Loading...
Search for:
von-karman
0.006 seconds
Total 28 records
Dynamic instability responses of the substructure living biological cells in the cytoplasm environment using stress-strain size-dependent theory
, Article Journal of Biomolecular Structure and Dynamics ; 17 April , 2020 ; Jamali, M ; Habibi, M ; Sadeghi, S ; Jung, D. W ; Nabipour, N ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Over the last few years, some novel researches in the field of medical science made a tendency to have a therapy without any complications or side-effects of the disease with the aid of prognosis about the behaviors of the substructure living biological cell. Regarding this issue, nonlinear frequency characteristics of substructure living biological cell in axons with attention to different size effect parameters based on generalized differential quadrature method is presented. Supporting the effects of surrounding cytoplasm and MAP Tau proteins are considered as nonlinear elastic foundation. The Substructure living biological cell are modeled as a moderately thick curved cylindrical...
Analytical Solution to Bending of Shape Memory Polymer Beams
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Baghani, Mostafa (Co-Advisor)
Abstract
Shape Memory Polymers (SMPs) are a class of smart materials capable of remembering multiple shapes, and transitioning between them in response to an external stimulus such as thermal or magnetic induction. SMPs have attracted significant attention of both industrial and academic researchers due to their useful and attractive functionality. This thesis aims to analytically develop Euler-Bernoulli, Timoshenko and von Karman theories for beam bending in small strain regime considering SMP constitutive equations. To properly introduce analytical solution for the problem of beam bending, the constitutive model proposed by Baghani et al. (2012) has been used. For this purpose, three dimensional...
Numerical Investigation of Vortex Shedding Control Behind a Cylinder with Swinging Thin Plates
, M.Sc. Thesis Sharif University of Technology ; Javadi, Khodayar (Supervisor) ; Tayyebi Rahni, Mohammad (Co-Advisor)
Abstract
Von-Karman vortex shedding is a transient aerodynamic instability which occurs in laminar flows over a bluff body in a certain condition. When this phenomenon occurs, vortices take form on upper and lower parts of the bluff body and begin to shed into an oscillatory manner affecting a significant part of the flow domain. This research focuses on Karman vortex shedding control by using two thin oscillating splitter plates. Length ratio of plates to cylinder diameter is 1 (L⁄D=1) and plates are attached at ±55 degrees (trigonometric angle). Plates are forced to oscillate at different ratios of natural vortex shedding frequencies (0.75, 1, 1.25, 1.5 and 2) for diffenet amplitudes. Simulations...
Non-linear thermo-mechanical cylindrical bending of functionally graded plates
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 222, Issue 3 , 2008 , Pages 305-318 ; 09544062 (ISSN) ; Nosier, A ; Sharif University of Technology
2008
Abstract
Based on the first-order non-linear von Karman theory, cylindrical bending of functionally graded (FG) plates subjected to mechanical, thermal, and combined thermo-mechanical loadings are investigated. Analytical solutions are obtained for an FG plate with various clamped and simply-supported boundary conditions. The closed form solutions obtained are very simple to be used in design purposes. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. The effects of non-linearity, material property, and boundary conditions on various response quantities are studied and...
On the nonlinear dynamics of a multi-scale hybrid nanocomposite disk
, Article Engineering with Computers ; 2020 ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer
2020
Abstract
This is the first research on the nonlinear frequency analysis of a multi-scale hybrid nanocomposite (MHC) disk (MHCD) resting on an elastic foundation subjected to nonlinear temperature gradient and mechanical loading is investigated. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. We present a modified Halpin–Tsai model to predict the effective properties of the MHCD. The displacement–strain of nonlinear vibration of multi-scale laminated disk via third-order shear deformation theory (TSDT) and using Von Karman nonlinear shell theory is obtained. Hamilton’s principle is employed to establish the governing...
Nonlinear Forced Vibrations of Thin Circular and Elliptical Functionally Graded Plates
, M.Sc. Thesis Sharif University of Technology ; Nosier, Asghar (Supervisor)
Abstract
Nonlinear forced vibrations of thin functionally graded circular and elliptical plates under classical boundary conditions are investigated based on the classical plate theory. The von Kármán strain-displacement relations is employed to include geometrical nonlinearity caused by large transverse displacements of the plate thickness order, and modal expansion in polar and elliptical coordinate along with the perturbation method of multiple scale is used to solve the governing equations. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. Transverse forcing is supposed to be harmonic with angular...
Nonlinear Aeroelastic Analysis of Composite Wing at a Hale Flight Vehicle
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firouz-Abadi, Roholla (Supervisor)
Abstract
The purpose of this study is aeroelastic stability analysis and nonlinear aeroelastic vibration of composite wing with nonlinear 1D beam model. Wing’s structure modelled as thin-walled composite single box beam in linear and nonlinear conditions. Thin-walled composite box beam developed by classical lamination theory and structural nonlinearity is von karman strain. Unsteady aerodynamic of wing modelled with modified strip theory. Aeroelastic equations of wing obtained from modal expansion (assumed mode) and Hamilton’s Principle. In order to stability analysis of wing, the linear aeroelastic equations in state space must be calculated and so with eigenvalue analysis instability speed will be...
