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


scs
 
CONTENTS
Volume 36, Number 6, September25 2020
 

Abstract
The purpose of this paper is to depict the effect of rotation and initial stress on a magneto-thermoelastic medium with diffusion. The problem discussed within memory-dependent derivative in the context of the three-phase-lag model (3PHL), Green-Naghdi theory of type III (G-N III) and Lord and Shulman theory (L-S). Analytical expressions of the considered variables are obtained by using Laplace-Fourier transforms technique. Numerical results for the field quantities given in the physical domain and illustrated graphically in the absence and presence of a magnetic field, initial stress as well as the rotation. The differences in variable thermal conductivity are also presented at different parameter of thermal conductivity. The numerical results of the field variables are presented graphically to discuss the effect of various parameters of interest. Some special cases are also deduced from the present investigation.

Key Words
diffusion; rotation; initial stress; variable thermal conductivity; memory-dependent derivative

Address
Samia M. Said and Mohamed I.A. Othman: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Elsayed M. Abd-Elaziz: Ministry of Higher Education, Zagazig Higher Institute of Eng. & Tech., Zagazig, Egypt

Abstract
This paper studies nonlinear stability behavior of a nanocrystalline silicon curved nanoshell considering strain gradient size-dependency. Nanocrystallines are composite materials with an interface phase and randomly distributed nano-size grains and pores. Imperfectness of the curved nanoshell has been defined based on an initial deflection. The formulation of nanocrystalline nanoshell has been established by thin shell theory and an analytical approach has been used in order to solve the buckling problem. For accurately describing the size effects related to nano-grains or nano-pores, their surface energies have been included. Nonlinear stability curves of the nanoshell are affected by the size of nano-grain, curvature radius and nano-pore volume fraction. It is found that increasing the nano-pore volume fraction results in lower buckling loads.

Key Words
nanocrystalline material; nonlinear stability; porous nanoshell; Strain gradient; Mori-Tanaka scheme

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

Abstract
This article presents a comprehensive static analysis of simply supported cross-ply carbon nanotubes reinforced composite (CNTRC) laminated nanobeams under various loading profiles. The nonlocal strain gradient constitutive relation is exploited to present the size-dependence of nano-scale. New higher shear deformation beam theory with hyperbolic function is proposed to satisfy the zero-shear effect at boundaries and parabolic variation through the thickness. Carbon nanotubes (CNTs), as the reinforced elements, are distributed through the beam thickness with different distribution functions, which are, uniform distribution (UD-CNTRC), V- distribution (FG-V CNTRC), O- distribution (FG-O CNTRC) and X- distribution (FG-X CNTRC). The equilibrium equations are derived, and Fourier series function are used to solve the obtained differential equation and get the response of nanobeam under uniform, linear or sinusoidal mechanical loadings. Numerical results are obtained to present influences of CNTs reinforcement patterns, composite laminate structure, nonlocal parameter, length scale parameter, geometric parameters on center deflection ad stresses of CNTRC laminated nanobeams. The proposed model is effective in analysis and design of composite structure ranging from macro-scale to nano-scale.

Key Words
static and stress analysis; Nonlocal strain gradient theory; hyperbolic shear deformation theory; carbon nanotubes reinforced nanobeams; fourier series

Address
Ahmed Amine Daikh: Department of Civil Engineering, Laboratoire d\'Etude des Structures et de Meecanique des Mateeriaux, Mascara, Algeria;
Mechanics of Structures and Solids Laboratory, Faculty of Technology, University of Sidi Bel Abbes, Sidi Bel Abbes, Algeria
Ahmed Drai:Department of Mechanical Engineering, Mustapha STAMBOULI, University of Mascara, 29000, Algeria;
LABAB Laboratory of ENPO, Oran, 31000, Algeria
Mohamed Sid Ahmed Houari: Department of Civil Engineering, Laboratoire d\'Etude des Structures et de Meecanique des Mateeriaux, Mascara, Algeria
Mohamed A. Eltaher: Faculty of Engineering, Department of Mechanical Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia;
Faculty of Engineering, Department of Mechanical Design and Production, Zagazig University, P.O. Box 44519, Zagazig, Egypt





Abstract
This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.

