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Analysis of large amplitude free vibrations of clamped tapered beams on a nonlinear elastic foundation
, Article Applied Mathematical Modelling ; Volume 38, Issue 3 , 1 February , 2014 , Pages 1176-1186 ; ISSN: 0307904X ; Mazaheri, H ; Salarieh, H ; Sharif University of Technology
Abstract
The purpose of this paper is to present efficient and accurate analytical expressions for large amplitude free vibration analysis of single and double tapered beams on elastic foundation. Geometric nonlinearity is considered using the condition of inextensibility of neutral axis. Moreover, the elastic foundation consists of a linear and cubic nonlinear parts together with a shearing layer. The nonlinear governing equation is solved by employing the variational iteration method (VIM). This study shows that the second-order approximation of the VIM leads to highly accurate solutions which are valid for a wide range of vibration amplitudes. The effects of different parameters on the nonlinear...
Nonlinear membrane model for large amplitude vibration of single layer graphene sheets
, Article Nanotechnology ; Volume 22, Issue 30 , June , 2011 ; 09574484 (ISSN) ; Niaki, S. A ; Naghdabadi, R ; Asghari, M ; Sharif University of Technology
2011
Abstract
The nonlinear vibrational properties of single layer graphene sheets (SLGSs) are investigated using a membrane model. The nonlinear equation of motion is considered for the SLGSs by including the effects of stretching due to large amplitudes. The equation of motion is numerically solved utilizing the finite difference method for SLGSs with different initial and boundary conditions, sizes and pretensions. It is concluded that the nonlinear fundamental frequency of SLGSs increases by increasing the pretension and initial velocity. In addition, it is observed that an increase in the pretension weakens the effects of the initial velocity on the fundamental frequency, such that the fundamental...
Large amplitudes free vibrations and post-buckling analysis of unsymmetrically laminated composite beams on nonlinear elastic foundation
, Article Applied Mathematical Modelling ; Volume 35, Issue 1 , 2011 , Pages 130-138 ; 0307904X (ISSN) ; Jafari Talookolaei, R. A ; Salarieh, H ; Sharif University of Technology
Abstract
The purpose of this paper is to present efficient and accurate analytical expressions for large amplitude free vibration and post-buckling analysis of unsymmetrically laminated composite beams on elastic foundation. Geometric nonlinearity is considered using Von Karman's strain-displacement relations. Besides, the elastic foundation has cubic nonlinearity with shearing layer. The nonlinear governing equation is solved by employing the variational iteration method (VIM). This study shows that the third-order approximation of the VIM leads to highly accurate solutions which are valid for a wide range of vibration amplitudes. The effects of different parameters on the ratio of nonlinear to...
Finite time-Lyapunov based approach for robust adaptive control of wind-induced oscillations in power transmission lines
, Article Journal of Sound and Vibration ; Volume 371 , 2016 , Pages 19-34 ; 0022460X (ISSN) ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Academic Press
2016
Abstract
Large amplitude oscillation of the power transmission lines, which is also known as galloping phenomenon, has hazardous consequences such as short circuiting and failure of transmission line. In this article, to suppress the undesirable vibrations of the transmission lines, first the governing equations of transmission line are derived via mode summation technique. Then, due to the occurrence of large amplitude vibrations, nonlinear quadratic and cubic terms are included in the derived linear equations. To suppress the vibrations, arbitrary number of the piezoelectric actuators is assumed to exert the actuation forces. Afterwards, a Lyapunov based approach is proposed for the robust adaptive...
Analytical solution for large amplitude vibrations of microbeams actuated by an electro-static force
, Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1499-1507 ; 10263098 (ISSN) ; Asgarshamsi, A ; Goharkhah, M ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
An analytical study using Variational Iteration Method (VIM) is carried out in order to investigate the vibrations of electro-statically actuated double-clamped and simply-supported microbeams. Effects of applied voltage and residual axial load on the nonlinear natural frequency and deflection of the microbeams are studied. It shows that pre-compression in microbeams increases the amplitude of deflections for a specific applied voltage. Also, an increase in pre-tension motivates the microbeam to show more nonlinear behavior in an applied voltage. Predicted results are compared with the experimental data available in the literature and also with numerical results which shows a good agreement....
