The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Majid Ghadiri - One of the best experts on this subject based on the ideXlab platform.
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thermo mechanical vibration of orthotropic Cantilever and Propped Cantilever nanoplate using generalized differential quadrature method
2017Co-Authors: Majid Ghadiri, Navvab Shafiei, Hossein AlaviAbstract:ABSTRACTIn this article, the vibration frequency of an orthotropic nanoplate under the effect of temperature change is investigated. Using nonlocal elasticity theory, governing equations are derived. Based on the generalized differential quadrature method for Cantilever and Propped Cantilever boundary conditions, the frequencies of orthotropic nanoplates are considered and the obtained results are compared with valid reported results in the literature. The effects of temperature variation, small scale, different boundary conditions, aspect ratio, and length on natural nondimensional frequencies are studied. The present analysis is applicable for the design of rotating and nonrotating nano-devices that make use of thermo-mechanical vibration characteristics of nanoplates.
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nonlinear bending vibration of a rotating nanobeam based on nonlocal eringen s theory using differential quadrature method
2016Co-Authors: Majid Ghadiri, Navvab ShafieiAbstract:This study investigates the small scale effect on the nonlinear bending vibration of a rotating Cantilever and Propped Cantilever nanobeam. The nanobeam is modeled as an Euler---Bernoulli beam theory with von Karman geometric nonlinearity. The axial forces are also included in the model as the true spatial variation due to the rotation. Hamilton's principle is used to derive the governing equation and boundary conditions for the Euler---Bernoulli beam based on Eringen's nonlocal elasticity theory. The differential quadrature method as an efficient and accurate numerical tool in conjunction with a direct iterative method is adopted to obtain the nonlinear vibration frequencies of nanobeam. The effect of nonlocal small---scale, angular speed, hub radius and nonlinear amplitude of rotary nanobeam is discussed.
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comparison of modeling of the rotating tapered axially functionally graded timoshenko and euler bernoulli microbeams
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract The target of this paper is to present an exhaustive study on the small scale effect on vibrational behavior of a rotary tapered axially functionally graded (AFG) microbeam on the basis of Timoshenko and Euler–Bernoulli beam and modified couple stress theories. The variation of the material properties and cross section along the longitudinal direction of the microbeam are taken into consideration as a linear function. Hamilton's principle is used to derive the equations for Cantilever and Propped Cantilever boundary conditions and the generalized differential quadrature method (GDQM) is employed to solve the equations. By parametric study, the effects of small-scale parameter, rates of cross section change of the microbeam and angular velocity on the fundamental and second frequencies of the microbeam are studied. Also, comparison between the frequencies of Timoshenko and Euler–Bernoulli microbeams are presented. The results can be used in many applications such as micro-robots and biomedical microsystems.
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vibration behavior of a rotating non uniform fg microbeam based on the modified couple stress theory and gdqem
2016Co-Authors: Navvab Shafiei, Alireza Mousavi, Majid GhadiriAbstract:Abstract In this paper, for the first time, the size dependent vibration behavior of a rotating non-uniform functionally graded (FG) Timoshenko and Euler–Bernoulli microbeam based on the modified couple stress theory is presented. Also, the impact of the shear deformation on natural frequencies of the microbeam considering different values of the material length scale parameter, the angular velocity and the rate of cross section change is investigated. The mechanical and physical properties of the FG microbeam are varying along the thickness according to a power law equation. To determine governing equations, Hamilton’s principle and a generalized differential quadrature element method (GDQEM) are applied. The natural frequencies of the microbeam for Cantilever and Propped Cantilever boundary conditions are calculated. The accuracy and validity of the results are shown by several numerical examples. The influences of some parameters such as the small scale, the rate of cross section change, the angular velocity and the gradient index of the FG material on the first two natural frequencies, are plotted in several diagrams and are shown in tables. The results of this study can be used in designing and optimizing elastic and rotary type micro-electro-mechanical systems (MEMS) like micro-motors and micro-robots included rotating parts.
