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viscoelasticity
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Chaotic analysis of nonlinear viscoelastic panel flutter in supersonic flow
, Article Nonlinear Dynamics ; Volume 32, Issue 4 , 2003 , Pages 387-404 ; 0924090X (ISSN) ; Fazelzadeh, S. A ; Sharif University of Technology
2003
Abstract
In this paper chaotic behavior of nonlinear viscoelastic panels in a supersonic flow is investigated. The governing equations, based on von Kàrmàn's large deflection theory of isotropic flat plates, are considered with viscoelastic structural damping of Kelvin's model included. Quasi-steady aerodynamic panel loadings are determined using piston theory. The effect of constant axial loading in the panel middle surface and static pressure differential have also been included in the governing equation. The panel nonlinear partial differential equation is transformed into a set of nonlinear ordinary differential equations through a Galerkin approach. The resulting system of equations is solved...
Stochastic analysis of nonlinear viscoelastic panels under random excitation
, Article 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Norfolk, VA, 7 April 2003 through 10 April 2003 ; Volume 6 , 2003 , Pages 4219-4225 ; 02734508 (ISSN) ; Pourtakdoust, S. H ; Assadian, N ; Sharif University of Technology
American Inst. Aeronautics and Astronautics Inc
2003
Abstract
Stochastic behavior of viscoelastic panels in supersonic flow under random aerodynamic pressure and in-plane forces is investigated. The governing equations of motion are based on the Von Karman's large deflection equation and are considered with Kelvin's model of viscoelastic structural damping. The panel under study is two dimensional and simply supported for which the first order piston theory is used to account for the unsteady aerodynamic loading. Transformation of the governing partial differential equation to a set of ordinary differential equations is performed through the Galerkin averaging technique. The statistical response moment equations are generated for two modes using the...
Analysis of Sandwich Beam Vibration Due to Moving Mass
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor) ; Asgari, Mojtaba (Co-Supervisor)
Abstract
In this research, mathematical modeling, deriving equations of motion, solving equations and analyzing the response of motion vibrations of a moving mass with constant speed on a sandwich beam have been discussed. The sandwich beam consists of three layers, the middle layer of which is made of viscoelastic material, and the upper and lower layers are the Euler-Bernoulli beam model.At first, this sandwich beam is mathematically modeled, This mathematical modeling includes all the specifications of the system to obtain the equations that govern the behavior of the system. Then, the displacement field of the system has been extracted and the equations of motion of the system have been obtained...
Modeling and Manipulation of Intracytoplasmic Cell Injection
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor)
Abstract
The injection process on cell is a very accurate and sensitive operation. This method is used for several new invented approaches such as tracytoplasmic Cell Injection or drug delivery. Controlling the injection force in micro scale is one of the problems of mentioned operations. Current huge and expensive laboratorial devices are helping the operators to do injection operation with :nore success. In this study a simple and novel microelectromechanical (MEMS) mechanism for doing injection process automatically on the biological cells is proposed. In order to controlling this device properly, we should model and simulate the operation condition from initial position to final condition. This...
Pore Scale Modeling of Fluid-Fluid Intercations During Low Salinity Waterflooding
, M.Sc. Thesis Sharif University of Technology ; Ayatollahi, Shahab (Supervisor) ; Mahani, Hassan (Supervisor)
Abstract
Recent studies have shown that the injection of low-salinity water would enhance the oil recovery factor for both the core scale and the field test. The evidence obtained from laboratory studies showed that the control of salinity and the composition of injected water has successfully affected the oil release, hence enhancing the oil recovery efficiency. In this method, by changing the type and amount of dissolved ions in the injected water, the water/oil/rock interactions are altered. Based on this, extensive studies have been focused on the mechanisms for the trapped oil release at the pore scale. Several mechanisms have been proposed to explain this phenomenon, which can be divided...
