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R Ansari - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear Forced Vibration analysis of fg cntrc cylindrical shells under thermal loading using a numerical strategy
    International Journal of Applied Mechanics, 2017
    Co-Authors: E Hasrati, R Ansari, Jalal Torabi
    Abstract:

    Employing an efficient numerical strategy, the nonlinear Forced Vibration analysis of composite cylindrical shells reinForced with single-walled carbon nanotubes (CNTs) is carried out. It is assume...

  • size dependent geometrically nonlinear Forced Vibration analysis of functionally graded first order shear deformable microplates
    Journal of Mechanics, 2016
    Co-Authors: R Ansari, R Gholami, A Shahabodini
    Abstract:

    In this paper, a non-classical plate model capturing the size effect is developed to study the Forced Vibration of functionally graded (FG) microplates subjected to a harmonic excitation transverse force. To this, the modified couple stress theory (MCST) is incorporated into the first-order shear deformation plate theory (FSDPT) to account for the size effect through one length scale parameter, only. Strong form of nonlinear governing equations and associated boundary conditions are obtained using Hamilton's principle. The solution process is implemented on two domains. The generalized differential quadrature (GDQ) method is first employed to discretize the governing equations on the space domain. A Galerkin-based scheme is then applied to extract a reduced set of the nonlinear equations of Duffing-type. On the second domain, through a time differentiation matrix operator, the set of ordinary differential equations are transformed into the discrete form on time domain. Eventually, a system of the parameterized nonlinear equations is acquired and solved via the pseudo-arc length continuation method. The frequency response curve of the microplate is sketched and the effects of various material and geometrical parameters on it are evaluated.

  • surface effect on the large amplitude periodic Forced Vibration of first order shear deformable rectangular nanoplates with various edge supports
    Acta Astronautica, 2016
    Co-Authors: R Ansari, R Gholami
    Abstract:

    Abstract Surface stress and surface inertia effects may play a significant role in the mechanical characteristics of nanostructures with a high surface to volume ratio. The objective of this study is to present a comprehensive study on the surface stress and surface inertia effects on the large amplitude periodic Forced Vibration of first-order shear deformable rectangular nanoplates. To this end, the Gurtin–Murdoch theory, first-order shear deformation theory (FSDT) and Hamilton׳s principle are employed to develop a non-classical continuum plate model capable of taking the surface stress and surface inertia effects and also the rotary and in-plane inertias into account. To solve numerically the geometrically nonlinear Forced Vibration of nanoplates with different boundary conditions, the generalized differential quadrature (GDQ) method, numerical Galerkin scheme, periodic time differential operators and pseudo arc-length continuation method are employed. The effects of parameters such as thickness, surface residual stress, surface elasticity, surface mass density, length-to-thickness ratio, width-to-thickness ratio and boundary conditions on the nonlinear Forced Vibration of rectangular nanoplates are fully investigated. The results demonstrate that surface effects on the nonlinear frequency response of aluminum (Al) nanoplate are more prominent in comparison with the silicon (Si) nanoplate.

  • nonlinear analysis of Forced Vibration of nonlocal third order shear deformable beam model of magneto electro thermo elastic nanobeams
    Composites Part B-engineering, 2015
    Co-Authors: R Ansari, R Gholami, E Hasrati, F Sadeghi
    Abstract:

    Abstract This paper deals with the Forced Vibration behavior of nonlocal third-order shear deformable beam model of magneto–electro–thermo elastic (METE) nanobeams based on the nonlocal elasticity theory in conjunction with the von Karman geometric nonlinearity. The METE nanobeam is assumed to be subjected to the external electric potential, magnetic potential and constant temperature rise. Based on the Hamilton principle, the nonlinear governing equations and corresponding boundary conditions are established and discretized using the generalized differential quadrature (GDQ) method. Thereafter, using a Galerkin-based numerical technique, the set of nonlinear governing equations is reduced into a time-varying set of ordinary differential equations of Duffing type. The pseudo-arc length continuum scheme is then adopted to solve the vectorized form of nonlinear parameterized equations. Finally, a comprehensive study is conducted to get an insight into the effects of different parameters such as nonlocal parameter, slenderness ratio, initial electric potential, initial external magnetic potential, temperature rise and type of boundary conditions on the natural frequency and Forced Vibration characteristics of METE nanobeams.

