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Subsonic and supersonic flow-induced vibration of sandwich cylindrical shells with FG-CNT reinforced composite face sheets and metal foam core
, Article International Journal of Mechanical Sciences ; Volume 215 , 2022 ; 00207403 (ISSN) ; Fallah, F ; Ahmadian, M. T ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Based on the linear fluid-solid interaction (FSI) model and classical shell theories, vibration behavior of sandwich cylindrical shells subjected to external incompressible or compressible fluid flow is investigated. The sandwich shell includes the same outer and inner face sheets made of carbon nanotube (CNT) reinforced composites and a metal foam core. The effective mechanical properties of CNT reinforced composites are obtained using the extended rule of mixture. Also, the porosity distribution through the foam thickness is assumed to be in the form of a trigonometric function. Equations of motion and corresponding boundary conditions are derived according to the Donnell's, Love's and...
Investigation of Local Buckling in Marine Pipelines under External Pressure
, M.Sc. Thesis Sharif University of Technology ; Fallah Rajabzadeh, Famida (Supervisor) ; Seef, Mohammad Saeed (Co-Advisor)
Abstract
To keep up with the growing demands for energy, the oil and gas industry ventures into deeper waters. This increases complexity of offshore projects. Part of this complexity is due to the resistance of a pipeline against local buckling collapse due to external pressure that is more significant in higher pipe laying depth and consequently higher external pressure. Pipeline response to external pressure is an important factor in design of marine pipeline.Local buckling of a pipeline is the buckling behaviour within the pipeline cross section. Other types of buckling behaviour such as upheaval and lateralbuckling are not in the scope of this thesis.In this thesis, the installing pipeline is...
An analytical solution for dynamic behavior of thick doubly curved functionally graded smart panels
, Article Composite Structures ; Vol. 107, issue , January , 2014 , p. 88-102 ; Askari Farsangi, M. A ; Sharif University of Technology
Abstract
In this paper, an analytical solution is presented for free vibration and dynamic behavior of doubly curved laminated shell consisting of a functionally graded core layer and surface attached functionally graded piezoelectric layers. Shell through-thickness kinematics is based on higher order shear deformation theory of shells, whereas a quadratic variation is assumed for electric potential. Using Hamilton's principle and Maxwell's equation, the governing equations of motion under mechanical loads are derived as seven highly coupled partial differential equations. Implementing Laplace transformation, doing few mathematical operations and using Laplace inverse method, time dependencies of...
Free Vibration and Buckling Analysis of a Laminated Composite Cylinder Made of Functionally Graded Material with Lengthwise Properties Variation Including Thermal Effects
, M.Sc. Thesis Sharif University of Technology ; Kargarnovin, Mohammad Hossein (Supervisor)
Abstract
In recent decades, employing fiber-reinforced composite has growing field in various industries due to distinct features like high specific stiffness and strength. Studies in case of this type of composite have not been stopped and nowadays, widespread researches are conducted over optimization of them. As a result, the effect of distributing fiber in this composite by taking the concept of functionally graded materials, on vibrations and buckling behaviors including natural frequencies and minimum axial bulking load under different boundary conditions for a multi-layered cylindrical shell in which volume fraction of fiber along its length varies according to power-law model are investigated...
Vibration and Buckling Analysis of Multi-walled Carbon Nanocone by Molecular Mechanics Approach and Stability Analysis of Carbon Nanocone Conveying Fluid
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
In this thesis, vibration analysis of multi-walled carbon nanoconesstudied by molecular mechanics approach. In this simulation, atoms of carbon and bondings of them modeled by concentrated mass and structural elements, respectively and then mode shapes and natural frequencies of these structures calculated and effects of height, apex angle, boundary conditions and number of layers on natural frequencies of carbon nanocones studied. Also, critical buckling load of multi-walled carbon nanocones due to axial and in-plane loads obtained and effects of height, apex angle and number of layers on critical buckling loads of carbon nanocones studied. These results validated by molecular dynamics and...
