Fethi Kadıoğlu

Influences of elastic foundations and shear deformations on the buckling behavior of functionally graded material truncated conical shells under axial compression

ABSTRACT This article presents an investigation on the buckling of functionally graded (FG) truncated conical shells under an axial load resting on elastic foundations within the shear deformation theory (SDT). The governing equations are solved using the Galerkin method, and the closed-form solution of the axial buckling load for FG conical shells on elastic foundations within the SDT is obtained. Various numerical examples are presented and discussed to verify the accuracy of the closed-form solution in predicting dimensionless buckling loads for FG conical shells on the Winkler–Pasternak elastic foundations within the SDT.

Viscoelastic Behavior of Shear-Deformable Plates

The purpose of this study is to extend a new mixed-type finite element (MFE) model, developed earlier by the present authors for the analysis of viscoelastic Kirchhoff plates [Akoz, A. Y., Kadioglu...

Alternative solution for cross-ply laminated composite thick plates

The structural analysis of orthotropic and linear elastic cross-ply laminated composite thick plates is made by considering complete effects of transverse shear and normal stresses. The solutions are obtained using the functional analysis method in conjunction with the Gâteaux differential. A new functional with boundary condition terms is developed for the analysis. A four-node serendipity element with eight degrees of freedom is used. To ensure the accuracy of the developed mixed finite element (MFE), numerical results are compared with those of the published solutions. It has been proven that the developed MFE is highly accurate and efficient.

Four-Parameter Viscoelastic Model for the Plates of Uniformly Varying Cross-Section

This study aims to investigate the quasi-static response of linear viscoelastic Kirchhoff plates of uniformly varying cross-section subjected to time-dependent loads. Four-parameter solid model is used for defining the linear viscoelastic material behavior. Through an efficient systematic procedure based on the Gâteaux Differential (GD), a functional has been constructed for the analysis. For the analysis, mixed finite element (MFE) method in transformed Laplace-Carson space is used. For transformation of the solutions obtained in the Laplace-Carson domain to the real time domain, Dubner & Abate (D&A) numerical inverse transform technique is employed.

Analysis of Plates under Point Load Using Zener Material Model

In this study, the mixed finite element method in the Laplace-Carson space is developed for viscoelastic plates under point load using Zener material model, utilizing the functional through a systematic procedure based on the Gâteaux Differential. The functional has four independent variables; deflection, two bending moments and one twisting moment in addition to the geometric and dynamic boundary conditions in Laplace-Carson space. The results obtained in the Laplace-Carson domain are converted to real time domain by inverse Laplace transform via Dubner & Abate’s and Durbins algorithms. The performance of the developed solution technique is tested through various quasi-static problems.

An alternative method for analysing buckling of laminated composite beams

In this study, two new functionals are derived based on Gâteaux differential in order to analyse buckling of symmetric cross-ply laminated composite straight beams. The functional comprises four independent variables, i.e. deflection, rotation, shear force and bending moment for Timoshenko beam, and two independent variables, deflection and bending moment, for Euler-Bernoulli beam. The application possibilities and performance of the proposed mixed finite element formulation are presented on several numerical examples.

Dynamic response of visco-elastic plates

In this study, a comprehensive analysis about the dynamic response characteristics of visco-elastic plates is given. To construct the functional in the Laplace-Carson domain for the analysis of visco-elastic plates based on the Kirchhoff hypothesis, functional analysis method is employed. By using this new energy functional in the Laplace-Carson domain, moment values that are important for engineers can be obtained directly with excellent accuracy and element equations can be written explicitly. Three-element model is considered for modelling the visco-elastic material behavior. The solutions obtained in the Laplace-Carson domain by utilizing mixed finite element formulation are transformed to the time domain using the Durbin’s inverse Laplace transform technique. The proposed mixed finite element formulation is shown to be simple to implement and gives satisfactory results for dynamic response of visco-elastic plates.

Viscoelastic Kirchhoff Plate Analysis via Mixed Finite Element Formulation

In this study, a functional for the dynamic analysis of viscoelastic Kirchhoff plates is obtained through an efficient systematic procedure based on the Gâteaux Differential Method. For the solution of the derived functional, mixed finite element method in transformed Laplace-Carson space is used. In this functional, there exists four independent variables such as deflection (w), internal forces (Mx, My, Mxy) in addition to the dynamic and geometric boundary condition terms. For modeling the viscoelastic behavior, four parameter solid model is employed. For transformation of the solutions obtained in the LaplaceCarson domain to the time domain, different numerical inverse transform techniques are employed. The developed solution technique is applied to several dynamic example problems for the verification of the suggested numerical procedure. Keywords—dynamic analysis, viscoelastic plates, Gâteaux differential, mixed finite element method, Laplace-Carson transform