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Experimental parametric identification of a flexible beam using piezoelectric sensors and actuators
, Article Shock and Vibration ; Vol. 2014, Issue. 1 , 2014 ; ISSN: 1070-9622 ; Nobahari, H ; Kordkheili, S. A. H ; Sharif University of Technology
2014
Abstract
Experimental system identification of a flexible beam based on sweep square excitation is studied. For the purpose of nonparametric identification, an excitation signal is conducted to evaluate the frequency response of the system. The experiment is designed to excite the beam using a piezo actuator, in a way to raise the chance of exciting first three natural modes. In order to find the best linear representation of the real system, two different identification methods are applied. First, autoregressive moving average eXogenous method is employed to identify the transfer function of the beam. Then, the identification is carried out using the subspace identification method to obtain the...
A lumped parameter model for exponentially tapered piezoelectric beam in transverse vibration
, Article Journal of Mechanical Science and Technology ; Volume 33, Issue 5 , 2019 , Pages 2043-2048 ; 1738494X (ISSN) ; Salmani, H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Korean Society of Mechanical Engineers
2019
Abstract
Tapered piezoelectric beams, because of their more efficiency to generate power, are required to be analyzed by simple models. In this paper, single degree of freedom (SDOF) relations are used to model transvers vibration of an exponentially tapered piezoelectric beam. For this purpose, first, response of the damped cantilevered Euler–Bernoulli beam with base excitation is obtained. Then, lumped parameters of the beam are extracted in order to calculate the SDOF model response. Comparing the Euler-Bernoulli beam model with the SDOF model shows that the lumped parameter model is not accurate enough to predict the beam’s response. Therefore, a tapering parameter dependent correction factor is...
Nonlinear dynamics of viscoelastic pipes conveying fluid placed within a uniform external cross flow
, Article Applied Ocean Research ; Volume 94 , 2020 ; Haddadpour, H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This paper investigates the nonlinear dynamic response of a viscoelastic pipe conveying fluid subjected to a uniform external cross flow based on the Euler-Bernoulli theory. The main objective of this work is to find the proper viscoelastic coefficients to mitigate the dynamic response of a marine riser. A nonlinear oscillator is utilized to simulate the mean drag force and the vortex-induced lift force. Also, the pipe material is assumed to be viscoelastic and consisted of the Kelvin-Voigt type. The extended Hamilton's principle along with the Galerkin discretization are employed to construct the nonlinear model of the coupled fluid-structure system. Moreover, the assumed mode method along...
Progressive bearing failure modeling of composites with double-bolted joints at mesoscale level
, Article Archive of Applied Mechanics ; Vol. 84, issue. 5 , May , 2014 , p. 657-669 ; 09391533 ; Hosseini Kordkheili, S. A ; Toozandehjani, H ; Sharif University of Technology
2014
Abstract
Both numerical and experimental researches are carried out to study the strength of the composite double-bolted joints and the bearing damage propagation. A mesoscale level progressive damage model along with analytical formulation is used to predict the bearing failure of carbon-epoxy composite plates. This damage model is introduced as a user material subroutine in the commercial software ABAQUS, and the maximum failure load is calculated. In order to validate the numerical results, experimental tests are also conducted in which comparison between the results shows an excellent agreement. Furthermore, the effects of the bolt distances on the maximum failure load are studied. The results...
An analytical and experimental study on dampening material effects on the dynamic behavior of free-free aluminum sheets
, Article Engineering Solid Mechanics ; Volume 9, Issue 2 , 2021 , Pages 111-122 ; 22918744 (ISSN) ; Hosseini Kordkheili, S. A ; Parviz, H ; Sharif University of Technology
Growing Science
2021
Abstract
This work aims to present an experimentally verified analytical solution to examine damping properties of systems including viscoelastic treatments. Although there are several methods for characterizing the behavior of three-layer damping systems, the RKU method is the most frequently used one. In this paper, this method is modified such a way that to be applied for a five-layer damping system. The achieved analytical relations are then employed to study the effects of a four-layer vibration-absorbing coating on the dynamic behavior of an aluminum sheet with free-free boundary conditions. Since the vibration-damping properties of the coating are unknowns, its loss factor and shear modulus...
