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Micromechanical analysis of unidirectional polymeric composites material with triangular fibers
F. Barati,E. Torabi,H. Veiskarami,A. Khanbabaea Nava,M. M. Attar 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10
The purpose of this study is to investigate the mechanism of load transfer in unidirectional polymeric composites material with triangular fibers in the presence of broken fibers. It is assumed that all fibers with triangle-cross section lie in a same direction while loaded by a load at infinity. In previous studies, the behavior of polymeric matrix is assumed elastic, while the behavior of most polymeric matrix is elastic-perfect plastic. For this purpose, equilibrium equations by use of shear-lag theory have been derived and by proper using boundary and boundness conditions, displacement field and stress distribution were computed. Finally, the results of stress concentrations and di shear stress, at neighbor of broken fibers for carbon-epoxy composite material were extracted and compared with composite materials with circular fibers. The analytical results are compared to the detailed finite element values. A close match is observed between the two methods.
Ebrahimi, Farzad,Barati, Mohammad Reza,Zenkour, Ashraf M. The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.2
Free vibration analysis is presented for a simply-supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen's nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher order shear deformation beam theory where coupled equations obtained using Hamilton's principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.
Some exact and new solutions of the Nizhnik-Novikov-Vesselov equation using the Exp-function method
Shin, B.C.,Darvishi, M.T.,Barati, A. Pergamon Press ; Elsevier Science Ltd 2009 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.58 No.11
In this paper, using the Exp-function method, we give some explicit formulas of exact traveling wave solutions for the Nizhnik-Novikov-Vesselov equation.
Farzad Ebrahimi,Mohammad Reza Barati,Ashraf M. Zenkour 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.2
Free vibration analysis is presented for a simply-supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen’s nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher order shear deformation beam theory where coupled equations obtained using Hamilton’s principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.
The Effect of Anisotropy on Thin-Walled Tube Bending
K. Hasanpour,B. Amini,M. Poursina,M. Barati 한국소성가공학회 2011 기타자료 Vol.2011 No.8
Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. The rotary-draw-bending method which is a complex physical process with multi-factor interactive effects is one of the advanced tube forming processes with high efficiency, high forming precision, low consumption and good flexibility for bending angle changes. However it may produce a wrinkling phenomenon, over thinning and cross-section distortion if the process parameters are inappropriate. Wrinkles propagate permanently in thin-walled tube, but finally, localize in a finite zone and lead to failure. The prediction of wrinkling in thin-walled tube bending processes has been a challenging topic. In this paper, firstly, the plastic deforming behavior and wrinkling mechanism for a thin-walled tube is simulated and the results will compare with the available experimental ones. Then, the effect of anisotropy on ovalization, thickness and wrinkling of tube will be investigated using FEM. Extensive numerical results are presented showing the effects of the various kinds of materials and geometric parameters on wrinkling using anisotropic yield function.
Seyed Sajad Mirjavadi,Masoud Forsat,Mohammad Reza Barati,A.M.S. Hamouda 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.4
Based on third-order shear deformation shell theory, the present paper investigates post-buckling properties of eccentrically stiffened metal foam curved shells/panels having initial geometric imperfectness. Metal foam is considered as porous material with uniform and non-uniform models. The single-curve porous shell is subjected to in-plane compressive loads leading to post-critical stability in nonlinear regime. Via an analytical trend and employing Airy stress function, the nonlinear governing equations have been solved for calculating the post-buckling loads of stiffened geometrically imperfect metal foam curved shell. New findings display the emphasis of porosity distributions, geometrical imperfectness, foundation factors, stiffeners and geometrical parameters on post-buckling properties of porous curved shells/panels.
Seyed Sajad Mirjavadi,Masoud Forsat,Mohammad Reza Barati,A.M.S. Hamouda 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.6
Based on a refined shear deformation finite strip, transient vibrations of graphene oxide powder (GOP) reinforced plates due to external pulse loads have been investigated. The plate has uniformly and linearly distributed GOPs inside material structure. Applied pulse loads have been selected as sinusoidal, linear and blast types. Such pulse loads result in transient vibrations of the GOP-reinforced plates which are not explored before. Finite strip method (FSM) has been performed for solving the equations of motion and then inverse Laplace transform technique has been employed to derive transient responses due to pulse loading. It is reported in this study that the transient responses of GOP-reinforced plates are dependent on GOP dispersions, GOP volume fraction, type of pulse loading, loading time and load locations.
Seyed Sajad Mirjavadi,Masoud Forsat,Mohammad Reza Barati,A.M.S. Hamouda 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.1
A multi-scale epoxy/CNT/fiberglass annular sector plate is studied in this paper in the view of determining nonlinear forced vibration characteristics. A 3D Mori-Tanaka model is employed for evaluating multi-scale material properties. Thus, all of glass fibers are assumed to have uni-direction alignment and CNTs have random diffusion. The geometry of annular sector plate can be described based on the open angle and the value of inner/outer radius. In order to solve governing equations and derive exact forced vibration curves for the multi-scale annular sector, Jacobi elliptic functions are used. Obtained results demonstrate the significance of CNT distribution, geometric nonlinearity, applied force, fiberglass volume, open angle and fiber directions on forced vibration characteristics of multi-scale annular sector plates.
The Role of External Defects in Chemical Sensing of Graphene Field-Effect Transistors
Kumar, B.,Min, K.,Bashirzadeh, M.,Farimani, A. Barati,Bae, M.-H.,Estrada, D.,Kim, Y. D.,Yasaei, P.,Park, Y. D.,Pop, E.,Aluru, N. R.,Salehi-Khojin, A. American Chemical Society 2013 Nano letters Vol.13 No.5
<P>A fundamental understanding of chemical sensing mechanisms in graphene-based chemical field-effect transistors (chemFETs) is essential for the development of next generation chemical sensors. Here we explore the hidden sensing modalities responsible for tailoring the gas detection ability of pristine graphene sensors by exposing graphene chemFETs to electron donor and acceptor trace gas vapors. We uncover that the sensitivity (in terms of modulation in electrical conductivity) of pristine graphene chemFETs is not necessarily intrinsic to graphene, but rather it is facilitated by external defects in the insulating substrate, which can modulate the electronic properties of graphene. We disclose a mixing effect caused by partial overlap of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of adsorbed gas molecules to explain graphene’s ability to detect adsorbed molecules. Our results open a new design space, suggesting that control of external defects in supporting substrates can lead to tunable graphene chemical sensors, which could be developed without compromising the intrinsic electrical and structural properties of graphene.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-5/nl304734g/production/images/medium/nl-2012-04734g_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl304734g'>ACS Electronic Supporting Info</A></P>