Torsional instability of carbon nano-peapods based on the nonlocal elastic shell theory
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 47 , 2013 , Pages 316-323 ; 13869477 (ISSN) ; Rafati, J ; Naghdabadi, R ; Sharif University of Technology
2013
Abstract
In this paper a shell formulation is proposed for analyzing the torsional instability of carbon nano-peapods (CNPs), i.e., the hybrid structures composed of C60 fullerenes encapsulated inside carbon nanotubes (CNTs), based on the nonlocal elasticity theory. The nonlocal elasticity theory, as a well-known non-classical continuum theory, is capable to capture small scale effects which appear due to the discontinuities in nano-structures. Based on the derived formulation, the critical torsional moments for a pristine (10,10) CNT and C60@ (10,10) CNP are investigated as case studies. The results for the (10,10) CNT are compared with those of the available molecular dynamics simulations in the...
On dynamic instability of a pressurized functionally graded carbon nanotube reinforced truncated conical shell subjected to yawed supersonic airflow
, Article Composite Structures ; Volume 153 , 2016 , Pages 938-951 ; 02638223 (ISSN) ; Asadi, H ; Wang, Q ; Sharif University of Technology
Elsevier Ltd
Abstract
The aeroelastic flutter characteristics of a functionally graded carbon nanotube reinforced composite (FG-CNTRC) truncated conical shell under simultaneous actions of a hydrostatic pressure and yawed supersonic airflow are scrutinized. The nonlinearity in geometry of the conical shell is considered in Green–Lagrange sense and the model is derived according to the Novozhilov nonlinear shell theory. The aerodynamic pressure is modeled based on the quasi-steady Krumhaar's modified supersonic piston theory by considering the effect of the panel curvature and flow yaw angle. Parametric studies are conducted to investigate the effects of boundary conditions, semi-vertex angle, distribution and...
Post-buckling analysis of geometrically imperfect nanoparticle reinforced annular sector plates under radial compression
, Article Computers and Concrete ; Volume 26, Issue 1 , 2020 , Pages 21-30 ; Forsat, M ; Mollaee, S ; Barati, M. R ; Afshari, B. M ; Hamouda, A. M. S ; Sharif University of Technology
Techno-Press
2020
Abstract
Buckling and post-buckling behaviors of geometrically imperfect annular sector plates made from nanoparticle reinforced composites have been investigated. Two types of nanoparticles are considered including graphene oxide powders (GOPs) and silicone oxide (SiO2). Nanoparticles are considered to have uniform and functionally graded distributions within the matrix and the material properties are derived using Halpin-Tsai procedure. Annular sector plate is formulated based upon thin shell theory considering geometric nonlinearity and imperfectness. After solving the governing equations via Galerkin’s technique, it is showed that the post-buckling curves of annular sector plates rely on the...
Thermoelastic analysis of thick-walled finite-length cylinders of functionally graded materials
, Article Journal of Thermal Stresses ; Volume 28, Issue 4 , 2005 , Pages 391-408 ; 01495739 (ISSN) ; Angoshtari, A ; Naghdabadi, R ; Sharif University of Technology
2005
Abstract
A semianalytical thermoelasticity solution for thick-walled finite-length cylinders made of functionally graded (FG) materials is presented. The governing partial differential equations are reduced to ordinary differential equations using Fourier expansion series in the axial coordinate. The radial domain is divided into some virtual subdomains in which the power-law distribution is used for the thermomechanical properties of the constituent components. Imposing the necessary continuity conditions between adjacent subdomains, together with the global boundary conditions, a set of linear algebraic equations are obtained. Solution of the linear algebraic equations yields the thermoelastic...
Nonlinear Elastic Analysis of FG Arcs under Thermo-Mechanical Loading
, M.Sc. Thesis Sharif University of Technology ; Fallah, Famida (Supervisor)
Abstract
Arcs and rings are used extensively in structures such as submarines and bridges due to their particular geometry. On the other hand, in multi-part rocket, due to the high temperature gradients, they form the fastening rings of functional materials (FGM). Considering the importance of this structural element, in this thesis, linear and nonlinear behavior (including bending and post-buckling) of rings made of functionally graded materials under different types of thermo-mechanical loading has been investigated. First, the governing equations are derived from the principle of minimum potential energy, based on the two theorems of Donnell and Love. Donnell's theory equations are solved...
