Techno Press
Tp_Editing System.E (TES.E)
Login Search

Volume 9, Number 3, October 2020

In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

Key Words
parametric instability; time dependent flow; smart materials; Bolotin

(1) Vahid Atabakhshian, Alireza Shooshtaria:
Department of Mechanical Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, I.R., Iran

This research is related to nonlinear stability analysis of advanced microbeams reinforced by Graphene Platelets (GPLs) considering generic geometrical imperfections and thermal loading effect. Uniform, linear and nonlinear distributions of GPLs in transverse direction have been considered. Imperfection sensitivity of post-bucking behaviors of the microbeam to different kinds of geometric imperfections have been examined. Geometric imperfection is first considered to be identical as the first buckling mode, then a generic function is employed to consider sine-type, local-type and global-type imperfectness. Modified couple stress theory is adopted to incorporate size-dependent behaviors of the beam at micro scale. The post-buckling problem is solved analytically to derive load-amplitude curves. It is shown that post-buckling behavior of microbeam is dependent on the type geometric imperfection and its magnitude. Also, post-buckling load can be enhanced by adding more GPLs or selecting a suitable distribution for GPLs.

Key Words
nonlinear stability; thermal load; graphene platelets; modified couple stress theory; nano-composite

(1) Raad M. Fenjan, Nadhim M. Faleh, Ridha A. Ahmed:
Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

The aim of this present research is the effect of the higher-order terms of the governing equation on the forced longitudinal vibration of a nanorod model and making comparisons of the results with classical nonlocal elasticity theory. For this purpose, the free axial vibration along with forced one under the two various linear and harmonic axial concentrated forces in zigzag Single-Walled Carbon Nanotube (SWCNT) are analyzed dynamically. Three various theories containing the classical theory, which is called Eringen's nonlocal elasticity, along with Rayleigh and Bishop theories (higher-order theories) are established to justify the nonlocal behavior of constitutive relations. The governing equation and the related boundary conditions are derived from Hamilton's principle. The assumed modes method is adopted to solve the equation of motion. For the free axial vibration, the natural frequencies are calculated for the various values of the nonlocal parameter only based on Eringen's theory. The effects of the nonlocal parameter, thickness, length, and ratio of the excitation frequency to the natural frequency over time in dimensional and non-dimensional axial displacements are investigated for the first time.

Key Words
forced vibration; Bishop theory; Rayleigh theory; carbon nanotube; axial vibration; assumed modes method

(1) Farshad Khosravi:
Department of Aerospace Engineering, K.N. Toosi University of Technology, Tehran, Iran
(2) Mahdi Simyari:
Department of Mechanical Engineering, University of Tehran, Tehran, Iran
(3) Seyed A. Hosseini:
Department of Industrial, Mechanical and Aerospace Engineering, Buein Zahra Technical University, Buein Zahra, Qazvin, Iran
(4) Abdelouahed Tounsi:
Yonsei Frontier Lab, Yonsei University, Seoul, Korea

Adsorption and heterogeneous electro-Fenton process using iron-loaded ZSM-5 nano-zeolite were investigated for the removal of Tetracycline (TC) from wastewater. The nano-zeolite was synthesized hydrothermally and modified through impregnation. The zeolite was characterized by XRD, FT-IR, FE-SEM, N2 adsorption-desorption, and NH3-TPD techniques. The equilibrium data were best represented by the Freundlich isotherm. The pseudo-second-order kinetic model was the most accurate model for the adsorption of TC on the modified nano-zeolite. The effect of parameters such as pH of solution and current density were investigated for the heterogeneous electro-Fenton process. The results showed that the current density of 150 mA and pH of 3 led to the highest TC removal (90.35%) at 50 min. The nano-zeolite showed the appropriate reusability. Furthermore, the developed kinetic model was in good agreement with the removal data of TC through the electro-Fenton process.