Combining pole placement and online empirical mode decomposition methods to adaptive active control of structural vibration
, Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 141, Issue 4 , 2019 ; 10489002 (ISSN) ; Hosseini Kordkheili, S. A ; Navazi, H. M ; Bahai, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
Using a combination of the pole placement and online empirical mode decomposition (EMD) methods, a new algorithm is proposed for adaptive active control of structural vibration. The EMD method is a time-frequency domain analysis method that can be used for nonstationary and nonlinear problems. Combining the EMD method and Hilbert transform, which is called Hilbert-Huang transform, achieves a method that can be implemented to extract instantaneous properties of signals such as structural response dominant instantaneous frequencies. In the proposed algorithm, these estimated instantaneous properties are utilized to improve the pole-placement method as an adaptive active control technique. The...
An exact Analytical solution to exponentially tapered piezoelectric energy harvester
, Article Shock and Vibration ; Volume 2015 , 2015 ; 10709622 (ISSN) ; Rahimi, G. H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Hindawi Publishing Corporation
2015
Abstract
It has been proven that tapering the piezoelectric beam through its length optimizes the power extracted from vibration based energy harvesting. This phenomenon has been investigated by some researchers using semianalytical, finite element and experimental methods. In this paper, an exact analytical solution is presented to calculate the power generated from vibration of exponentially tapered unimorph and bimorph with series and parallel connections. The mass normalized mode shapes of the exponentially tapered piezoelectric beam with tip mass are implemented to transfer the proposed electromechanical coupled equations into modal coordinates. The steady states harmonic solution results are...
A particular criterion for progressive failure analysis of carbon/phenolic tape-wounded conic shells
, Article International Journal of Damage Mechanics ; Volume 30, Issue 8 , 2021 , Pages 1238-1260 ; 10567895 (ISSN) ; Karimian, M ; Jafari, H. R ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
Conic shell structures are widely used in aerospace industries. In the literature various models have been proposed to failure analysis of composite materials. Clearly, each model has a favorable range of applications. In this paper tensile, compressive, shear and thermal expansion properties of tape-wounded Carbon/Phenolic composites are firstly measured at various temperatures in range 23–200°C. The captured properties are then taken into account to progressive failure analysis of a conic Carbon/Phenolic structure under internal pressure and thermal loadings. For this end, a particular failure criterion is proposed to predict failure in the composite structures with a reasonable margin of...
A fast online bandwidth empirical mode decomposition scheme for avoidance of the mode mixing problem
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 20 , 2018 , Pages 3652-3674 ; 09544062 (ISSN) ; Hosseini Kordkheili, S. A ; Navazi, H. M ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
The main objective of this work is to propose a scheme to extract intrinsic mode functions of online data with an acceptable speed as well as accuracy. For this purpose, an individual block framework method is firstly employed to extract the intrinsic mode functions. In this method, buffers are selected such that they overlap with their neighbors to prevent the end effect errors with no need for the averaging process. And in order to avoid the mode mixing problem, a bandwidth empirical mode decomposition scheme is developed to effectively improve the results. Through this scheme, an auxiliary function made of both high- and low-frequency components corresponding to noise and dominant...
Bonded composite patch repair’s fiber VF effects on damaged Al-plates fatigue employing a multi-scale algorithm
, Article Journal of Reinforced Plastics and Composites ; Volume 40, Issue 1-2 , 2021 , Pages 29-40 ; 07316844 (ISSN) ; Barzegar, M ; Abedian, A ; Kordkheili, S. A. H ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
Recently, bonded composite patch repair, because of its significant advantages over traditional methods, has been highly accepted in several industries, particularly in aerospace applications. In this paper, a multi-scale finite element algorithm is proposed to simulate crack growth of repaired plates under fatigue load by considering the effects of composite micro-scale properties. The algorithm is verified through conducting an experimental set up and the proposed model is in reasonable agreement with experiments. The influences of different fiber volume fractions (VF), number of layers and fiber orientation of composite patch on the fatigue responses of adhesively bonded patch are...