Nonlinear oscillation analysis of a pendulum wrapping on a cylinder
, Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 335-340 ; 10263098 (ISSN) ; Hosseinzadeh, A ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
In this paper, the nonlinear oscillation of a pendulum wrapping and unwrapping on two cylindrical bases is studied, and an analytical solution is obtained using the multiple scales method. The equation of motion is derived based on an energy conservation technique. By applying the perturbation method to the differential equation, the nonlinear natural frequency of the system is calculated, along with its time response. Analytical results are compared with numerical findings and good agreement is found. The effect of large amplitude and radius of cylinders on system frequency is evaluated. The results indicate that as the radius of the cylinder increases, the system frequency is increased....
Analytical approach to vibration analysis of a pendulum wrapping on a cylinder
, Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 7, Issue PARTS A AND B , November , 2011 , Pages 761-765 ; 9780791854938 (ISBN) ; Hosseinzadeh, A ; Ahmadian, M. T ; Barari, A ; Sharif University of Technology
Abstract
In this paper, nonlinear oscillation of a pendulum wrapping and unwrapping around two cylindrical bases is studied and an analytical solution is obtained using multiple scales method. Equations of motion are derived based on energy conservation technique. Applying perturbation method on the equations, nonlinear natural frequency of the system is calculated along with its time response. Analytical results are compared with numerical findings and good agreement is found. Effect of nonlinearity due to large amplitude and radius of cylinders on the system frequency is evaluated. Results indicate that as the radius of cylinder is increased, nonlinear frequency is enhanced. Initial amplitude plays...
Buzz cycle description in an axisymmetric mixed-compression air intake
, Article AIAA Journal ; Volume 54, Issue 3 , 2016 , Pages 1036-1049 ; 00011452 (ISSN) ; Sepahi Younsi, J ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2016
Abstract
Buzz phenomenon is shock oscillation ahead of the supersonic air intake when its mass flow rate is decreasing at offdesign condition. The buzz onset and the buzz cycle of an axisymmetric mixed-compression supersonic intake have been experimentally investigated through pressure recording and shadowgraph flow visualization. The intake was designed for a freestream Mach number of 2.0; however, tests were conducted for M∞ = 1.8, 2.0, and 2.2. All tests were performed at 0 deg angle of attack. Results show that there is a strong relation between the acoustic characteristics of the intake and the buzz fluctuations. This relation causes a new pattern for the buzz oscillations, large-amplitude...
On the energy extraction from large amplitude vibrations of MEMS-based piezoelectric harvesters
, Article Acta Mechanica ; Volume 228, Issue 10 , 2017 , Pages 3445-3468 ; 00015970 (ISSN) ; Ahmadian, M. T ; Zohoor, H ; Sharif University of Technology
Abstract
As sizes decrease, the advantages of application of piezoelectric materials for mechanical to electrical energy conversion become more obvious in comparison with electromagnetic and electrostatic techniques, according to uncomplicated fabrication processes of microscale piezoelectric harvesters together with their considerable amounts of generated power. Cantilevered silicon beams with surface bounded piezoelectric layers form the main structure of these MEMS-based harvesters. Lowering the resonance frequency down to the range of environmental vibration frequencies is one of the most significant challenges in MEMS harvesters which is usually attempted to be achieved by thinning the beam and...
Non-linear stress response of non-gap-spanning magnetic chains suspended in a newtonian fluid under oscillatory shear test: a direct numerical simulation
, Article Physics of Fluids ; Volume 29, Issue 10 , 2017 ; 10706631 (ISSN) ; Taghizadeh Manzari, M ; Fatehi, R ; Sharif University of Technology
Abstract
Adirect numerical simulation approach is used to investigate the effective non-linear viscoelastic stress response of non-gap-spanning magnetic chains suspended in a Newtonian fluid. The suspension is confined in a channel and the suspended clusters are formed under the influence of a constant external magnetic field. Large amplitude oscillatory shear (LAOS) tests are conducted to study the non-linear rheology of the system. The effect of inertia on the intensity of non-linearities is discussed for both magnetic and non-magnetic cases. By conducting magnetic sweep tests, the intensity and quality of the non-linear stress response are studied as a function of the strength of the external...
