Papers by Alireza Shooshtari
Adaptive tracking control of a new nonlinear energy harvester system based on the cantilever beam structure
Journal of Vibration and Control, May 12, 2023
In this paper, an energy harvester consisting of a cantilever beam, magnets, and magnetic springs... more In this paper, an energy harvester consisting of a cantilever beam, magnets, and magnetic springs embedded on its structure is proposed to harvest electricity energy. In order to extract energy from the system permanently, an adaptive controller is proposed. With the help of the proposed controller, it is prevented from damping the oscillations of the beam or excessive increasing in the amplitude of these oscillations. Also, the use of the proposed controller provides the possibility that despite the presence of unknown external disturbances such as wind waves and sudden changes of sea waves, as well as the uncertainty of the parameters of the cantilever beam, a permanent energy is harvested from the proposed mechanism. The equations describing the electromechanical behavior of the proposed mechanism are derived from Lagrange equations. On the other hand, dynamic surface control technique is employed to design the adaptive and control laws. The stability of the closed-loop system is shown using Lyapunov stability theory, and the tracking error converges to a small neighborhood around the origin. Numerical simulation for cantilever beam is investigated to clarify the effectiveness of the proposed mechanism and controller.
Numerical investigation on the effects of crooked shaft washer of single row thrust ball bearing on its vibrational response
Journal of Vibration and Control, Jan 3, 2023
One of the most important types of misalignments is crooked ball bearing rings. In this study, ef... more One of the most important types of misalignments is crooked ball bearing rings. In this study, effects of crooked shaft washer related to a single-row thrust ball bearing on the system vibrating response have been investigated. For this purpose, a new dynamic model including 4-dof is considered for this bearing, housing and shaft mounted on it. Contact forces between rings and balls are described according to Hertzian equation. In the following, nonlinear Euler’s equilibrium is used to describe dynamic motion of the rings solved by numerical method. It is shown that these responses contain frequencies and phases that support the specialized signature of crookedness of the shaft washer in thrust ball bearing. Verification of responses has been done by Ansys software. The effect of amount of crookedness in the shaft washer and external axial force on the responses have also been investigated.
Journal of Computational & Applied Research in Mechanical Engineering (JCARME), Sep 11, 2014
In this paper, nonlinear equations of motion for laminated composite rectangular plates based on ... more In this paper, nonlinear equations of motion for laminated composite rectangular plates based on the first order shear deformation theory were derived. Using a perturbation method, the nonlinear equation of motion was solved and analytical relations were obtained for natural and nonlinear frequencies. After proving the validity of the obtained analytical relations, as an alternative and simple modeling technique, ANN was also employed to model the laminated rectangular plates and predict effects of different parameters on the natural and nonlinear frequencies of the plates. In this respect, an optimal ANN was selected and trained by training data sets obtained from analytical method and also tested by testing data sets. The obtained results were in good agreement with the analytical and published results.
Bearing Failure Analysis Using Vibration Analysis and Natural Frequency Excitation
Journal of Failure Analysis and Prevention
Mechanical behavior of a rectangular capacitive micro-plate subjected to an electrostatic load
International Journal of Dynamics and Control, 2022
This study aims at understanding the mechanical behavior and static response of an electrically a... more This study aims at understanding the mechanical behavior and static response of an electrically actuated micro-plate, considering the effects of different boundary conditions. The equations of motion of rectangular micro-plate-based micro- electro-mechanical systems are derived in terms of partial differential equations, exploiting the classical plate theory and von Kármán geometric nonlinearity. Two different boundary conditions are considered, i.e., simply supported and clamped with different in-plane conditions. The Galerkin procedure is employed to obtain a second-order nonlinear ordinary differential equation in time with quadratic, cubic, quartic, and higher nonlinear terms. The attention is mainly focused on the method of elimination of singularity in the electrostatic force. Therefore, two methods are implemented to treat singularity. By using the method of multiple time scales, the transient behavior of the system is obtained. Moreover, a discussion is made on how different design parameters affect the static response of micro-plates. In order to validate the obtained results, a numerical method by using Matlab®/Simulink® is employed.
