Nonlinear free and forced vibration analysis of a single-walled carbon nanotube using shell model (original) (raw)
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Nonlinear vibrations and energy distribution of Single-Walled Carbon Nanotubes
The nonlinear vibrations of Single-Walled Carbon Nanotubes are analysed. The Sanders-Koiter elastic shell theory is applied in order to obtain the elastic strain energy and kinetic energy. The carbon nanotube deformation is described in terms of longitudinal, circumferential and radial displacement fields. The theory considers geometric nonlinearities due to large amplitude of vibration. The displacement fields are expanded by means of a double series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. The Rayleigh-Ritz method is applied in order to obtain approximate natural frequencies and mode shapes. Free boundary conditions are considered. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions. An energy approach based on the Lagrange equations is considered in order to obtain a set of nonlinear ordinary differential equations. The energy distribution of the system is studied by considering combinations of different vibration modes. The effect of the conjugate modes participation on the energy distribution is analysed.
Nonlinear Vibrations and Energy Distribution of Carbon Nanotubes
2014
The nonlinear vibrations of Single-Walled Carbon Nanotubes are analysed. The Sanders-Koiter thin shell theory is applied in order to obtain the elastic strain and kinetic energy. The carbon nanotube deformation is described in terms of axial, circumferential and radial displacement fields. The theory considers geometric nonlinearities due to large amplitude of vibration. The displacement fields are expanded by means of a double series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. The Rayleigh-Ritz method is applied to obtain approximate natural frequencies and mode shapes. Free boundary conditions are considered. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions. An energy approach based on the Lagrange equations is then considered to obtain a set of nonlinear ordinary differential equations. The total energy distribution of the shell is studied by consi...
Analysis of Nonlinear Vibrations for Multi-walled Carbon Nanotubes Embedded in an Elastic Medium
Nonlinear free vibration analysis of double-walled carbon nanotubes (DWCNTs) embedded in an elastic medium is studied in this paper based on classical (local) Euler-Bernoulli beam theory. Using the averaging method, the nonlinear free vibration responses of DWCNTs are obtained. The result is compared with the obtained results from the harmonic balance method for single-walled carbon nanotubes (SWCNTs) and DWCNTs. The effects of the surrounding elastic medium, van der waals (vdW) forces and aspect ratio of SWCNTs and DWCNTs on the vibration amplitude are discussed. The error percentage of the nonlinear free vibration frequencies between two theories decreases with increasing the spring constant of elastic medium. Results are also shown that if the value of the spring constant is lower than 7 3 10 / N m (7 3 10 / k N m ), the nonlinear free vibration frequencies are increased. In this case, the effect of the spring constant on frequency responses is significant, while if the value of the spring constant is higher than 9 3 10 / N m (9 3 10 / k N m ), the curve of frequency responses has a constant value near to 1 and therefore the effect of the spring constant on frequency responses is negligible.
Nonlinear dynamics of Single-Walled Carbon Nanotubes
The nonlinear vibrations of Single-Walled Carbon Nanotubes are analysed. The Sanders-Koiter elastic shell theory is applied in order to obtain the elastic strain energy and kinetic energy. The carbon nanotube deformation is described in terms of longitudinal, circumferential and radial displacement fields. The theory considers geometric nonlinearities due to large amplitude of vibration. The displacement fields are expanded by means of a double series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. The Rayleigh-Ritz method is applied to obtain approximate natural frequencies and mode shapes. Free boundary conditions are considered. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions. An energy approach based on the Lagrange equations is considered in order to obtain a set of nonlinear ordinary differential equations. The total energy distribution of the shell is studied by considering combinations of different vibration modes. The effect of the conjugate modes is analysed.
Low-frequency linear vibrations of single-walled carbon nanotubes: Analytical and numerical models
Journal of Sound and Vibration, 2014
Low-frequency vibrations of single-walled carbon nanotubes with various boundary conditions are considered in the framework of the Sanders-Koiter thin shell theory. Two methods of analysis are proposed. The first approach is based on the Rayleigh-Ritz method, a double series expansion in terms of Chebyshev polynomials and harmonic functions is considered for the displacement fields; free and clamped edges are analysed. This approach is partially numerical. The second approach is based on the same thin shell theory, but the goal is to obtain an analytical solution useful for future developments in nonlinear fields; the Sanders-Koiter equations are strongly simplified neglecting in-plane circumferential normal strains and tangential shear strains. The model is fully validated by means of comparisons with experiments, molecular dynamics data and finite element analyses obtained from the literature. Several types of nanotubes are considered in detail by varying aspect ratio, chirality and boundary conditions. The analyses are carried out for a wide range of frequency spectrum. The strength and weakness of the proposed approaches are shown; in particular, the model shows great accuracy even though it requires minimal computational effort.