Key Words
adsorption; electro-Fenton; kinetic; nano-zeolite; pharmaceutical

(1) Hadi Adel Niaei, Mohammad Rostamizadeh:
Faculty of Chemical Engineering, Sahand University of Technology, Sahand New Town, Tabriz, Iran, P.O. Box: 51335-1996
(2) Hadi Adel Niaei, Mohammad Rostamizadeh:
Research Center of Environmental Engineering, Sahand University of Technology, Sahand New Town, Tabriz, Iran, P.O. Box: 51335-1996

The content of this study focuses on bending of flexoelectric Magneto-Electro-Elastic (MEE) nanobeams inserted within the foundation of Winkler-Pasternak according to nonlocal elasticity theory. Applying Hamilton's principle, the nonlocal nanobeams' governing equations in the framework higher order refined beam theory are attained and resolved through adapting an analytical solution. A parametric research is demonstrated for studying the effects that magneto-electro-mechanical loadings, the nonlocal parameter, flexoelectric, as well as the aspect ratio all have on the deflection properties of nanobeams. A discovery lead to beam geometrical parameters, the boundary conditions, flexoelectricity and nonlocal parameter partake substantial effects on nanoscale beams' dimensionless deflection.

Key Words
piezoelectric nanobeam; bending; flexoelectric; nonlocal elasticity theory; magneto-electric

(1) Ali Shariati:
Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
(2) Ali Shariati:
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
(3) Mahsa Karimiasl:
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran
(4) Rajendran Selvamani:
Department of Mathematics, Karunya University, Coimbatore, TamilNadu, India
(5) Ali Toghroli:
Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

In this research, beside presenting real images of produced Functionally Graded Carbon Nanotube-Reinforced Composites (FG-CNTRCs) and a brief review of the synthesis method of FG-CNTRCs, static and buckling analysis of FG-CNTRC with piezoelectric layers are investigated. It is assumed that the material properties of FG-CNTRC are varied through the thickness direction using four different distributions of Carbon Nanotubes (CNTs). To capture the size effects, nonlocal elasticity theory proposed by A.C. Eringen is also adopted in our model. One of the topics in our paper is using a higher order theory with eight different displacement fields and comparing their results with each other. To solve the governing equations, an analytical method is used to find the deflections and critical buckling loads of FG-CNTRCs. To show the accuracy of present methodology, our results are compared with the results of simply supported rectangular nano plates available in the literature. In this research, the effects of aspect ratio, piezoelectric layer and nonlocal parameter are also studied. It is hoped that this work leads to more accurate models on FG-CNTRC.

Key Words
functionally graded carbon nanotube-reinforced composite; nonlocal elasticity theory; bending; buckling; higher order shear deformation theory; Eight different displacement fields; piezoelectric layer

(1) Farshad Heidari, Ahmad Afsari:
Department of Mechanical Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran
(2) Maziar Janghorban:
Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran

This paper investigates the effect of linear and non-linear distribution of carbon nanotube volume fraction in the FG-CNTRC beams on the critical buckling by using higher-order shear deformation theories. Here, the material properties of the CNTRC beams are assumed to be graded in the thickness direction according to a new exponential power law distribution in terms of the carbon nanotube volume fractions. The single-walled carbon nanotube is aligned and distributed in the polymeric matrix with different patterns of reinforcement; the material properties of the CNTRC beams are described by using the rule of mixture. The governing equations are derived through using Hamilton's principle. The Navier solution method is used under the specified boundary conditions for simply supported CNTRC beams. The mathematical models provided in this work are numerically validated by comparison with some available results. New results of critical buckling with the non-linear distribution of CNT volume fraction in different patterns are presented and discussed in detail, and compared with the linear distribution. Several aspects of beam types, CNT volume fraction, exponent degree (n), aspect ratio, etc., are taken into this investigation. It is revealed that the influences of non-linearity distribution in the beam play an important role to improve the mechanical properties, especially in buckling behavior. The results show that the X-Beam configuration is the strongest among all different types of CNTRC beams in supporting the buckling loads.

Key Words
nanotube; critical buckling; shear deformation; volume fraction; FG-CNTRC; beam

(1) Rachid Zerrouki, Abdelkader Karas:
Faculty of Applied Sciences, Synthesis and Catalysis Laboratory LSCT, University of Tiaret, Algeria
(2) Mohamed Zidour:
Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2020 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-2-736-6801, Email: