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nonlocal-continuum-theory
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Study of Tunable Graphene Nano Resonator Vibration
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
In the present investigation, graphene sheets are simulated as Nano resonators using Kirchhoff plate theory and nonlocal continuum theory. External force and interlayer forces are simulated as harmonic and Winkler-like elastic foundation, respectively. Equations are solved analytically and numerically and corresponding results are presented. Considering a two layer resonator, natural frequencies and oscillation amplitude are investigated by free vibration and forced vibration analysis. Also, the effects of parameters such as small scale, sheets dimensions and inciting frequency on the vibration of the resonator, are displayed
On the theoretical and molecular dynamic methods for natural frequencies of multilayer graphene nanosheets incorporating nonlocality and interlayer shear effects
, Article Mechanics of Advanced Materials and Structures ; Volume 29, Issue 20 , 2022 , Pages 2873-2883 ; 15376494 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this paper, a multiplate nonlocal shear model and molecular dynamic simulations are presented to investigate the effects of interlayer shear and nonlocality on the natural frequencies of multilayer graphene sheets (MLGSs). From one aspect in the optimal design of such structures, the interaction between graphene layers, which can significantly vary the static and dynamic behavior due to lack of solidity of layers stack, should be considered. On the other hand, it is requied that the nonlocality phenomenon which has an effective role in the mechanical analysis of nanostructures is taken into account. To this aim, the equation of motion along with corresponding boundary conditions is...
Free vibration analysis of nanocones embedded in an elastic medium using a nonlocal continuum shell model
, Article International Journal of Engineering Science ; Volume 64 , 2013 , Pages 14-22 ; 00207225 (ISSN) ; Firouz Abadi, R. D ; Haddadpour, H ; Sharif University of Technology
2013
Abstract
The effect of elastic foundation on the free vibration characteristics of embedded nanocones is investigated in this paper. The nanocone is modeled as a thin shell and the nonlocal elasticity theory is used to derive the governing equations of motion. Also the elastic medium is simulated using Winkler and Pasternak foundation models. Based on the modal analysis technique and applying the Galerkin method the governing equations are solved to obtain the natural frequencies. The drawn results emphasis the effects of geometry and small-scale parameter on the natural frequencies of nanocone. Also the effect of elastic foundation modulus on the resonance frequencies of the nanocones are studied...
A Gradient-Enhanced Computational Homogenization Technique for Multi-Scale Modeling of Heterogeneous Materials with Softening Behavior
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The use of conventional multi-scale models for materials that exhibit softening behavior is not possible due to the phenomenon of localization, because the fundamental assumptions of homogenization are no longer satisfying around the localization region, and therefore the macro-scale results depend on the size of the representative volume element and the macro-scale mesh discretization. Also, if the finite elements mesh be fine enough, the solution does not converge to acceptable physical values. This research concerns the multi-scale study of failure and proposes an appropriate method for computational homogenization of that. The main idea is to apply the enhanced homogenization method to...
Developing Classical and Nonlocal Interlayer Shear Models for Free Vibration Analysis of Multilayer Graphene Plates
, Ph.D. Dissertation Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Experimental observations on multilayer graphene structures show that interlayer interactions including compressive and shear effects between layers are very important in their mechanical behavior. Existing analytical investigations have generally addressed the issue of pressure interactions between layers using interatomic potentials, while the models which consider the interlayer shear effect are rarely found in the literature. To address this shortcoming, this thesis presents a new formulation for multilayer graphene structures with desired shapes and boundaries, taking into account the interlayer shear effect according to the classical continuum mechanics theory. Next, size-dependent...
In-plane and out-of-plane waves in nanoplates immersed in bidirectional magnetic fields
, Article Structural Engineering and Mechanics ; Volume 61, Issue 1 , 2017 , Pages 65-76 ; 12254568 (ISSN) ; Gharebaghi, S. A ; Mehri, B ; Sharif University of Technology
Techno Press
2017
Abstract
Prediction of the characteristics of both in-plane and out-of-plane elastic waves within conducting nanoplates in the presence of bidirectionally in-plane magnetic fields is of interest. Using Lorentz's formulas and nonlocal continuum theory of Eringen, the nonlocal elastic version of the equations of motion is obtained. The frequencies as well as the corresponding phase and group velocities pertinent to the in-plane and out-of-plane waves are analytically evaluated. The roles of the strength of in-plane magnetic field, wavenumber, wave direction, nanoplate's thickness, and small-scale parameter on characteristics of waves are discussed. The obtained results show that the in-plane...
Nonlinear dynamic analysis of SWNTs conveying fluid using nonlocal continuum theory
, Article Structural Engineering and Mechanics ; Volume 66, Issue 5 , 10 June , 2018 , Pages 621-629 ; 12254568 (ISSN) ; Mousavi, T ; Bahai, H ; Sharif University of Technology
Techno Press
2018
Abstract
By employing the nonlocal continuum field theory of Eringen and Von Karman nonlinear strains, this paper presents an analytical model for linear and nonlinear dynamics analysis of single-walled carbon nanotubes (SWNTs) conveying fluid with different boundary conditions. In the linear analysis the natural frequencies and critical flow velocities of SWNTs are computed. However, in the nonlinear analysis the effect of nonlocal parameter on nonlinear dynamics of cantilevered SWNTs conveying fluid is investigated by using bifurcation diagram, phase plane and Poincare map. Numerical results confirm existence of chaos as well as a period-doubling transition to chaos. Copyright © 2018 Techno-Press,...
Magneto-mechanical stability of axially functionally graded supported nanotubes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; Mirtalebi, H ; Ahmadian, M. T ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
In this paper, size-dependent vibration analysis of axially functionally graded (AFG) supported nanotubes conveying nanoflow under longitudinal magnetic fields are performed, aiming at performance improvement of fluid-interaction nanosystems. Either the density or the elastic modulus of the AFG nanotube varies linearly or exponentially along the axial direction. Based on the nonlocal continuum theory, the higher-order dynamical equation of motion of the system is derived considering no-slip boundary condition. Galerkin discretization technique and eigenvalue analysis are implemented to solve the modeled equation. The validity of the simplified model is justified by comparing the results with...
Magneto-mechanical stability of axially functionally graded supported nanotubes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; Mirtalebi, H ; Ahmadian, M. T ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
In this paper, size-dependent vibration analysis of axially functionally graded (AFG) supported nanotubes conveying nanoflow under longitudinal magnetic fields are performed, aiming at performance improvement of fluid-interaction nanosystems. Either the density or the elastic modulus of the AFG nanotube varies linearly or exponentially along the axial direction. Based on the nonlocal continuum theory, the higher-order dynamical equation of motion of the system is derived considering no-slip boundary condition. Galerkin discretization technique and eigenvalue analysis are implemented to solve the modeled equation. The validity of the simplified model is justified by comparing the results with...
On the theoretical and molecular dynamic methods for natural frequencies of multilayer graphene nanosheets incorporating nonlocality and interlayer shear effects
, Article Mechanics of Advanced Materials and Structures ; 2021 ; 15376494 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Bellwether Publishing, Ltd
2021
Abstract
In this paper, a multiplate nonlocal shear model and molecular dynamic simulations are presented to investigate the effects of interlayer shear and nonlocality on the natural frequencies of multilayer graphene sheets (MLGSs). From one aspect in the optimal design of such structures, the interaction between graphene layers, which can significantly vary the static and dynamic behavior due to lack of solidity of layers stack, should be considered. On the other hand, it is requied that the nonlocality phenomenon which has an effective role in the mechanical analysis of nanostructures is taken into account. To this aim, the equation of motion along with corresponding boundary conditions is...