Derivation of the rovibrational Hamiltonian based on the tensor form: A new approach to generalized internal coordinates depending on the external parameters
, Article Molecular Physics ; Volume 106, Issue 19 , 2008 , Pages 2263-2269 ; 00268976 (ISSN) ; Tafazzoli, M ; Sharif University of Technology
2008
Abstract
The transformation of the complete (non-relativistic) molecular Hamiltonian from Cartesian to generalized coordinates based on the tensor form has been obtained. By taking generalized internal coordinates depending on two parameters we present an exact derivation of the molecular Hamiltonian that has simple and explicit expressions for general triatomic molecules, and all rovibrational couplings are determined. Our approach is applicable to various kinds of internal coordinates in a straightforward way. In this derivation, no approximations and no restrictions are imposed on the nature of the vibrational variables. We also introduce a straightforward method with minimum equations to obtain...
Nonlinear Analysis of MEMS-based Piezoelectric Vibrational Energy Harvesters
, Ph.D. Dissertation Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
Fabrication of various microelectromechanical sensors and actuators with low levels of energy consumption on one hand and the recent advances of microelectronic circuits technology leading to vast reduction in size and power consumption of CMOS circuitry on the other hand, have proposed the idea of developing MEMS-based environmental energy harvesting devices to provide their required power. These energy harvesters are an appropriate alternative for former heavy batteries of limited lifetime and can be utilized as a sustainable energy source for small intelligent systems. In the present research, the behavior of MEMS piezoelectric vibrational energy harvesters in nonlinear regime considering...
Analysis of large amplitude free vibrations of unsymmetrically laminated composite beams on a nonlinear elastic foundation
, Article Acta Mechanica ; Volume 219, Issue 1-2 , January , 2011 , Pages 65-75 ; 00015970 (ISSN) ; Salarieh, H ; Kargarnovin, M. H ; Sharif University of Technology
2011
Abstract
The large amplitude free vibration of an unsymmetrically laminated composite beam (LCB) on a nonlinear elastic foundation subjected to axial load has been studied. The equation of motion for the axial and transverse deformations of a geometrically nonlinear LCB is derived. Using the Ritz method, the governing equation is reduced to a time-dependent Duffing equation with quadratic and cubic nonlinearities. The homotopy analysis method (HAM) is used to obtain exact expressions for the dynamic response of the LCB. This study shows that the third-order approximation of the HAM leads to highly accurate solutions that are valid for a wide range of vibration amplitudes. The effects of different...
Large amplitude thermo-mechanical vibration analysis of asymmetrically laminated composite beams
, Article Key Engineering Materials, 22 March 2011 through 24 March 2011, Kuala Lumpur ; Volume 471-472 , 2011 , Pages 745-750 ; 10139826 (ISSN) ; 9783037850596 (ISBN) ; Alavijeh, H. S ; Pasharavesh, A ; Aghdam, M. M ; Sharif University of Technology
2011
Abstract
In this paper, simple analytical expression is presented for large amplitude thermomechanical free vibration analysis of asymmetrically laminated composite beams. Euler-Bernoulli assumptions together with Von Karman's strain-displacement relation are employed to derive the nonlinear governing partial differential equation (PDE) of motion. He's variational method is employed to obtain a simple and efficient approximate closed form solution of the nonlinear governing equation. Comparison between results of the present work and those available in literature shows the accuracy of presented technique. Some new results for the nonlinear natural frequencies of the laminated beams such as the effect...