  • size dependent nonlinear Forced Vibration analysis of magneto electro thermo elastic timoshenko nanobeams based upon the nonlocal elasticity theory
    Composite Structures, 2015
    Co-Authors: R Ansari, R Gholami, H Rouhi
    Abstract:

    Abstract In this article, a nonlocal geometrically nonlinear beam model is developed for magneto-electro-thermo-elastic (METE) nanobeams subjected to external electric voltage, external magnetic potential and uniform temperature rise. The effects of transverse shear deformation, rotary inertia and geometric nonlinearity are taken into account through using the Timoshenko beam theory together with von Karman’s hypothesis. Also, the size-dependent nonlinear Forced Vibration behavior of METE nanobeams under different model parameters is studied based on an efficient numerical solution procedure. The governing equations and boundary conditions are obtained on the basis of Hamilton’s principle which are then discretized via the generalized differential quadrature (GDQ) method. A numerical Galerkin procedure is employed to derive the Duffing-type equations. The resulting equations are discretized on time domain using a set of time differential matrix operators that are defined based on the derivatives of a periodic base function. The pseudo arc-length continuation algorithm is finally applied to obtain the response curves of METE nanobeams with different types of end conditions. In the numerical results, the influences of temperature change, nonlocal parameter, external electric voltage and external magnetic potential on the nonlinear Forced Vibration behavior of METE nanobeams are explored. It is shown that the hardening-type response of nanobeams intensifies as the nonlocal parameter increases. In addition, the effects of external magnetic potential and electric voltage on the response curves are significant especially for simply-supported nanobeams.

R Gholami - One of the best experts on this subject based on the ideXlab platform.

  • size dependent geometrically nonlinear Forced Vibration analysis of functionally graded first order shear deformable microplates
    Journal of Mechanics, 2016
    Co-Authors: R Ansari, R Gholami, A Shahabodini
    Abstract:

    In this paper, a non-classical plate model capturing the size effect is developed to study the Forced Vibration of functionally graded (FG) microplates subjected to a harmonic excitation transverse force. To this, the modified couple stress theory (MCST) is incorporated into the first-order shear deformation plate theory (FSDPT) to account for the size effect through one length scale parameter, only. Strong form of nonlinear governing equations and associated boundary conditions are obtained using Hamilton's principle. The solution process is implemented on two domains. The generalized differential quadrature (GDQ) method is first employed to discretize the governing equations on the space domain. A Galerkin-based scheme is then applied to extract a reduced set of the nonlinear equations of Duffing-type. On the second domain, through a time differentiation matrix operator, the set of ordinary differential equations are transformed into the discrete form on time domain. Eventually, a system of the parameterized nonlinear equations is acquired and solved via the pseudo-arc length continuation method. The frequency response curve of the microplate is sketched and the effects of various material and geometrical parameters on it are evaluated.

  • surface effect on the large amplitude periodic Forced Vibration of first order shear deformable rectangular nanoplates with various edge supports
    Acta Astronautica, 2016
    Co-Authors: R Ansari, R Gholami
    Abstract:

    Abstract Surface stress and surface inertia effects may play a significant role in the mechanical characteristics of nanostructures with a high surface to volume ratio. The objective of this study is to present a comprehensive study on the surface stress and surface inertia effects on the large amplitude periodic Forced Vibration of first-order shear deformable rectangular nanoplates. To this end, the Gurtin–Murdoch theory, first-order shear deformation theory (FSDT) and Hamilton׳s principle are employed to develop a non-classical continuum plate model capable of taking the surface stress and surface inertia effects and also the rotary and in-plane inertias into account. To solve numerically the geometrically nonlinear Forced Vibration of nanoplates with different boundary conditions, the generalized differential quadrature (GDQ) method, numerical Galerkin scheme, periodic time differential operators and pseudo arc-length continuation method are employed. The effects of parameters such as thickness, surface residual stress, surface elasticity, surface mass density, length-to-thickness ratio, width-to-thickness ratio and boundary conditions on the nonlinear Forced Vibration of rectangular nanoplates are fully investigated. The results demonstrate that surface effects on the nonlinear frequency response of aluminum (Al) nanoplate are more prominent in comparison with the silicon (Si) nanoplate.