Mechanics of Advanced Materials and Structures, 2018
In this article, vibration analysis of single-walled carbon nanotubes (SWCNTs) based on Love's thin shell theory has been investigated along with five sort of boundary conditions (S-S), (C-C), (C-F), (C-Sl), and (F-S). Three different shapes such as Armchair, Zigzag, and Chiral are taken into account under the influence of Winkler and Pasternak foundations. The wave propagation approach is employed to formulate the eigenvalue problem. MATLAB software package in used to obtain the vibrational natural frequencies of SWCNTs. The axial modal dependence is measured by the complex exponential functions implicating the axial modal numbers. Nomenclature E = Young's modulus h = shell thickness L = shell length v = Poisson's ratio ω = natural angular frequency E, v, ρ = effective material quantities L/R = length-to-radius ratio n = circumferential wave number Eh = in-plane rigidity ρh = mass density per unit lateral area θ = circumferential coordinate u(x, θ , t) = displacement functions in x direction v(x, θ , t) = displacement functions in θ direction w(x, θ , t) = displacement functions in z direction
Vibrations of Carbon Nanotubes: nonlinear models and energy distribution
Vibrations of Single-Walled Carbon Nanotubes for various boundary conditions are considered in the framework of the Sanders-Koiter thin shell theory. A double series expansion of displacement fields, based on the Chebyshev orthogonal polynomials and harmonic functions, is used to analyse numerically the natural frequencies of shells having free or clamped edges. A reduced form of the Sanders-Koiter theory is developed by assuming small circumferential and shear deformations; such approach allows to determine an analytical solution for the natural frequencies. The numerical model is validated with the results of molecular dynamics and finite element analyses present in literature. The analytical model is validated by means of comparisons with the numerical approach. Nonlinear vibrations and energy distribution of carbon nanotubes are then considered.
In the present paper, the comparison is conducted between three classical shell theories as applied to the linear vibrations of single-walled carbon nanotubes (SWCNTs); specifically, the evaluation of the natural frequencies is conducted via Donnell, Sanders and Flügge shell theories. The actual discrete SWCNT is modelled by means of a continuous homogeneous cylindrical shell considering equivalent thickness and surface density. In order to take into account the intrinsic chirality of carbon nanotubes (CNTs), a molecular based anisotropic elastic shell model is considered. Simply supported boundary conditions are imposed and complex method is applied to solve the equations of motion and to obtain the natural frequencies. Comparisons with the results of molecular dynamics simulations available in literature are performed to check the accuracy of the three different shell theories, where Flügge shell theory is found to be the most accurate. Then, a parametric analysis evaluating the e...
Applied Mathematical Modelling, 2012
Single-walled carbon nanotubes (SWCNTs) exhibit remarkable chirality-dependent mechanical phenomena. In present paper, an anisotropic elastic shell model is developed to study the vibration characteristics of chiral SWCNTs. Analytical solution is presented by using the Flügge shell theory and complex method. The suggested model is justified by a good agreement between the present results and some experimental and numerical available data in literature. Furthermore, the model is used to elucidate the effect of tube chirality on the frequencies of SWCNTs. Finally, the influences of the externally applied mid-face axial force and torque on longitudinal, radial and torsional frequencies of SWCNTs are investigated.
A molecular mechanics approach for the vibration of single-walled carbon nanotubes
Computational Materials Science, 2010
We investigate the vibrational properties of zigzag and armchair single-wall carbon nanotubes (CNTs) using the molecular mechanics approach. The natural frequencies of vibration and their associated intrinsic vibration modes are obtained. The simulations are carried out for four types of zigzag nanotubes (5, 0), (6, 0), (8, 0), (10, 0) and three types of armchair nanotubes (3, 3), (4, 4), (6, 6). The universal force field potential is used for the molecular mechanics approach. The first five natural frequencies are obtained for aspect ratios ranging from 5 to 20. The results indicate that the natural frequencies decrease as the aspect ratios increase. The results follow similar trends with results of previous studies for CNTs using structural mechanics approach.