Buckling Analysis of FG and Multilayered Cylindrical Shells Based on Third-Order Shear Deformation Theory
, M.Sc. Thesis Sharif University of Technology ; Fallah Ragabzadeh, Famida (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
In this study, based on Donnel’s shell theory and the theory of third-order shear deformation, and taking into consideration von Karman non-linearity terms, the analysis of buckling of functionally graded (FG) and multi-layered cylindrical shell with transversely isotropic layers, subjected to different loadings, was done. Along this line, first using the principle of minimum total potential energy, and based on the Donnel’s shell theory and the theory of third-order shear deformation, five couple equilibrium equations for cylindrical shell were produced. Next these five coupled equilibrium equations were reduced to three uncoupled equilibrium equation which are, in terms of transverse...
Free vibration of bi-material cylindrical shells
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 230, Issue 15 , 2016 , Pages 2637-2649 ; 09544062 (ISSN) ; Foumani, M. S ; Navazi, H. M ; Sharif University of Technology
SAGE Publications Ltd
2016
Abstract
Based on the Sanders thin shell theory, this paper presents an exact solution for the vibration of circular cylindrical shell made of two different materials. The shell is sub-divided into two segments and the state-space technique is employed to derive the homogenous differential equations. Then continuity conditions are applied where the material of the cylindrical shell changes. Shells with various combinations of end boundary conditions are analyzed by the proposed method. Finally, solving different examples, the effect of geometric parameters as well as BCs on the vibration of the bi-material shell is studied
Energy harvesting via shallow cylindrical and spherical piezoelectric panels using higher order shear deformation theory
, Article Composite Structures ; Volume 147 , 2016 , Pages 155-167 ; 02638223 (ISSN) ; Rahnama, F ; Askari Farsangi, M. A ; Sharif University of Technology
Elsevier Ltd
Abstract
In this article an analytical solution is presented for power output from a piezoelectric shallow shell energy harvester using higher order shear deformation theory (HSDT). The energy harvester is made of an elastic substrate layer coupled with one or two surface bonded piezoelectric layers. Mechanical equations of motion with Gauss's equation are derived on the basis of HSDT and solved simultaneously for simply-supported mechanical boundary conditions. The electromechanical frequency response functions that relate the power output and circuit load resistance are identified from the exact solutions. Using Rayleigh damping the influence of structural damping is taken into account. Also...
Buckling and vibration analysis of a pressurized CNT reinforced functionally graded truncated conical shell under an axial compression using HDQ method
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 303 , 2016 , Pages 75-100 ; 00457825 (ISSN) ; Asadi, H ; Wang, Q ; Sharif University of Technology
Elsevier
2016
Abstract
The present research deals with bifurcation and vibration responses of a composite truncated conical shell with embedded single-walled carbon nanotubes (SWCNTs) subjected to an external pressure and axial compression simultaneously. The distribution of reinforcements through the thickness of the shell is assumed to be either uniform or functionally graded. The equations of motion are established using Green-Lagrange type nonlinear kinematics within the framework of Novozhilov nonlinear shell theory. Linear membrane prebuckling analysis is conducted to extract the prebuckling deformations. The stability equations are derived by applying the adjacent equilibrium criterion to the prebuckling...
Computationally efficient model for flow-induced instability of CNT reinforced functionally graded truncated conical curved panels subjected to axial compression
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 318 , 2017 , Pages 957-980 ; 00457825 (ISSN) ; Asadi, H ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
As a first endeavor, the aeroelastic responses of functionally graded carbon nanotube reinforced composite (FG-CNTRC) truncated conical curved panels subjected to aerodynamic load and axial compression are investigated. The nonlinear dynamic equations of FG-CNTRC conical curved panels are derived according to Green's strains and the Novozhilov nonlinear shell theory. The aerodynamic load is estimated in accordance with the quasi-steady Krumhaar's modified supersonic piston theory by taking into account the effect of the panel curvature. Matrix transform method along with the harmonic differential quadrature method (HDQM) are employed to solve the nonlinear equations of motion of the FG-CNTRC...