  • nonlinear analysis of Forced Vibration of nonlocal third order shear deformable beam model of magneto electro thermo elastic nanobeams
    Composites Part B-engineering, 2015
    Co-Authors: R Ansari, R Gholami, E Hasrati, F Sadeghi
    Abstract:

    Abstract This paper deals with the Forced Vibration behavior of nonlocal third-order shear deformable beam model of magneto–electro–thermo elastic (METE) nanobeams based on the nonlocal elasticity theory in conjunction with the von Karman geometric nonlinearity. The METE nanobeam is assumed to be subjected to the external electric potential, magnetic potential and constant temperature rise. Based on the Hamilton principle, the nonlinear governing equations and corresponding boundary conditions are established and discretized using the generalized differential quadrature (GDQ) method. Thereafter, using a Galerkin-based numerical technique, the set of nonlinear governing equations is reduced into a time-varying set of ordinary differential equations of Duffing type. The pseudo-arc length continuum scheme is then adopted to solve the vectorized form of nonlinear parameterized equations. Finally, a comprehensive study is conducted to get an insight into the effects of different parameters such as nonlocal parameter, slenderness ratio, initial electric potential, initial external magnetic potential, temperature rise and type of boundary conditions on the natural frequency and Forced Vibration characteristics of METE nanobeams.

  • size dependent nonlinear Forced Vibration analysis of magneto electro thermo elastic timoshenko nanobeams based upon the nonlocal elasticity theory
    Composite Structures, 2015
    Co-Authors: R Ansari, R Gholami, H Rouhi
    Abstract:

    Abstract In this article, a nonlocal geometrically nonlinear beam model is developed for magneto-electro-thermo-elastic (METE) nanobeams subjected to external electric voltage, external magnetic potential and uniform temperature rise. The effects of transverse shear deformation, rotary inertia and geometric nonlinearity are taken into account through using the Timoshenko beam theory together with von Karman’s hypothesis. Also, the size-dependent nonlinear Forced Vibration behavior of METE nanobeams under different model parameters is studied based on an efficient numerical solution procedure. The governing equations and boundary conditions are obtained on the basis of Hamilton’s principle which are then discretized via the generalized differential quadrature (GDQ) method. A numerical Galerkin procedure is employed to derive the Duffing-type equations. The resulting equations are discretized on time domain using a set of time differential matrix operators that are defined based on the derivatives of a periodic base function. The pseudo arc-length continuation algorithm is finally applied to obtain the response curves of METE nanobeams with different types of end conditions. In the numerical results, the influences of temperature change, nonlocal parameter, external electric voltage and external magnetic potential on the nonlinear Forced Vibration behavior of METE nanobeams are explored. It is shown that the hardening-type response of nanobeams intensifies as the nonlocal parameter increases. In addition, the effects of external magnetic potential and electric voltage on the response curves are significant especially for simply-supported nanobeams.

