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      • Dynamic instability region analysis of reinforced-CNTs truncated conical shells using mixed DQ-Bolotin method

        H. Vossough,F. Ahmadi,S. Golabi 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.2

        In this paper, dynamic buckling of truncated conical shell made of carbon nanotubes (CNTs) composite is studied. In aerospace industries, this category of structures is utilized extensively due to wide range of engineering applications. To calculate the effective material properties of the nanocomposite, The Mori-Tanaka model is applied. Also, the motion equations are derived with the assistance of the first order shear deformation theory (FSDT), Hamilton’s principle and energy method. Besides, In order to solve motion equations and analyze dynamic instability region (DIR) of the structure, mixed model of differential quadrature method (DQM) and Bolotin’s method is used. Moreover, investigation of the different parameters effects such as geometrical parameters and volume fraction of CNTs on the analysis of the DIR of the structure is done. In accordance with the obtained results, the DIR will occur at higher frequencies by increasing the volume fraction of CNTs.

      • KCI등재

        Stress and Electric Potential Fields in Piezoelectric Smart Spheres

        A. Ghorbanpour,S. Golabi,M. Saadatfar 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.11

        Piezoelectric materials produce an electric field by deformation, and deform when subjected to an electric field. The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices, including electric-mechanical actuators, sensors and structures. In this paper, a hollow sphere composed of a radially polarized spherically anisotropic piezoelectric material, e.g., PZT_5 or (Pb) (CoW) TiO₃ under internal or external uniform pressure and a constant potential difference between its inner and outer surfaces or combination of these loadings has been studied. Electrodes attached to the inner and outer surfaces of the sphere induce the potential difference. The governing equilibrium equations in radially polarized form are shown to reduce to a coupled system of second-order ordinary differential equations for the radial displacement and electric potential field. These differential equations are solved analytically for seven different sets of boundary conditions. The stress and the electric potential distributions in the sphere are discussed in detail for two piezoceramics, namely PZT_5 and (Pb) (CoW) TiO₃. It is shown that the hoop stresses in hollow sphere composed of these materials can be made virtually uniform across the thickness of the sphere by applying an appropriate set of boundary conditions.

      • SCIESCOPUSKCI등재

        Stress and Electric Potential Fields in Piezoelectric Smart Spheres

        Ghorbanpour, A.,Golabi, S.,Saadatfar, M. The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.11

        Piezoelectric materials produce an electric field by deformation, and deform when subjected to an electric field. The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices, including electric-mechanical actuators, sensors and structures. In this paper, a hollow sphere composed of a radially polarized spherically anisotropic piezoelectric material, e.g., PZT_5 or (Pb) (CoW) $TiO_3$ under internal or external uniform pressure and a constant potential difference between its inner and outer surfaces or combination of these loadings has been studied. Electrodes attached to the inner and outer surfaces of the sphere induce the potential difference. The governing equilibrium equations in radially polarized form are shown to reduce to a coupled system of second-order ordinary differential equations for the radial displacement and electric potential field. These differential equations are solved analytically for seven different sets of boundary conditions. The stress and the electric potential distributions in the sphere are discussed in detail for two piezoceramics, namely PZT _5 and (Pb) (CoW) $TiO_3$. It is shown that the hoop stresses in hollow sphere composed of these materials can be made virtually uniform across the thickness of the sphere by applying an appropriate set of boundary conditions.

      • KCI등재
      • KCI등재

        Buckling analysis of multi-walled carbon nanotubes under combinedloading considering the effect of small length scale

        A. Ghorbanpour Arani,R. Rahmani,A. Arefmanesh,S. Golabi 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.3

        The torsional and axially compressed buckling of an individual embedded multi-walled carbon nanotube (MWNTs) subjected to an internal and/or external radial pressure was investigated in this study. The emphasis is placed on new physical phenomena which are due to both the small length scale and the surrounding elastic medium. Multiwall carbon nanotubes which are considered in this study are classified into three categories based on the radius to thickness ratio, namely, thin, thick, and almost solid. Explicit formulas are derived for the van der Waals (vdW) interaction between any two layers of an MWNT based on the continuum cylindrical shell model. In most of the previous studies, the vdW interaction between two adjacent layers was considered only and the vdW interaction among other layers was neglected. Moreover, in these works, the vdW interaction coefficient was treated as a constant that was independent of the radii of the tubes. However, in the present model the vdW interaction coefficients are considered to be dependent on the change of interlayer spacing and the radii of the tubes. The effect of the small length scale is also considered in the present formulation. The results show that there is a unique buckling mode (m,n) corresponding to the critical shear stress. This result is obviously different from what is expected for the pure axially compressed buckling of an individual multi-walled carbon nanotube.

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