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on size dependent vibration of rotary axially functionally graded microbeam
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract Study of the mechanical properties of axially functionally graded (AFG) microbeams is a challenging work due to the varying mechanical properties of these microbeams along the axis. In the present study, the transverse vibration of a rotary tapered AFG Euler–Bernoulli microbeam is studied based on the modified couple stress theory by considering the axial forces which are due to the rotation, in the form of true spatial variation. The governing equations and boundary conditions are derived according to the Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature element method (GDQEM). The effects of the small-scale parameter, length and width of the beam, rate of cross-section change and nondimensional angular velocity on the vibration behavior of the non-uniform microbeam are studied for Cantilever and Propped Cantilever boundary conditions. The vibrational behavior of AFG microbeam is also compared with pure metal and pure ceramic. The results are useful in designation of micromachines such as micromotors and micro-rotors.
Navvab Shafiei - One of the best experts on this subject based on the ideXlab platform.
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thermo mechanical vibration of orthotropic Cantilever and Propped Cantilever nanoplate using generalized differential quadrature method
2017Co-Authors: Majid Ghadiri, Navvab Shafiei, Hossein AlaviAbstract:ABSTRACTIn this article, the vibration frequency of an orthotropic nanoplate under the effect of temperature change is investigated. Using nonlocal elasticity theory, governing equations are derived. Based on the generalized differential quadrature method for Cantilever and Propped Cantilever boundary conditions, the frequencies of orthotropic nanoplates are considered and the obtained results are compared with valid reported results in the literature. The effects of temperature variation, small scale, different boundary conditions, aspect ratio, and length on natural nondimensional frequencies are studied. The present analysis is applicable for the design of rotating and nonrotating nano-devices that make use of thermo-mechanical vibration characteristics of nanoplates.
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nonlinear bending vibration of a rotating nanobeam based on nonlocal eringen s theory using differential quadrature method
2016Co-Authors: Majid Ghadiri, Navvab ShafieiAbstract:This study investigates the small scale effect on the nonlinear bending vibration of a rotating Cantilever and Propped Cantilever nanobeam. The nanobeam is modeled as an Euler---Bernoulli beam theory with von Karman geometric nonlinearity. The axial forces are also included in the model as the true spatial variation due to the rotation. Hamilton's principle is used to derive the governing equation and boundary conditions for the Euler---Bernoulli beam based on Eringen's nonlocal elasticity theory. The differential quadrature method as an efficient and accurate numerical tool in conjunction with a direct iterative method is adopted to obtain the nonlinear vibration frequencies of nanobeam. The effect of nonlocal small---scale, angular speed, hub radius and nonlinear amplitude of rotary nanobeam is discussed.
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comparison of modeling of the rotating tapered axially functionally graded timoshenko and euler bernoulli microbeams
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract The target of this paper is to present an exhaustive study on the small scale effect on vibrational behavior of a rotary tapered axially functionally graded (AFG) microbeam on the basis of Timoshenko and Euler–Bernoulli beam and modified couple stress theories. The variation of the material properties and cross section along the longitudinal direction of the microbeam are taken into consideration as a linear function. Hamilton's principle is used to derive the equations for Cantilever and Propped Cantilever boundary conditions and the generalized differential quadrature method (GDQM) is employed to solve the equations. By parametric study, the effects of small-scale parameter, rates of cross section change of the microbeam and angular velocity on the fundamental and second frequencies of the microbeam are studied. Also, comparison between the frequencies of Timoshenko and Euler–Bernoulli microbeams are presented. The results can be used in many applications such as micro-robots and biomedical microsystems.