  • Forced Vibration analysis of functionally graded carbon nanotube reinForced composite plates using a numerical strategy
    Physica E-low-dimensional Systems & Nanostructures, 2015
    Co-Authors: R Ansari, Faghih M Shojaei, R Gholami, E Hasrati, A Shahabodini
    Abstract:

    Abstract In this paper, the nonlinear Forced Vibration behavior of composite plates reinForced by carbon nanotubes is investigated by a numerical approach. The reinforcement is considered to be functionally graded (FG) in the thickness direction according to a micromechanical model. The first-order shear deformation theory and von Karman-type kinematic relations are employed. The governing equations and the corresponding boundary conditions are derived with the use of Hamilton's principle. The generalized differential quadrature (GDQ) method is utilized to achieve a discretized set of nonlinear governing equations. A Galerkin-based scheme is then applied to obtain a time-varying set of ordinary differential equations of Duffing-type. Subsequently, a time periodic discretization is done and the frequency response of plates is determined via the pseudo-arc length continuation method. Selected numerical results are given for the effects of different parameters on the nonlinear Forced Vibration characteristics of uniformly distributed carbon nanotube- and FG carbon nanotube-reinForced composite plates. It is found that with the increase of CNT volume fraction, the flexural stiffness of plate increases; and hence its natural frequency gets larger. Moreover, it is observed that the distribution type of CNTs significantly affects the Vibrational behavior of plate. The results also show that when the mid-plane of plate is CNT-rich, the natural frequency takes its minimum value and the hardening-type response of plate is intensified.

F Sadeghi - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear analysis of Forced Vibration of nonlocal third order shear deformable beam model of magneto electro thermo elastic nanobeams
    Composites Part B-engineering, 2015
    Co-Authors: R Ansari, R Gholami, E Hasrati, F Sadeghi
    Abstract:

    Abstract This paper deals with the Forced Vibration behavior of nonlocal third-order shear deformable beam model of magneto–electro–thermo elastic (METE) nanobeams based on the nonlocal elasticity theory in conjunction with the von Karman geometric nonlinearity. The METE nanobeam is assumed to be subjected to the external electric potential, magnetic potential and constant temperature rise. Based on the Hamilton principle, the nonlinear governing equations and corresponding boundary conditions are established and discretized using the generalized differential quadrature (GDQ) method. Thereafter, using a Galerkin-based numerical technique, the set of nonlinear governing equations is reduced into a time-varying set of ordinary differential equations of Duffing type. The pseudo-arc length continuum scheme is then adopted to solve the vectorized form of nonlinear parameterized equations. Finally, a comprehensive study is conducted to get an insight into the effects of different parameters such as nonlocal parameter, slenderness ratio, initial electric potential, initial external magnetic potential, temperature rise and type of boundary conditions on the natural frequency and Forced Vibration characteristics of METE nanobeams.

  • nonlinear Forced Vibration analysis of functionally graded carbon nanotube reinForced composite timoshenko beams
    Composite Structures, 2014
    Co-Authors: R Ansari, V Mohammadi, Faghih M Shojaei, R Gholami, F Sadeghi
    Abstract:

    Abstract This research deals with the Forced Vibration behavior of nanocomposite beams reinForced by single-walled carbon nanotubes (SWCNTs) based on the Timoshenko beam theory along with von Karman geometric nonlinearity. For the carbon-nanotube reinForced composite (CNTRC) beams, uniform distribution (UD) and three types of functionally graded (FG) distribution patterns of SWCNT reinforcements are considered. It is assumed that the material properties of FG-CNTRC beams are graded in the thickness direction and estimated through the rule of mixture. The nonlinear governing equations and corresponding boundary conditions are derived based on the Hamilton principle and discretized by means of the generalized differential quadrature (GDQ) method. After that, a Galerkin-based numerical technique is employed to reduce the set of nonlinear governing equations into a time-varying set of ordinary differential equations of Duffing type. Since the nanobeam responds periodically to harmonic excitations, a set of periodic differential matrix operators is introduced to discretize the Duffing equations on the time domain using the derivatives of a periodic base function. The vectorized form of final nonlinear parameterized equations is then solved through the use of pseudo-arc length continuum technique. Numerical results are presented to examine the effects of different parameters such as nanotube volume fraction, slenderness ratio, dimensionless damping parameter, dimensionless transverse force, CNT distributions and boundary conditions on the natural frequencies and frequency responses of FG-CNTRC beams.

Zhigang Liu - One of the best experts on this subject based on the ideXlab platform.