Recent studies have shown that the injection of low-salinity water would enhance the oil recovery factor for both the core scale and the field test. The evidence obtained from laboratory studies showed that the control of salinity and the composition of injected water has successfully affected the oil release, hence enhancing the oil recovery efficiency. In this method, by changing the type and amount of dissolved ions in the injected water, the water/oil/rock interactions are altered. Based on this, extensive studies have been focused on the mechanisms for the trapped oil release at the pore scale. Several mechanisms have been proposed to explain this phenomenon, which can be divided...
Non-Linear Aeroelastic Analysis of Three-Layered Plates with Magneto-Rheological Fluid Core in Supersonic Airflow
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
This study is a comprehensive analysis on the nonlinear vibration of a sandwich plate containing magnetorheological (MR) fluid as the core layer. The nonlinear aeroelastic analysis of the structure is also discussed to determine the flutter boundaries. In this study, the numerical Generalized Differential Quadrature (GDQ) method is applied to investigate the free vibration analysis of a sandwich plate with a MR fluid core. The classical thin plate theory (CPT) and the First-order Shear Deformation Theory (FSDT) are assumed for face layers and core layer, respectively. These theories along with Von-Karman kinematic formulations are incorporated to extract governing equations. The equations of...
Forced and free vibrational analysis of viscoelastic nanotubes conveying fluid subjected to moving load in hygro-thermo-magnetic environments with surface effects
, Article Archives of Civil and Mechanical Engineering ; Volume 22, Issue 4 , 2022 ; 16449665 (ISSN) ; Alibeigloo, A ; Borjalilou, V ; Koochakianfard, O ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Forced and free vibrational analyses of viscoelastic nanotubes containing fluid under a moving load in complex environments incorporating surface effects are conducted based on the nonlocal strain gradient theory and the Rayleigh beam model. To model the internal nanoflow, the slip boundary condition is employed. Adopting the Galerkin discretization approach, the reduced-order dynamic model of the system is acquired. Analytical and numerical methods are exploited to determine the dynamic response of the system. The impacts of geometry, scale parameter ratio, Knudsen number, fluid velocity, rotary inertia parameter, viscoelastic parameter, surface residual stress, surface elastic modulus, and...
An intelligent computer method for vibration responses of the spinning multi-layer symmetric nanosystem using multi-physics modeling
, Article Engineering with Computers ; Volume 38 , 2022 , Pages 4217-4238 ; 01770667 (ISSN) ; Baharvand, A ; Tazeddinova, D ; Habibi, M ; Safarpour, H ; Roco-Videla, A ; Selmi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
This article is the first attempt to employ deep learning to estimate the frequency performance of the rotating multi-layer nanodisks. The optimum values of the parameters involved in the mechanism of the fully connected neural network are determined through the momentum-based optimizer. The strength of the method applied in this survey comes from the high accuracy besides lower epochs needed to train the multi-layered network. It should be mentioned that the current nanostructure is modeled as a nanodisk on the viscoelastic substrate. Due to rotation, the centrifugal and Coriolis effects are considered. Hamilton’s principle and generalized differential quadrature method (GDQM) are presented...
Design and Manufacture of Polymeric Nanocomposite in Order to Control the Production and Migration of Sand in Reservoirs
, Ph.D. Dissertation Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor)
Abstract
Sand production from oil reservoirs leads to various problems, such as well productivity reduction, operating equipment corrosion, and increased production costs. Therefore, controlling sand production in unconsolidated reservoirs is crucial for operating companies. Chemical injection into the formation in order to strengthen and reduce sand production is one of the most important methods of sand control. In this study, a hydrogel nanocomposite was designed and its effectiveness in sand control was investigated. Various tests were carried out to define and assess its efficacy, as follows: Morphological tests demonstrated the creation of a dense, homogeneous, and porous structure. Structural...