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vibration behavior of a rotating non uniform fg microbeam based on the modified couple stress theory and gdqem
2016Co-Authors: Navvab Shafiei, Alireza Mousavi, Majid GhadiriAbstract:Abstract In this paper, for the first time, the size dependent vibration behavior of a rotating non-uniform functionally graded (FG) Timoshenko and Euler–Bernoulli microbeam based on the modified couple stress theory is presented. Also, the impact of the shear deformation on natural frequencies of the microbeam considering different values of the material length scale parameter, the angular velocity and the rate of cross section change is investigated. The mechanical and physical properties of the FG microbeam are varying along the thickness according to a power law equation. To determine governing equations, Hamilton’s principle and a generalized differential quadrature element method (GDQEM) are applied. The natural frequencies of the microbeam for Cantilever and Propped Cantilever boundary conditions are calculated. The accuracy and validity of the results are shown by several numerical examples. The influences of some parameters such as the small scale, the rate of cross section change, the angular velocity and the gradient index of the FG material on the first two natural frequencies, are plotted in several diagrams and are shown in tables. The results of this study can be used in designing and optimizing elastic and rotary type micro-electro-mechanical systems (MEMS) like micro-motors and micro-robots included rotating parts.
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on size dependent vibration of rotary axially functionally graded microbeam
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract Study of the mechanical properties of axially functionally graded (AFG) microbeams is a challenging work due to the varying mechanical properties of these microbeams along the axis. In the present study, the transverse vibration of a rotary tapered AFG Euler–Bernoulli microbeam is studied based on the modified couple stress theory by considering the axial forces which are due to the rotation, in the form of true spatial variation. The governing equations and boundary conditions are derived according to the Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature element method (GDQEM). The effects of the small-scale parameter, length and width of the beam, rate of cross-section change and nondimensional angular velocity on the vibration behavior of the non-uniform microbeam are studied for Cantilever and Propped Cantilever boundary conditions. The vibrational behavior of AFG microbeam is also compared with pure metal and pure ceramic. The results are useful in designation of micromachines such as micromotors and micro-rotors.
M A Bradford - One of the best experts on this subject based on the ideXlab platform.
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analytical solutions for the time dependent behaviour of composite beams with partial interaction
2006Co-Authors: Gianluca Ranzi, M A BradfordAbstract:Abstract This paper presents a generic modelling for the time-dependent analysis of composite steel–concrete beams with partial shear interaction that occurs due to the deformation of the shear connection. The time effects considered in this modelling are those that arise from shrinkage and creep deformations of the concrete slab, and these effects are modelled using algebraic representations such as those of the age-adjusted effective modulus method (AEMM) and the mean stress method (MS), which are viscoelastic models for concrete deformation that can be stated algebraically. The generic model lends itself to closed form solutions for the analysis of composite beams subjected to a generic applied loading under a variety of end conditions. In this paper, the generic model is applied for the time-dependent analysis of composite beams that are simply supported and encastre, and to a Propped Cantilever, that are subjected to uniformly distributed loading and shrinkage deformations. Various representations of the structural behaviour of these beams are given in closed form which can also be used to benchmark available modelling techniques, i.e. finite element and finite difference formulations, which require a spatial discretisation to be specified as well as the time discretisation to perform a time analysis.
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Analysis of composite beams with partial shear interaction using available modelling techniques: A comparative study
2006Co-Authors: G. Ranzi, F. Gara, G. Leoni, M A BradfordAbstract:This paper presents a comparison of available numerical structural analysis formulations for composite beams with partial shear interaction, which include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model, and these formulations are briefly presented. The first two of these formulations lead to a numerical solution that requires a spatial discretisation to be implemented, while the direct stiffness method does not require this discretisation. Using the solution of the exact analytical model as a benchmark reference, the accuracy of the three numerical techniques is tested for the cases of a simply supported beam and a Propped Cantilever, and a qualitative comparison is carried out to highlight the adequacy and characteristics of these numerical formulations. For the two structural systems considered, the minimum spatial discretisations that need to be adopted to keep the error within an acceptable tolerance are provided for each of the formulations. (c) 2006 Elsevier Ltd. All rights reserved
Ömer Civalek - One of the best experts on this subject based on the ideXlab platform.