Complete and partial vibration mode decoupling of national engine about torque roll axis
The Journal of Engine Research, 2015
Optimizing the Shape of Rubber Part of EF7 Engine Mount to Improve its Vibration Behavior
The Journal of Engine Research, 2017
Vibration of FGM Plates with Distributed Mass Using Third Order Shear Deformation Theory
Analytical Modeling for Energy Harvesting of Lateral Vibrations of Rotating Machines Via Electromagnetic Mechanisms
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering
In this paper, nonlinear free vibration of magneto-electro-elastic rectangular thin plate is inve... more In this paper, nonlinear free vibration of magneto-electro-elastic rectangular thin plate is investigated. The plate is supported by a nonlinear foundation and simply-supported boundary condition is assumed along all edges. The plate is considered in two forms; uniformly distributed one-layered plate and the functionally graded one. The plate is subjected to electric and magnetic potentials between top and bottom surfaces. Equations of motion of this smart plate are obtained by using classical plate theory along with the Gauss laws for electrostatics and magnetostatics. Then, the obtained equation of motion is analytically solved by using multiple time scales method. Effects of several parameters like plate's dimension, foundation parameter and electric and magnetic potentials on the nonlinear response of the plate are studied.
Nonlinear Vibration of an Electrostatically Excited Capacitive Microplate
Vibration Engineering for a Sustainable Future
Scientia Iranica, 2015
Nonlinear free vibration of symmetric circular fiber metal laminated (FML) hybrid plates is inves... more Nonlinear free vibration of symmetric circular fiber metal laminated (FML) hybrid plates is investigated. Considering the Von Karman geometric nonlinearity, the first order shear deformation theory (FSDT) is used to obtain the equations of motion. For the first time, five equations of motion of circular FML plates are derived in terms of plate displacements. The obtained equations are simplified for analyzing the first mode of symmetric circular plates. Using Galerkin method, five coupled nonlinear partial differential equations (PDEs) of motion are transformed to a single nonlinear ordinary differential equation (ODE) which is solved analytically by multiple time scales method, and an analytical relation is found for the nonlinear frequency of these plates. The obtained results are compared with the published results and good agreements are found. Moreover, the effects of several parameters on linear and nonlinear frequencies and the free vibration response are investigated.
Effect of Impeller Diameter on Dynamic Response of a Centrifugal Pump Rotor
This paper investigates the effect of impeller diameter on the dynamic response of a centrifugal ... more This paper investigates the effect of impeller diameter on the dynamic response of a centrifugal pump using an inverse dynamic method. For this purpose, the equations of motion of the shaft and the impeller are derived based on Timoshenko beam theory considering the impeller as a concentrated mass disk. For practical modeling, the model of Jones and Harris is added to the equation to include the effect of bearings. As a case study, the model is applied to a process pump used in an oil refinery. Computing the eigenvalues of the model and comparing them with the natural frequencies of the structure, the model updating of the problem is performed through an indirect method. Three impellers with different diameters are applied to the updated model. The results show that increasing the diameter of the pump impeller can increase the amplitude of vibration up to 52% at critical speeds of the rotor. It is found that in addition to the hydraulic condition and efficiency, the impeller diamete...
In this paper, the vibration characteristics of GFRP-stiffened pipes, in intact and cracked condi... more In this paper, the vibration characteristics of GFRP-stiffened pipes, in intact and cracked conditions are investigated. The results have different applications, which the most important ones are optimized designs of such pipes and diagnosis of the damage in them. Therefore, by Love theory, governing equations of motion for the GFRP-stiffened pipes were obtained. Having obtained characteristic equation, the natural frequencies of the problem were calculated for intact case. Then by modeling a sample of these pipes in the ANSYS software and using Modal analysis, natural frequencies and related mode shapes due to finite element method were calculated in cracked and intact conditions. Then by using the experimental modal analysis method, the natural frequencies of a sample, which was built similar to these pipes, were obtained in cracked and intact conditions. The results of the analytical method, finite element method, and the experimental modal analysis were compared and it was shown...
Residual stresses are one of the most important factors in the integrity of welded structures. Th... more Residual stresses are one of the most important factors in the integrity of welded structures. There have been vast majorities of research conducted on the mechanism of vibratory stress relief method (VSR), but the lack of a specific mechanism, explaining the process, was tangible. Therefore, in this article, the mechanism of VSR was explained using a new finite element model by focusing on the welded residual stresses, being widely used in industry. To be more specific, the effect of resonant vibration on residually stressed specimens was investigated numerically and experimentally. To model the welding simulation, a volumetric moving heat flux was defined using Goldak’s model in Abaqus/CAE. In addition, experiments were planned in a way to investigate not only the effects of vibration time, but also the effect of amplitude of the vibration. Residual stresses were measured using Incremental Centre Hole Drilling (ICHD) method. Finally, a mechanical shaker was designed and assembled ...