Nonlinear Vibrations of a Circular Plate Using Perturbation and Experimental Methods
, M.Sc. Thesis Sharif University of Technology ; Navazi, Hossein Mohammad (Supervisor)
Abstract
In this thesis, the nonlinear vibrations of the circular plate is examined using multiple scale methods and experimental tests. At first step, the nonlinear equations governing the problem are written using von Karman's assumption. In the next step, to solve nonlinear equations and calculate natural frequency, the problem is solved using multiple scale method and frequency charts are extracted as a function of the amplitude of vibration. . The design of the setup has been done in such a way that it is possible to simulate the boundary conditions. In the first phase, experimental tests was performed on a 0.3 mm thick aluminum sheet, which did not produce the desired results due to the...
Dynamic Response Analysis of a Three-Layered Circular Plate with Magnetorheological Fluid Core Under Low Velocity Impact Loading
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
Various public transportation types, e.g., Trains, Buses, and Airplanes, are susceptible to damages made by the impacts of the external objects, which are typically classified as low to medium velocity impacts. This problem reveals the significance of investigating the effects of impact on thin-walled structures, which are the main components of these vehicles' bodies. Owing to the controllable rheological properties of the Magnetorheological fluid with respect to the magnetic field, it can be utilized to control the structure exposed to impact adaptively and minimize the damages. Due to this purpose, sandwich structures such as sandwich beams and plates, thanks to their extended response...
Elastic collapse of thin long cylindrical shells under external pressure
, Article Thin-Walled Structures ; Volume 124 , 2018 , Pages 81-87 ; 02638231 (ISSN) ; Fallah, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This paper investigates local elastic buckling of thin long cylindrical shells under external pressure. Based on Donnell's and Sanders’ theories of thin shells and von Karman nonlinearity assumptions, the potential energy is derived. The buckling load and curves of the static equilibrium path are obtained using the Ritz method. The results are validated with the existing ones in the literature. Furthermore, the case where the pressure is perpendicular to the deformed state is compared with a dead loading. It is demonstrated that the former yields a lower critical pressure in both shell theories. © 2017 Elsevier Ltd
On the nonlinear dynamics of a multi-scale hybrid nanocomposite disk
, Article Engineering with Computers ; Volume 37, Issue 3 , 2021 , Pages 2369-2388 ; 01770667 (ISSN) ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
This is the first research on the nonlinear frequency analysis of a multi-scale hybrid nanocomposite (MHC) disk (MHCD) resting on an elastic foundation subjected to nonlinear temperature gradient and mechanical loading is investigated. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. We present a modified Halpin–Tsai model to predict the effective properties of the MHCD. The displacement–strain of nonlinear vibration of multi-scale laminated disk via third-order shear deformation theory (TSDT) and using Von Karman nonlinear shell theory is obtained. Hamilton’s principle is employed to establish the governing...
Nonlinear responses of unbalanced flexible rotating shaft passing through critical speeds
, Article Meccanica ; 2021 ; 00256455 (ISSN) ; Rokn Abadi, M ; Firouz Abadi, R.D ; Mehralian, F ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
This work studies the nonlinear oscillations of an elastic rotating shaft with acceleration to pass through the critical speeds. A mathematical model incorporating the Von-Karman higher-order deformations in bending is developed and analyzed to investigate the nonlinear dynamics of rotors. A flexible shaft on flexible bearings with springs and dampers is considered as rotor system for the present work. The shaft is modeled as a beam with a circular cross-section and the Euler Bernoulli beam theory is applied. The kinetic and strain energies of the rotor system are derived and Lagrange method is then applied to obtain the coupled nonlinear differential equations of motion for 6° of freedom....
Nonlinear responses of unbalanced flexible rotating shaft passing through critical speeds
, Article Meccanica ; Volume 57, Issue 1 , 2022 , Pages 193-212 ; 00256455 (ISSN) ; Rokn Abadi, M ; Firouz Abadi, R. D ; Mehralian, F ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
This work studies the nonlinear oscillations of an elastic rotating shaft with acceleration to pass through the critical speeds. A mathematical model incorporating the Von-Karman higher-order deformations in bending is developed and analyzed to investigate the nonlinear dynamics of rotors. A flexible shaft on flexible bearings with springs and dampers is considered as rotor system for the present work. The shaft is modeled as a beam with a circular cross-section and the Euler Bernoulli beam theory is applied. The kinetic and strain energies of the rotor system are derived and Lagrange method is then applied to obtain the coupled nonlinear differential equations of motion for 6° of freedom....