Coupled bending torsional vibrations of viscoelastic rotors with fractional damper
, Article JVC/Journal of Vibration and Control ; 2022 ; 10775463 (ISSN) ; Haddadpour, H ; Zamani, Z ; Sharif University of Technology
SAGE Publications Inc
2022
Abstract
The behavior of a Jeffcott rotor with lateral-torsional coupling is investigated in the presence of internal and external damping and eccentricity. The governing equations are derived based on the Lagrange method. Also, the Laplace method and linearization is used to solve the governing equations for free vibrations analysis. For a rotor with unbalance, the instability occurs when the real part of eigenvalues has positive values, and at the same time, it is the intersection point between the lines of natural frequencies. The instability speed increases with increasing the external damping, yet dependent on the internal damping and unbalance. Also, it is demonstrated that the rotor critical...
Size effects on stability and bifurcation of nonlinear viscoelastic microcantilevers based on strain gradient
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 44, Issue 1 , 2022 ; 16785878 (ISSN) ; Ahmadian, M. T ; Monfared, V ; Toghraie, D ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Analytical frequency analysis of a nonlinear viscoelastic microcantilever is performed based on strain gradient theory. The Kelvin–Voigt scheme is utilized to model the viscoelasticity effect. Due to the microcantilever shortening effect via Euler–Bernoulli inextensibility condition, geometric, inertia, stiffness, and inherent damping nonlinearities are considered. The equation of motion is derived from Hamilton’s principle, and discretized using Galerkin method. The multiple timescale perturbation method is performed to solve the time response equation. Implying steady-state condition, the nonlinear relation between detuning parameter and amplitude of the vibration of a nonlinear...
Viscoelastic dynamics and static responses of a graphene nanoplatelets-reinforced composite cylindrical microshell
, Article Mechanics Based Design of Structures and Machines ; Volume 50, Issue 2 , 2022 , Pages 509-536 ; 15397734 (ISSN) ; Ghabussi, A ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this study, a cylindrical microshell stability reinforced by graphene nanoplatelets is investigated while an axial load is applied uniformly. In addition, viscoelastic foundation covers the composite nanostructure. Therefore, the impacts of the small scale parameter are studied while nonlocal strain gradient theory (NSGT) is considered. The present research deals for the first time with the consideration of viscoelastic, strain–stress size-dependent parameters along with taking into account of various boundary conditions (BCs), especially C-F ones put into effect on the proposed theory. The governing equations (G.Eqs) and BCs have been obtained utilizing energy method and solved with...
Characterization of nanoscale structural heterogeneity in metallic glasses: A machine learning study
, Article Journal of Non-Crystalline Solids ; Volume 578 , 2022 ; 00223093 (ISSN) ; Gholamipour, R ; Bokov, D.O ; Suksatan, W ; Samavatian, V ; Mahmoodan, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Atomic force microscopy (AFM) is an efficient tool for studying the structural heterogeneity in metallic glasses (MGs). However, time-consuming analysis and limitations in the scanning process are downsides of this experiment. To tackle these problems, a machine learning (ML) model was developed to predict the distribution of energy dissipation on the MG surface with the increase in number of AFM scanning. The results indicated that it was possible to accurately predict the energy of scanning points, leading to a timesaving and reliable study. Moreover, characterization of structural heterogeneity shows that the viscoelastic response of each nanoscale region under sequences of AFM scans...
Structural Dynamic Instability of Flutter in Flapping Wing MAV by Develop A Nonlinear Finite Element Method
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkheili, Ali (Supervisor) ; Malaek, Mohamad Bagher (Supervisor)
Abstract
The objective of this research is to model the wing structure of a flapping wing MAV and investigate structural dynamic behavior of its wing. in this research, to investigate and identify dynamic instabilities, modeling of the structure based on a nonlinear four-node plane element and aerodynamic modeling based on the strip theory in unsteady flow has been done, and by coupling these two models, the final model is formed. In the model of the wing structure, the displacement and changes angle inside the plane of the wing sections have been ignored and only outside the plane have been assumed for the degrees of freedom. In addition, the veins in the flapping wing have been omitted and the...