Key Words
reactive powder concrete; metakaolin; pozzolanic activity; spalling properties; fire resistance

Address
Hongseok Jang, Jebang Yi and Seungyoung So: Department of Architectural Engineering, Research Center of Industrial Technology, Jeonbuk National University,
567 Baekje-daero, deokjin-gu, Jeonju 54896, Republic of Korea


Abstract
The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov\'s foundation. To this end, first, displacement field\'s equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier\'s analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

Key Words
sandwich beam; Shape memory alloy; Buckling and bending; Porosity; Higher-order shear deformation theory; Vlasov\'s foundation

Address
Mostafa Bamdad, Mehdi Mohammadimehr and Kazem Alambeigi: Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan
P.O Box 87317-53153, Kashan, Iran


Abstract
The current study deals with the size-dependent free vibration analysis of graphene nanoplatelets (GNPs) reinforced polymer nanocomposite plates resting on Pasternak elastic foundation containing different boundary conditions. Based on a four variable refined shear deformation plate theory, which considers shear deformation effect, in conjunction with the Eringen nonlocal elasticity theory, which contains size-dependency inside nanostructures, the equations of motion are established through Hamilton\'s principle. Moreover, the effective material properties are estimated via the Halpin-Tsai model as well as the rule of mixture. Galerkin\'s mathematical formulation is utilized to solve the equations of motion for the vibrational problem with different boundary conditions. Parametrical examples demonstrate the influences of nonlocal parameter, total number of layers, weight fraction and geometry of GNPs, elastic foundation parameter, and boundary conditions on the frequency characteristic of the GNPs reinforced nanoplates in detail.

Key Words
free vibration; nanocomposites; reinforcement; Graphene nanoplatelet; boundary conditions

Address
Behrouz Karami and Davood Shahsavari: Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran
Ali Ordookhani: Department of Civil Engineering, School of Science and Engineering, Sharif University of Technology,
International Campus, P.O. Box 79417-76655, Kish Island, Iran
Ali Ordookhani: Department of Civil Engineering, School of Science and Engineering, Sharif University of Technology,
International Campus, P.O. Box 79417-76655, Kish Island, Iran
Parastoo Gheisari: School of Mechanical Engineering, Shiraz University, Shiraz, Iran
Li Li: State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering,
Huazhong University of Science and Technology, Wuhan 430074, China
Arameh Eyvazian: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam;
Faculty of Electrical – Electronic Engineering, Duy Tan University, Da Nang 550000, Vietnam





Abstract
This paper presents numerical and theoretical investigations on the strain rate in steel-concrete composite (SC) panels under low-velocity impact of a hemispherical rigid body. Finite element analyses were performed on five specimens with different loading rates. The impact energy was kept constant to eliminate its influence by simultaneously altering the velocity and mass of the projectile. Results show that the strain rate in most parts of the specimens was low and its influence on bearing capacity and energy dissipation was limited in an average sense of space and time. Therefore, the strain rate effect can be ignored for the analyses of global deformation. However, the strain rate effect should be considered in local contact problems. Equations of the local strain and strain rate were theoretically derived.

Key Words
steel-concrete composite panel; finite element analysis; low-velocity impact; strain rate; theoretical method

Address
Weiyi Zhao, Guotao Yang, Ziguo Wang and Zepeng Gao: Department of Civil Engineering, Qingdao University of Technology, Qingdao 266033, Shandong, China
2Beihang School, Beihang University, Beijing 100191, China
Lin Wan: Beihang School, Beihang University, Beijing 100191, China
Quanquan Guo: School of Transportation Science and Engineering, Beihang University, Beijing 100191, China


Abstract
In the present research, the free vibration analysis of functionally graded (FG) nanocomposite deep spherical shells reinforced by graphene platelets (GPLs) on elastic foundation is performed. The elastic foundation is assumed to be Winkler-Past ernak-type. It is also assumed that graphaene platelets are randomly oriented and uniformly dispersed in each layer of the nanocomposite shell. Volume fraction of the graphene platelets as nanofillers may be different in the layers. The modified HalpinTsai model is used to approximate the effective mechanical properties of the multilayer nanocomposite. With the aid of the first order shear deformation shell theory and implementing Hamilton\'s principle, motion equations are derived. Afterwards, the generalized differential quadrature method (GDQM) is utilized to study the free vibration characteristics of FG-GPLRC spherical shell. To assess the validity and accuracy of the presented method, the results are compared with the available researches. Finally, the natural frequencies and corresponding mode shapes are provided for different boundary conditions, GPLs volume fraction, types of functionally graded, elastic foundation coefficients, opening angles of shell, and thickness-to-radius ratio.

Key Words
spherical shell; graphene platelets; GDQM; nanocomposite

Address
Arameh Eyvazian: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam;
Faculty of Electrical – Electronic Engineering, Duy Tan University, Da Nang 550000, Vietnam
Farayi Musharavati: Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, P.O. Box 2713, Doha, Qatar
Pouyan Talebizadehsardari: Metamaterials for Mechanical, Biomechanical and Multiphysical Applications Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
Tamer A. Sebaey: Engineering Management Department, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia;
Mechanical Design and Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Sharkia, Egypt





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: info@techno-press.com