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    Öğe
    Geometrically nonlinear transient analysis of laminated composite super-elliptic shell structures with generalized differential quadrature method
    (Pergamon-Elsevier Science Ltd, 2018) Akgun, Gokce; Kurtaran, Hasan
    In this study, geometrically nonlinear dynamic behavior of laminated composite super-elliptic shells is investigated using generalized differential quadrature method. Super-elliptic shell can represent cylindrical, elliptical or quasi-rectangular shell by adjusting parameters in super-ellipse formulation (also known as Lame curve formulation). Geometric nonlinearity is taken into account using Green-Lagrange nonlinear strain-displacement relations that are derived using differential geometry and theory of surfaces. Transverse shear effect is considered through the first-order shear deformation theory. Equation of motion is obtained using virtual work principle. Spatial derivatives in equation of motion is expressed with generalized differential quadrature method and time integration is carried out using Newmark average acceleration method. Several super-elliptic shell problems under uniform distributed load are solved with the proposed method. Effects of layer orientations, boundary conditions, ovality and ellipticity on dynamic behavior are investigated. Transient responses are compared with finite element solutions.
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    Öğe
    Large displacement transient analysis of FGM super-elliptic shells using GDQ method
    (Elsevier Sci Ltd, 2019) Akgun, Gokce; Kurtaran, Hasan
    Current work concentrates on large displacement dynamic analysis of super-elliptic (SE) shells made of functionally graded materials (FGMs) employing generalized differential quadrature (GDQ) technique. SE shells can be in quasi-rectangular, elliptical or cylindrical shell forms according to the parameters in super-ellipse formulation. In this paper, large displacements are considered through Green-Lagrange nonlinear strain-displacement relationships derived for SE shells with full nonlinearity in transverse shear. Present solution is based on first-order shear deformation theory (FSDT). Virtual work principle and GDQ method are utilized to derive equation of motion and to express spatial derivatives existing in equation of motion, respectively. Newmark average acceleration method is employed in the solution of equation of motion. By solving various FGM super-elliptic (FGM-SE) shell problems, effects of FGM material properties (using different ceramic/metal pairs like Alumina/Steel (Al2O3/Steel), Zirconia/Aluminum (ZrO2/Al), Alumina/Aluminum (Al2O3/Al), Zirconia/Monel (ZrO2/Ni-Cu) and Silicon Nitride/Steel (Si3N4/Steel)), SE geometric characteristics (ellipticity and ovality) and boundary conditions on dynamic response are investigated.
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    Non-linear transient response of porous functionally graded truncated conical panels using GDQ method
    (Elsevier Sci Ltd, 2021) Akgun, Gokce; Kurtaran, Hasan; Kalbaran, Ozgur
    Present study deals with large displacement transient dynamic response of truncated conical panels made of Porous Functionally Graded Materials (P-FGMs) using Generalized Differential Quadrature (GDQ) method. In this study, geometric non-linearity is taken into consideration through Green-Lagrange non-linear strain-displacement relations. First order shear deformation theory (FSDT) is utilized to take transverse shear effects into account. Virtual work principle is used to derive the equation of motion. The solution methodology utilizes GDQ method for spatial discretization of the variables. Newmark average acceleration method is implemented in time integration. Effects of different types of porosity distribution, porosity ratio and conical parameters on non-linear transient behavior of truncated conical panels are investigated for functionally graded material made of Zirconia/Aluminum (ZrO2/Al) considering various volume fraction coefficients.