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Tadi Beni Y.,Shahrekord University | Abadyan M.,Islamic Azad University | Koochi A.,Islamic Azad University at Naein
Physica Scripta | Year: 2011

In this paper, the effect of the Casimir attraction on the torsion/bending coupled pull-in instability of an electrostatic nano-actuator has been investigated for the first time. The governing equation of the actuator is derived and the instability parameters of the nano-actuator have been computed as a function of the geometrical characteristics and the bending/torsion stiffness ratio of the nano-actuator. The results reveal that the Casimir attraction could highly affect the coupled pull-in performance of the actuator. It is found that the Casimir force can reduce the instability voltage of nano-actuators. This deteriorating effect is more clearly highlighted in the torsional pull-in mode compared to the bending pull-in mode. Furthermore, it is found that the influence of the Casimir force on pull-in angle and deflection of the torsional actuator depends on the torsion/bending coupling ratio. For small-gap torsional actuators, the pull-in parameters have been strongly affected by the Casimir force, and neglecting Casimir attraction may lead to considerable error during simulations of the pull-in instability. The results of the present model are in better agreement with the experimental data compared to previous models. © 2011 The Royal Swedish Academy of Sciences. Source

Tadi Beni Y.,Shahrekord University | Koochi A.,Islamic Azad University at Naein | Abadyan M.,Islamic Azad University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

In this paper, the static pull-in instability of beam-type nano-electromechanical systems (NEMS) is theoretically investigated considering the effect of Casimir attraction, elastic boundary conditions (BC) and size dependency. Rotational springs are utilized at each of the supported ends of the simply and doubly supported beams to model an elastic BC. The modified couple stress theory is applied to examine the size effects on the instability of nanostructures. In order to solve the nonlinear constitutive equation of nano-beams, modified Adomian decomposition (MAD) as well as the numerical method is employed. The results reveal significant influences of Casimir attraction, elastic BC and size dependency on the pull-in characteristics of NEMS. The obtained MAD solution agrees well with the numerical one. © 2010 Elsevier B.V. All rights reserved. Source

Koochi A.,Islamic Azad University at Naein | Noghrehabadi A.,Shahid Chamran University | Abadyan M.,Islamic Azad University
International Journal of Modern Physics B | Year: 2011

Beam-type nano-electromechanical system (NEMS) is one of the most components in constructing nano-devices. Herein, a distributed parameter model is used to study the influence of van der Waals (vdW) attraction on the pull-in performance of the cantilever NEMS. Homotopy perturbation method (HPM) is applied to solve the nonlinear governing equation of the actuators in the form of convergent series. Moreover, analytical results are compared with those of numerical method as well as a lumped parameter model. The pull-in voltage and critical cantilever tip deflection of NEMS are determined. Results depict that vdW attraction decreases the pull-in deflection and voltage of the NEMS. On the other hand, the fringing field increases the pull-in deflection while decreases the pull-in voltage of the system. The analytical results have good agreement with numerical results and those available in the literature. © 2011 World Scientific Publishing Company. Source

Abadyan M.,Islamic Azad University at Naein | Bagheri R.,Sharif University of Technology | Kouchakzadeh M.A.,Sharif University of Technology | Hosseini Kordkheili S.A.,Sharif University of Technology
Materials and Design | Year: 2011

In this paper, tensile strain energy absorption of two different hybrid modified epoxies has been systematically investigated. In one system, epoxy has been modified by amine-terminated butadiene acrylonitrile (ATBN) and hollow glass spheres as fine and coarse modifiers, respectively. The other hybrid epoxy has been modified by the combination of ATBN and recycled Tire particles. The results of fracture toughness measurement of blends revealed synergistic toughening for both hybrid systems in some formulations. However, no evidence of synergism is observed in tensile test of hybrid samples. Scanning electron microscope (SEM), transmission optical microscope (TOM) and finite element (FEM) simulation were utilized to study deformation mechanisms of hybrid systems in tensile test. It is found that coarse particles induce stress concentration in hybrid samples. This produces non-uniform strain localized regions which lead to fracture of hybrid samples at lower tensile loading and energy absorption levels. © 2011. Source

Koochi A.,Islamic Azad University at Naein | Kazemi A.S.,Islamic Azad University | Noghrehabadi A.,Shahid Chamran University | Yekrangi A.,Islamic Azad University | Abadyan M.,Islamic Azad University
Materials and Design | Year: 2011

Modeling the buckling of multi walled carbon nanotube (MWCNT) probes/actuators in the vicinity of thin and thick graphite has been carried out for the first time via two analytical approximation methods as well as a numerical one. A hybrid nano-scale continuum model based on Lennard-Jones potential is applied to simulate the intermolecular force-induced deflection of MWCNT. The critical values of MWCNT tip deflection and MWCNT-graphite attraction at the onset of the instability are computed. In addition, minimum nanotube-graphite initial gap and stable length of freestanding CNT are determined as basic parameters for engineering applications and nano-devices design. The stable length of MWCNT is determined as a function of its geometrical and material characteristics, initial gap and number of graphene layers. © 2011. Source

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