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on the analysis of microbeams
2017Co-Authors: Cigdem Demir, Ömer CivalekAbstract:Abstract The most widely used theory in the analysis of nanostructures is Eringen's nonlocal elasticity theory. But many researchers have mentioned that this theory has a paradox for the Cantilever boundary condition. In order to overcome this paradox, different methods of mathematical complications have been applied. By adding additional parameters to Eringen's nonlocal elasticity theory, enhanced Eringen differential model was developed as an alternative solution method without the necessity of these complications. In this paper, bending of nano/micro beams under the concentrated and distributed loads has been investigated by using Euler Bernoulli beam theory via the enhanced Eringen differential model. Singularity function method is used to calculate the deflection of concentrated and distributed loaded beam. Various types of boundary conditions are considered for the beam such as Cantilever, clamped, Propped Cantilever and simply supported. In each case of boundary conditions, closed form solutions for the bending of the beam are presented for various loading locations. Deflection, bending moment and shear force are presented comparatively for variable loadings in figures and tables.
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analysis of micro sized beams for various boundary conditions based on the strain gradient elasticity theory
2012Co-Authors: Bekir Akgoz, Ömer CivalekAbstract:Bending analysis of micro-sized beams based on the Bernoulli-Euler beam theory is presented within the modified strain gradient elasticity and modified couple stress theories. The governing equations and the related boundary conditions are derived from the variational principles. These equations are solved analytically for deflection, bending, and rotation responses of micro-sized beams. Propped Cantilever, both ends clamped, both ends simply supported, and Cantilever cases are taken into consideration as boundary conditions. The influence of size effect and additional material parameters on the static response of micro-sized beams in bending is examined. The effect of Poisson’s ratio is also investigated in detail. It is concluded from the results that the bending values obtained by these higher-order elasticity theories have a significant difference with those calculated by the classical elasticity theory.
Mohammad Kazemi - One of the best experts on this subject based on the ideXlab platform.
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comparison of modeling of the rotating tapered axially functionally graded timoshenko and euler bernoulli microbeams
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract The target of this paper is to present an exhaustive study on the small scale effect on vibrational behavior of a rotary tapered axially functionally graded (AFG) microbeam on the basis of Timoshenko and Euler–Bernoulli beam and modified couple stress theories. The variation of the material properties and cross section along the longitudinal direction of the microbeam are taken into consideration as a linear function. Hamilton's principle is used to derive the equations for Cantilever and Propped Cantilever boundary conditions and the generalized differential quadrature method (GDQM) is employed to solve the equations. By parametric study, the effects of small-scale parameter, rates of cross section change of the microbeam and angular velocity on the fundamental and second frequencies of the microbeam are studied. Also, comparison between the frequencies of Timoshenko and Euler–Bernoulli microbeams are presented. The results can be used in many applications such as micro-robots and biomedical microsystems.
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on size dependent vibration of rotary axially functionally graded microbeam
2016Co-Authors: Navvab Shafiei, Mohammad Kazemi, Majid GhadiriAbstract:Abstract Study of the mechanical properties of axially functionally graded (AFG) microbeams is a challenging work due to the varying mechanical properties of these microbeams along the axis. In the present study, the transverse vibration of a rotary tapered AFG Euler–Bernoulli microbeam is studied based on the modified couple stress theory by considering the axial forces which are due to the rotation, in the form of true spatial variation. The governing equations and boundary conditions are derived according to the Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature element method (GDQEM). The effects of the small-scale parameter, length and width of the beam, rate of cross-section change and nondimensional angular velocity on the vibration behavior of the non-uniform microbeam are studied for Cantilever and Propped Cantilever boundary conditions. The vibrational behavior of AFG microbeam is also compared with pure metal and pure ceramic. The results are useful in designation of micromachines such as micromotors and micro-rotors.
