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CONTENTS
Volume 6, Number 4, December 2018
 

Abstract
A layerwise shear deformation theory is applied in this paper for buckling analysis of piezoelectric truncated conical shell. The core is a multiphase nanocomposite reinforced by carbon nanotubes (CNTs) and carbon fibers. The top and bottom face sheets are piezoelectric subjected to 3D electric field and external voltage. The Halpin-Tsai model is used for obtaining the effective moisture and temperature dependent material properties of the core. The proposed layerwise theory is based on Mindlin's first-order shear deformation theory in each layer and results for a laminated truncated conical shell with three layers considering the continuity boundary condition. Applying energy method, the coupled motion equations are derived and analyzed using differential quadrature method (DQM) for different boundary conditions. The influences of some parameters such as boundary conditions, CNTs weight percent, cone semi vertex angle, geometrical parameters, moisture and temperature changes and external voltage are investigated on the buckling load of the smart structure. The results show that enhancing the CNTs weight percent, the buckling load increases. Furthermore, increasing the moisture and temperature changes decreases the buckling load.

Key Words
buckling; piezoelectric truncated conical shells; multiphase nanocomposite; layerwise theory; hygrothermal load

Address
(1) Mohammad Hadi Hajmohammad, Ahmad Farrokhian:
Department of Mechanical Engineering, Imam Hossein University, Tehran, Iran;
(2) Mohammad Sharif Zarei:
Faculty of Engineering, Ayatollah Boroujerdi University, Boroujerd, Iran;
(3) Reza Kolahchi:
Department of Civil Engineering, Meymeh Branch, Islamic Azad University, Meymeh, Iran.

Abstract
The nonlinear free vibration of a nanorod subjected to finite strain is investigated. The governing equation of motion in material configuration in terms of displacement is determined. By means of Galerkin method, the Fourier series solutions satisfying some typical boundary conditions are determined. The amplitude-frequency relationship and interaction between the modes are studied. The effects of nonlocal elasticity are shown for different length of nanotubes and nonlocal parameter. The results show that nonlocal effects lead to additional internal modal interaction for nanorod vibrations.

Key Words
nonlocal elasticity; mode interactions; nonlocal elastic rod model; nonlinear axial vibration; finite strain

Address
(1) Mehmet Eren:
Institute of Science, Trakya University, 22030 Edirne, Turkey;
(2) Metin Aydogdu:
Department of Mechanical Engineering, Trakya University, 22030 Edirne, Turkey.

Abstract
In this article, the critical buckling of a single-walled carbon nanotube (SWCNT) embedded in Kerr's medium is studied. Based on the nonlocal continuum theory and the Euler-Bernoulli beam model. The governing equilibrium equations are acquired and solved for CNTs subjected to mechanical loads and embedded in Kerr's medium. Kerr-type model is employed to simulate the interaction of the (SWNT) with a surrounding elastic medium. A first time, a comparison with the available results is made, and another comparison between various models Winkler-type, Pasternak-type and Kerr-type is studied. Effects of nonlocal parameter and aspect ratio of length to diameter of nanobeam, as well as the foundation parameters on buckling of CNT are investigated. These results are important in the mechanical design considerations of nanocomposites based on carbon nanotubes.

Key Words
Kerr's medium; Euler-Bernoulli; buckling; carbon nanotubes; nanobeam

Address
(1) Khaled Bouakkaz:
Laboratory of Matérials et Hydrology, University of Sidi Bel Abbés, BP 89 Cité Ben M'hidi, 22000 Sidi Bel Abbés, Algeria;
(2) Tayeb Bensattalah, Khaled Bouakkaz, Mohamed Zidour, Tahar Hassaine Daouadji:
Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algeria;
(3) Tayeb Bensattalah, Mohamed Zidour, Tahar Hassaine Daouadji:
Laboratory of Geomatics and Sustainable Development, Ibn Khaldoun University of Tiaret, Algeria.

Abstract
Two dimensional (2D) atomic layered nanomaterials exhibit some of the most striking phenomena in modern materials research and hold promise for a wide range of applications including energy and biomedical technologies. Graphene has received much attention for having extremely high surface area to mass ratio and excellent electric conductivity. Graphene has also been shown to maximize the activity of surface-assembled metal nanoparticle catalysts due to its unique characteristics of enhancing mass transport of reactants to catalysts. This paper specifically investigates the strategy of pre-formed nanoparticle self-assembly used for the formation of various metal nanoparticles supported on graphene families such as graphene, graphene oxide, and reduced graphene oxide and aims at understanding the interactions between ligand-capped metal nanoparticles and 2D nanomaterials. By varying the functional groups on the ligands between alkyl, aromatic, amine, and alcohol groups, different interactions such as van der Waals, π-π stacking, dipole-dipole, and hydrogen bonding are formed as the 2D hybrids produced.

Key Words
nano-carbon; nanoparticle; nano-composites; nano-structures; nano-materials

Address
Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, USA.


Abstract
In the present investigation, thermal buckling and free vibration characteristics of functionally graded (FG) Timoshenko nanobeams subjected to nonlinear thermal loading are carried out by presenting a Navier type solution. The thermal load is assumed to be nonlinear distribution through the thickness of FG nanobeam. Thermo-mechanical properties of FG nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model and the material properties are assumed to be temperature-dependent. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton's principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the thermal buckling and vibration analysis of graded nanobeams including size effect. Moreover, in following a parametric study is accompanied to examine the effects of the several parameters such as nonlocal parameter, thermal effect, power law index and aspect ratio on the critical buckling temperatures and natural frequencies of the size-dependent FG nanobeams in detail. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared some cases in the literature. Also, it is found that the small scale effects and nonlinear thermal loading have a significant effect on thermal stability and vibration characteristics of FG nanobeams.

Key Words
thermal buckling; Timoshenko beam theory; vibration; functionally graded nanobeam; nonlocal elasticity theory

Address
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran.


Abstract
Unwanted vibration is an issue in many industrial systems, especially in nano-devices. There are many ways to compensate these unwanted vibrations based on the results of the past researches. Elastic medium and smart material etc. are effective methods to restrain unnecessary vibration. In this manuscript, dynamic analysis of viscoelastic nanosensor which is made of functionally graded (FGM) nanobeams is investigated. It is assumed that, the shaft is flexible. The system is modeled based on Timoshenko beam theory and also environmental condition, external linear varying loads and thermal loading effect are considered. The equations of motion are extracted by using energy method and Hamilton principle to describe the translational and shear deformation's behavior of the system. Governing equations of motion are extracted by supplementing Eringen's nonlocal theory. Finally vibration behavior of system especially the frequency of system is developed by implementation Semi-analytical differential transformed method (DTM). The results are validated in the researches that have been done in the past and shows good agreement with them.

Key Words
nanosensor; dynamic analysis; functionally graded material; viscoelastic material; linear varying loads; thermal loading effects; Eringen nonlocal theory

Address
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Postal code: 3414916818, Qazvin, Iran.



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