On the multi-scale computation of un-bonded flexible risers
, Article Engineering Structures ; Volume 32, Issue 8 , August , 2010 , Pages 2287-2299 ; 01410296 (ISSN) ; Alfano, G ; Bahai, H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
2010
Abstract
The purpose of this paper is to model the detailed effects of interactions that take place between components of un-bonded flexible risers, and to study the three-dimensional motion responses of risers when subjected to axial loads, bending moments, and internal and external pressures. A constitutive law for un-bonded flexible risers is proposed and a procedure for the identification of the related input parameters is developed using a multi-scale approach. A generalized finite element structural model based on the Euler-Bernoulli beam theory is developed in which the constitutive law is embedded. The beam theory is enhanced by the addition of suitable pressure terms to the generalized...
Effective mechanical properties of unidirectional composites in the presence of imperfect interface
, Article Archive of Applied Mechanics ; Vol. 84, issue. 6 , June , 2014 , pp. 807-819 ; Print ISSN: 0939-1533 ; Toozandehjani, H ; Sharif University of Technology
2014
Abstract
In this paper, the equivalent inclusion method is implemented to estimate the effective mechanical properties of unidirectional composites in the presence of an imperfect interface. For this purpose, a representative volume element containing three constituents, a matrix, and interface layer, and a fiber component, is considered. A periodic eigenstrain defined in terms of Fourier series is then employed to homogenize non-dilute multi-phase composites. In order to take into account the interphase imperfection effects on mechanical properties of composites, a stiffness parameter in terms of a matrix and interphase elastic modulus is introduced. Consistency conditions are also modified...
Experimental identification of closely spaced modes using NExT-ERA
, Article Journal of Sound and Vibration ; Volume 412 , 2018 , Pages 116-129 ; 0022460X (ISSN) ; Momeni Massouleh, S. H ; Hajirezayi, S ; Bahai, H ; Sharif University of Technology
Academic Press
2018
Abstract
This article presents a study on the capability of the time domain OMA method, NExT-ERA, to identify closely spaced structural dynamic modes. A survey in the literature reveals that few experimental studies have been conducted on the effectiveness of the NExT-ERA methodology in case of closely spaced modes specifically. In this paper we present the formulation for NExT-ERA. This formulation is then implemented in an algorithm and a code, developed in house to identify the modal parameters of different systems using their generated time history data. Some numerical models are firstly investigated to validate the code. Two different case studies involving a plate with closely spaced modes and...
A stabilized piezolaminated nine-nodded shell element formulation for analyzing smart structures behaviors
, Article Mechanics of Advanced Materials and Structures ; Volume 23, Issue 2 , 2016 , Pages 187-194 ; 15376494 (ISSN) ; Salmani, H ; Afshari, S. S. G ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
An explicit hybrid stabilization method is utilized together with a reduced order integration scheme to stabilize spurious zero energy modes from the sub-integrated degenerated shell element. This stabilization is achieved after employing appropriate contravariant higher order stress modes. The relevant finite element formulation of the piezolaminated nine-nodded shell element is then derived to analyze smart structures behaviors. To show the capabilities of the presented formulation, it has been implemented in a finite element code. The developed code is used to analyze some typical problems. The results are compared with those obtained from other schemes in the literature and experiments
Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms
, Article Journal of Intelligent Material Systems and Structures ; Vol. 25, issue. 10 , 2014 , p. 1211-1223 ; Hosseini Kordkheili, S. A ; Afshari, S. S ; Sharif University of Technology
2014
Abstract
In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization...
