (PVDF) nanofibers were studies. We prepared Nanofibers by the electrospinning of PVDF solutions containing 1.5 wt.% both hydrophilic and hydrophobic nano-SiO2 loadings. Morphology and diameter distribution of the electrospun nanofibers were studied using field emission scanning electron microscopy (FE-SEM) analysis. Tensile test was used to study the effect of both types of nanosilica on the tensile strength, young's modulus and strain at break. Piezoelectric characterization of the electrospun fibers were... 

    Application of active piezoelectric patches in controlling the dynamic response of a thin rectangular plate under a moving mass

    , Article International Journal of Solids and Structures ; Volume 46, Issue 11-12 , 2009 , Pages 2429-2443 ; 00207683 (ISSN) Rahimzadeh Rofooei, F ; Nikkhoo, A ; Sharif University of Technology
    2009
    Abstract
    The governing differential equation of motion for an undamped thin rectangular plate with a number of bonded piezoelectric patches on its surface and arbitrary boundary conditions is derived using Hamilton's principle. A moving mass traveling on an arbitrary trajectory acts as an external excitation for the system. The effect of the moving mass inertia is considered using all the out-of-plane translational acceleration components. The method of eigenfunction expansion is used to transform the equation of motion into a number of coupled ordinary differential equations. A classical closed-loop optimal control algorithm is employed to suppress the dynamic response of the system, determining the...