Gear Pump Root Cause Failure Analysis Using Vibrations Analysis and Signal Processing
Journal of Failure Analysis and Prevention
In this paper, gear pump failure because of bush bearing looseness is investigated. Vibrations an... more In this paper, gear pump failure because of bush bearing looseness is investigated. Vibrations analysis is one of the main manners of the diagnosis of mechanical failure. After bearing looseness, gears clearance is changed because of change between gears’ clearances. Time signal, spectrum velocity, spectrum accelerations, envelope velocity, and envelope accelerations are methods of vibrations analysis and signal processing to diagnose a failure in rotary machines. In this study, bush bearing failure and adhesive wear in gear using signal processing including machine spectrum, envelope spectrum acceleration, and acceleration spectrum are detected. Gear failure because of bush looseness has many symptoms that these symptoms are pronounced in this research. The best time for failure detection is the beginning of failure so the beginning of bush and worn gear’s teeth failure was found in this paper.
Scientia Iranica
In this study, the dynamical instabilities of a smart embedded micro-shell conveying pulsating ui... more In this study, the dynamical instabilities of a smart embedded micro-shell conveying pulsating uid ow are investigated based on nonlocal piezoelasticity theory and nonlinear cylindrical shell model. The micro-shell is surrounded by an elastic foundation, which is suitable for both Winkler spring and Pasternak shear modules. The internal uid ow is considered to be purely harmonic, irrotational, isentropic, Newtonian, and incompressible and is mathematically modeled using linear potential ow theory, time mean Navier Stokes equations, and Knudsen number. To bring the micro-scale problem closer to the reality, the pulsating viscous e ects and the slip boundary condition are also taken into account. Employing the modi ed Lagrange equations of motion for open systems, the nonlinear coupled governing equations are achieved and, consequently, the instability boundaries are obtained using Bolotin's method. In the section of numerical results, a comprehensive discussion about the dynamical instabilities of the system is presented (such as divergence, utter, and parametric resonance). It was found that the application of the positive electric potential eld would improve the stability of the system as an actuator or as a vibration amplitude controller in the micro electromechanical systems.
Scientia Iranica, Dec 29, 2018
In this study, the dynamical instabilities of an embedded smart micro-shell conveying pulsating f... more In this study, the dynamical instabilities of an embedded smart micro-shell conveying pulsating fluid flow is investigated based on nonlocal piezoelasticity theory and nonlinear cylindrical shell model. The micro-shell is surrounded by an elastic foundation which is suitable for both Winkler spring and Pasternak shear modules. The internal fluid flow is considered to be purely harmonic, irrotational, isentropic, Newtonian and incompressible and it is mathematically modeled using linear potential flow theory, time mean Navier Stokes equations and Knudsen number. For more reality of the micro-scale problem the pulsating viscous effects as well as the slip boundary condition are also taken into accounts. Employing the modified Lagrange equations of motion for open systems, the nonlinear coupled governing equations are achieved and consequently the instability boundaries are obtained using the Bolotin's method. In the numerical results section, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence; flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or as a vibration amplitude controller in the micro electro mechanical systems.
Suspension damping optimization using genetic algorithms
International Journal of Automotive Engineering and Technologies
Vehicle ride comfort is a function of the frequency of transmitting vibrations to passengers from... more Vehicle ride comfort is a function of the frequency of transmitting vibrations to passengers from road irregularities. The objective of this research is to provide a systematic method into the requirement of the passive suspension based on genetic algorithm (GA). Objective function of GA method is driver’s seat acceleration to provide driver ride comfort. The passive suspension damping coefficient and driver’s seat suspension damping coefficient have been optimized. In this paper, a vehicle with eight degrees of freedom has been simulated to achieve driver’s seat comfort. Analytical results explained by mathematical equations presented in the graphical form have been included.
Analytical solution and energy harvesting from nonlinear vibration of an asymmetric bimorph piezoelectric plate and optimizing the plate parameters by genetic algorithm
Journal of Intelligent Material Systems and Structures
In this article, harvesting of electrical power from nonlinear vibration of an asymmetric bimorph... more In this article, harvesting of electrical power from nonlinear vibration of an asymmetric bimorph piezoelectric plate is presented based on the classical plate theory with von Kármán strain–displacement nonlinear relations in the presence of temperature change effect. Two piezoelectric layers with different thicknesses cover top and bottom layers of a substructure. The structure has been excited under harmonic transverse forces in case of primary resonance. Two coupled ordinary differential equations for displacement and voltage have been derived and solved via multiple time scales method. The voltage equation has been defined by electric displacement and Gauss’s law. Analytic relations for voltage and harvested electrical power have been derived. The analytic relation for power is based on different parameters of the plate such as thicknesses of the layers, dimensions of plate, load resistance, frequency of harmonic excitation, and mechanical properties of structure. The parameters...
Uploads
Papers by Alireza Shooshtari