Mechanical properties of double-layered graphene sheets
, Article Computational Materials Science ; Volume 69 , 2013 , Pages 335-343 ; 09270256 (ISSN) ; Moshrefzadeh Sani, H ; Sharif University of Technology
2013
Abstract
In this paper, the molecular structural mechanics method is employed to calculate the mechanical properties of a double-layered carbon graphene sheet more accurately. For this purpose, covalent bonds are modeled using nonlinear beam elements and van der Waals interactions are replaced by nonlinear truss elements. Morse potential and Lennard-Jones potential equations are used to simulate the covalent bonds and van der Waals interactions, respectively. For each atom, van der Waals forces are considered with respect to all the other atoms located in its cut-off radius. In addition to in-plane mechanical properties of single and double-layered graphene sheets some out-of-plane properties like...
A finite element formulation for analysis of functionally graded plates and shells
, Article Archive of Applied Mechanics ; Volume 74, Issue 5-6 , 2005 , Pages 375-386 ; 09391533 (ISSN) ; Hosseini Kordkheili, S. A ; Sharif University of Technology
2005
Abstract
A finite element formulation is derived for the thermoelastic analysis of functionally graded (FG) plates and shells. The power-law distribution model is assumed for the composition of the constituent materials in the thickness direction. The procedure adopted to derive the finite element formulation contains the analytical through-the-thickness integration inherently. Such formulation accounts for the large gradient of the material properties of FG plates and shells through the thickness without using the Gauss points in the thickness direction. The explicit through-the-thickness integration becomes possible due to the proper decomposition of the material properties into the product of a...
An investigation on dynamic behavior of rotating shafts using a pipe elbow finite element formulation
, Article Engineering Solid Mechanics ; Volume 10, Issue 2 , 2022 , Pages 179-190 ; 22918744 (ISSN) ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Growing Science
2022
Abstract
Rotating shafts have a vast application in various industries especially in the aerospace industry such as engines, compressors and turbines. The researchers have performed considerable efforts on the rotating shafts’ dynamic behavior because of their sensitivity to the rotor specifications and different parameters such as supports. In this paper by employing a pipe elbow element, an especial finite element formulation is derived to investigate dynamic behavior of rotating shaft in the presence of support clearance. The proposed element consists of four nodes with twenty-four degrees of freedom, which also accounts for the shear and gyroscopic effects. Within a finite element analysis...
Interlaminar stress analysis of composite shell structures using a geometrically nonlinear layer-wise shell finite element
, Article Composite Structures ; Volume 257 , 2021 ; 02638223 (ISSN) ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
This work aims to calculate interlaminar stress distribution through the thickness of multilayered composite shell structures by employing a novel nonlinear layer-wise shell finite element formulation. Adapting the Mindlin– Reissner theory in each layer, the shear-deformable layer-wise shell element presents the interlaminar shear stress distributions by increasing the number of layers. The interlaminar normal stress distribution is then determined using the finite difference solution of the general form of equilibrium equation in the non-orthogonal curvilinear grid along the Gaussian points. Two boundary conditions at the bottom and the top surfaces are satisfied by adopting the linear...
A continuum constitutive model for mechanical behavior of 5052 resin epoxy containing various percentages of MWCNTs
, Article Journal of Composite Materials ; Volume 51, Issue 17 , 2017 , Pages 2423-2434 ; 00219983 (ISSN) ; Toozandehjani, H ; Ashouri Choshali, H ; Boroumand Azad, S ; Sharif University of Technology
SAGE Publications Ltd
2017
Abstract
In this article, a continuum-based constitutive model is developed to predict the mechanical behavior of 5052 resin epoxy reinforced by multiwalled carbon nanotubes (MWCNTs) based on experimentally generated data. For this purpose, MWCNTs/epoxy specimens with various percentages of functionalized and nonfunctionalized MWCNTs are prepared. The SEM graphs indicate that functionalization leads to a better bound between epoxy and MWCNTs and a higher level of dispersion. The specimens are then tested under standard ASTM D638-02 a procedure and their true plastic stress–strain curves are extracted. Investigations on experimentally generated data reveal that a wt% dependent equation which is...