Developing the Nonlinear Model of Single-Cell Thin-Walled Closed-Section Composite Beams
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firoozabadi, Rouhollah (Supervisor)
Abstract
The purpose of this study is to develop the reduced order nonlinear modeling of single cell closed section thin walled composite beams. In this way, global behavior of one dimensional beam under axial load, bending and torsional moment is produced. This model is based on the classical lamination theory, and the nonlinear model is developedby usingthe von-karman strains. In this process the effects of material anisotropy and axial warping are considered. Numerical results are obtained for thin-walledcomposites box beams, addressing the effects of fiber angle and laminate stacking sequence. The nonlinear model is compared with theoretical results of homogeneous beams and the natural...
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...
Large amplitude thermo-mechanical vibration analysis of asymmetrically laminated composite beams
, Article Key Engineering Materials, 22 March 2011 through 24 March 2011, Kuala Lumpur ; Volume 471-472 , 2011 , Pages 745-750 ; 10139826 (ISSN) ; 9783037850596 (ISBN) ; Alavijeh, H. S ; Pasharavesh, A ; Aghdam, M. M ; Sharif University of Technology
2011
Abstract
In this paper, simple analytical expression is presented for large amplitude thermomechanical free vibration analysis of asymmetrically laminated composite beams. Euler-Bernoulli assumptions together with Von Karman's strain-displacement relation are employed to derive the nonlinear governing partial differential equation (PDE) of motion. He's variational method is employed to obtain a simple and efficient approximate closed form solution of the nonlinear governing equation. Comparison between results of the present work and those available in literature shows the accuracy of presented technique. Some new results for the nonlinear natural frequencies of the laminated beams such as the effect...
Non-linear vibration analysis of laminated composite plates resting on non-linear elastic foundations
, Article Journal of the Franklin Institute ; Volume 348, Issue 2 , March , 2011 , Pages 353-368 ; 00160032 (ISSN) ; Fesanghary, M ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
In this study, the homotopy analysis method (HAM) is used to obtain an approximate analytical solution for geometrically non-linear vibrations of thin laminated composite plates resting on non-linear elastic foundations. Geometric non-linearity is considered using von Karman's straindisplacement relations. Then, the effects of the initial deflection, ply properties, aspect ratio of the plate and foundation parameters on the non-linear free vibration is studied. Comparison between the obtained results and those available in the literature demonstrates the potential of HAM for the analysis of such vibration problems, whose governing differential equations include the quadratic and cubic...
Dynamic response of geometrically nonlinear, elastic rectangular plates under a moving mass loading by inclusion of all inertial components
, Article Journal of Sound and Vibration ; Volume 394 , 2017 , Pages 497-514 ; 0022460X (ISSN) ; Enshaeian, A ; Nikkhoo, A ; Sharif University of Technology
Academic Press
2017
Abstract
Dynamic deformations of beams and plates under moving objects have extensively been studied in the past. In this work, the dynamic response of geometrically nonlinear rectangular elastic plates subjected to moving mass loading is numerically investigated. A rectangular von Karman plate with various boundary conditions is modeled using specifically developed geometrically nonlinear plate elements. In the available finite element (FE) codes the only way to distinguish between moving masses from moving loads is to model the moving mass as a separate entity. However, these procedures still do not guarantee the inclusion of all inertial effects associated with the moving mass. In a prepared...
Decoupled stability equation for buckling analysis of FG and multilayered cylindrical shells based on the first-order shear deformation theory
, Article Composites Part B: Engineering ; Volume 154 , 2018 , Pages 225-241 ; 13598368 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Based on the first-order shear deformation and Donnell's shell theory with von Karman non-linearity, one decoupled stability equation for buckling analysis of functionally graded (FG) and multilayered cylindrical shells with transversely isotropic layers subjected to various cases of combined thermo-mechanical loadings is developed. To this end, the equilibrium equations are uncoupled in terms of the transverse deflection, the force function and a new potential function. Using the adjacent equilibrium method, one decoupled stability equation which is an eighth-order differential equation in terms of transverse deflection is obtained and conveniently solved to present analytical expressions...
Nonlinear dynamic analysis of SWNTs conveying fluid using nonlocal continuum theory
, Article Structural Engineering and Mechanics ; Volume 66, Issue 5 , 10 June , 2018 , Pages 621-629 ; 12254568 (ISSN) ; Mousavi, T ; Bahai, H ; Sharif University of Technology
Techno Press
2018
Abstract
By employing the nonlocal continuum field theory of Eringen and Von Karman nonlinear strains, this paper presents an analytical model for linear and nonlinear dynamics analysis of single-walled carbon nanotubes (SWNTs) conveying fluid with different boundary conditions. In the linear analysis the natural frequencies and critical flow velocities of SWNTs are computed. However, in the nonlinear analysis the effect of nonlocal parameter on nonlinear dynamics of cantilevered SWNTs conveying fluid is investigated by using bifurcation diagram, phase plane and Poincare map. Numerical results confirm existence of chaos as well as a period-doubling transition to chaos. Copyright © 2018 Techno-Press,...