Classification of the nonlinear dynamics in an initially curved bistable micro/nanoelectro-mechanical system resonator
, Article Micro and Nano Letters ; Volume 10, Issue 10 , Oct , 2015 , Pages 583-588 ; 17500443 (ISSN) ; Hairi Yazdi, M. R ; Nejat Pishkenari, H ; Maani Miandoab, E ; Ouakad, H.M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
The nonlinear dynamics of a bistable micro/nano-electro-mechanical system resonator composed of an arch-shaped microbeam is investigated. The initially curved microbeam is actuated through a combined DC and AC electrostatic parallel plate field. A single degree of freedom model obtained using the Galerkin's decomposition method with distributed electrostatic force is implemented in order to investigate the resonator dynamics near its primary resonance. According to the shape of the potential energy function which depends on the system parameters, the nonlinear dynamics of the system are classified into certain categories. The appearance of various nonlinear phenomena including dynamic...
Nonlinear vibration of a three-dimensional moving gantry crane subjected to a travelling trolley hoisting a swinging object
, Article Transactions of the Canadian Society for Mechanical Engineering ; Volume 34, Issue 3-4 , 2010 , Pages 333-350 ; 03158977 (ISSN) ; Ghafoori, E ; Sadeghpour, M ; Sharif University of Technology
2010
Abstract
Nonlinear vibration of a three-dimensional moving gantry crane carrying a trolley hoisting a swinging object is studied in this paper.A finite element method is used to solve nonlinear coupled governing equations of the structure. A combinational technique (Newmark-Runge-Kutta) is employed for direct integration procedure. To develop a comprehensive parametric study and sensitivity analysis of the coupled nonlinear system, sequence of numerical simulations are carried out. Parametric study is directed to find out how different parameters like speed and acceleration of the trolley and gantry crane as well as the mass of the moving trolley and swinging object may affect the linear and...
Design of pid controller for control of speed of the robotic fish modeled by Lighthill's large amplitude elongated body theory in linear path
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009, Lake Buena Vista, FL ; Volume 10, Issue PART A , 2010 , Pages 117-124 ; 9780791843833 (ISBN) ; Meghdari, A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2010
Abstract
Design of robotic fish based on hydrodynamics is presented and Lighthill's Large Amplitude Elongated Body Theory (LAEBT) is used for modeling of the robotic fish in linear path. A PID controller for control of speed in linear path is designed and simulations are presented which shows its effectiveness for speed control of the robotic fish. It has been shown that in perspective of used approximate LAEBT model, the used control law maintains kinematic parameters and therefore, the associated efficiency will be maintained
Electromechanical modeling and analytical investigation of nonlinearities in energy harvesting piezoelectric beams
, Article International Journal of Mechanics and Materials in Design ; 2016 , Pages 1-16 ; 15691713 (ISSN) ; Ahmadian, M. T ; Zohoor, H ; Sharif University of Technology
Springer Netherlands
2016
Abstract
Piezoelectric materials are extensively applied for vibrational energy harvesting especially in micro-scale devices where other energy conversion mechanisms such as electromagnetic and electrostatic methods encounter fabrication limitations. A cantilevered piezoelectric bimorph beam with an attached proof (tip) mass for the sake of resonance frequency reduction is the most common structure in vibrational harvesters. According to the amplitude and frequency of applied excitations and physical parameters of the harvester, the system may be pushed into a nonlinear regime which arises from material or geometric nonlinearities. In this study nonlinear dynamics of a piezoelectric bimorph harvester...
Nonlinear free vibration and post-buckling analysis of functionally graded beams on nonlinear elastic foundation
, Article European Journal of Mechanics, A/Solids ; Volume 30, Issue 4 , July , 2011 , Pages 571-583 ; 09977538 (ISSN) ; Aghdam, M. M ; Sharif University of Technology
2011
Abstract
In this study, simple analytical expressions are presented for large amplitude free vibration and post-buckling analysis of functionally graded beams rest on nonlinear elastic foundation subjected to axial force. Euler-Bernoulli assumptions together with Von Karman's strain-displacement relation are employed to derive the governing partial differential equation of motion. Furthermore, the elastic foundation contains shearing layer and cubic nonlinearity. He's variational method is employed to obtain the approximate closed form solution of the nonlinear governing equation. Comparison between results of the present work and those available in literature shows the accuracy of this method. Some...