Sloshing effects on supersonic flutter characteristics of a circular cylindrical shell partially filled with liquid
, Article International Journal for Numerical Methods in Engineering ; 2018 ; 00295981 (ISSN) ; Ovesy, H. R ; Dehghani Firouz Abadi, R ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
This paper aims to revisit the effect of sloshing on the flutter characteristics of a partially liquid-filled cylinder. A computational fluid-structure interaction model within the framework of the finite element method is developed to capture fluid-structure interactions arising from the sloshing of the internal fluid and the flexibility of its containing structure exposed to an external supersonic airflow. The internal liquid sloshing is represented by a more sophisticated model, referred to as the liquid sloshing model, and the shell structure is modeled by Sanders' shell theory. The aerodynamic pressure loading is approximated by the first-order piston theory. The initial geometric...
Sloshing effects on supersonic flutter characteristics of a circular cylindrical shell partially filled with liquid
, Article International Journal for Numerical Methods in Engineering ; Volume 117, Issue 8 , 2019 , Pages 901-925 ; 00295981 (ISSN) ; Ovesy, H. R ; Firouz Abadi, R. D ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
This paper aims to revisit the effect of sloshing on the flutter characteristics of a partially liquid-filled cylinder. A computational fluid-structure interaction model within the framework of the finite element method is developed to capture fluid-structure interactions arising from the sloshing of the internal fluid and the flexibility of its containing structure exposed to an external supersonic airflow. The internal liquid sloshing is represented by a more sophisticated model, referred to as the liquid sloshing model, and the shell structure is modeled by Sanders' shell theory. The aerodynamic pressure loading is approximated by the first-order piston theory. The initial geometric...
Closed-form solution for free vibration of variable-thickness cylindrical shells rotating with a constant angular velocity
, Article Thin-Walled Structures ; Volume 166 , 2021 ; 02638231 (ISSN) ; Fallah, F ; Ahmadian, M. T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Based on the classical Donnell's and Love's shell theories, free vibration behavior of variable-thickness thin cylindrical shells rotating with a constant angular velocity is analyzed. The equations of motion and corresponding boundary conditions of rotating homogenous cylindrical shells with axisymmetric variation of thickness are derived using Hamilton's principle. This formulation includes effects of initial hoop tension due to the centrifugal force as well as Coriolis and centrifugal accelerations. Considering the variation of stiffness coefficients in axial direction, the classical Love's theory results in a coupled system of two second-order and one fourth-order partial differential...
Free vibration analysis of multilayered composite cylinder consisting fibers with variable volume fraction
, Article Composite Structures ; Volume 94, Issue 3 , 2012 , Pages 931-944 ; 02638223 (ISSN) ; Hashemi, M ; Sharif University of Technology
Abstract
In this paper, free vibration of a fiber reinforced composite cylinder in which volume fraction of its fibers vary longitudinally, is studied using a semi-analytical method. The distribution of volume fraction of fiber in base matrix is based on power law model. A micromechanical model is employed to represent its mechanical properties including elastic and physical properties of this composite cylinder. In addition, kinematically the first order shear deformation shell theory is employed for strain field. Then, weak form formulation and spatial approximations of variables are utilized to discretize the equations of motion. Different problems are solved in which primarily the validity of the...
Buckling analysis of multilayered functionally graded composite cylindrical shells
, Article Applied Mechanics and Materials ; Volume 108 , 2012 , Pages 74-79 ; 16609336 (ISSN) ; 9783037852729 (ISBN) ; Hashemi, M ; Sharif University of Technology
Abstract
In this paper, the buckling analysis of a multilayered composite cylindrical shell which volume fraction of its fiber varies according to power law in longitudinal direction, due to applied compressive axial load is studied. Rule of mixture model and reverse of that are employed to represent elastic properties of this fiber reinforced functionally graded composite. Strain displacement relations employed are based on Reissner-Naghdi-Berry's shell theory. The displacement finite element model of the equilibrium equations is derived by employing weak form formulation. The Lagrangian shape function for in-plane displacements and Hermitian shape function for displacement in normal direction to...