  • free and Forced Vibration analysis of coupled conical cylindrical shells with arbitrary boundary conditions
    International Journal of Mechanical Sciences, 2014
    Co-Authors: Guoyong Jin, Yeping Xiong, Zhigang Liu
    Abstract:

    This paper presents a free and Forced Vibration analysis of coupled conical–cylindrical shells with arbitrary boundary conditions using a modified Fourier–Ritz method. Under the current framework, regardless of the boundary conditions, each of the displacement components of both the conical and cylindrical shells are expanded invariantly as a modified Fourier series, which is composed of a standard Fourier series and closed-form supplementary functions introduced to accelerate the convergence of the series expansion and remove all the relevant discontinuities at the boundaries and the junction between the two shell components. All the expansion coefficients are determined by using the Rayleigh–Ritz method as the generalized coordinates. By using the present method, a unified solution for the coupled conical–cylindrical shells with classical and non-classical boundary conditions can be directly derived without the need of changing either the equations of motion or the expressions of the displacements. The reliability and accuracy of the present method are validated by comparison with FEM results and those from the literature. Studies on the effects of dimensional and elastic restraint parameters on the free Vibrations are also reported. Investigation on Vibration of the conical–cylindrical–conical shell combination shows the extensive applicability of present method for more complex shell combinations. New numerical examples are also conducted to illustrate the Forced Vibration behavior of the coupled conical–cylindrical shell subjected to the excitation forces in different directions.

B P Patel - One of the best experts on this subject based on the ideXlab platform.

  • free and Forced Vibration characteristics of bimodular composite laminated circular cylindrical shells
    Composite Structures, 2015
    Co-Authors: K Khan, B P Patel, Y Nath
    Abstract:

    Abstract The free and Forced Vibration characteristics of bimodular cross-ply laminated clamped–clamped circular cylindrical shells are studied using Bert’s and a recently proposed model considering first order shear deformation theory. The free Vibration frequencies in positive and negative half cycles are found to be same for all asymmetric modes and for axisymmetric modes with even number of axial half waves, and different for axisymmetric modes with odd number of axial half waves. However, the negative half cycle amplitude is significantly greater than the positive half cycle amplitude due to the local stiffness of bimodular cylindrical shells being different for positive and negative half cycles even though the natural frequencies are same for positive and negative half cycles of asymmetric Vibrations. The relative difference of positive and negative half cycle frequencies is very less for single layer orthotropic shells, and it is significant for cross-ply shells for axisymmetric mode of Vibration. The Vibration characteristics predicted using proposed and Bert’s constitutive models are quite close except for the transverse to the fiber direction normal stress.

  • nonlinear Forced Vibration response of bimodular laminated composite plates
    Composite Structures, 2014
    Co-Authors: Arshad Hussain Khan, B P Patel
    Abstract:

    Abstract The nonlinear Forced Vibration characteristics of bimodular material laminated cross-ply composite plates subjected to periodic excitation are investigated. The analysis is carried out using Bert’s constitutive model employing first order shear deformation theory based finite element method (FEM) including von Karman geometric nonlinearity. The periodic response is obtained using shooting technique coupled with Newmark time marching, arc length and pseudo-arc length continuation algorithms. The second order differential equation of motion is solved directly without transforming to first order differential equations thereby preserving the banded nature of equations. The nonlinear periodic Vibration characteristics such as steady state response history, phase plane plots and frequency spectra are presented. A detailed parametric study is carried out to analyse the influence of bimodularity, aspect ratio, thickness ratio, excitation amplitude, support conditions and lamination scheme on the Forced Vibration response. The significant difference in the positive/negative half cycle amplitudes due to bimodularity is predicted with/without geometric nonlinearity. The through the thickness variation of fiber direction normal strain is presented to show the extent of assignment of tensile/compressive properties and restoring force due to geometric nonlinearity. Further, the unstable regions of the frequency response curves between turning points could not be traced due to the perturbations stemming from the numerical truncation in finite element discretization/solution of equations and the bimodular action resulting in deviation of solution in shooting iterations leading to convergence failure.