Browsing by Author "Aykul, H"

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    Elastic-plastic stress analysis and plastic zone propagation in fibre-reinforced thermoplastic laminates using finite element method
    Aykul, H; Atas, C; Akbulut, H
    The results of a study of elastic-plastic stress analysis and plastic zone propagation in a low density polyethylene thermoplastic composite plate subjected to uniform transverse load are presented. Thermoplastic matrix, polyethylene (LDPE), and steel fibres were used to fabricate the composite plates. Yield points and elastic, elastic-plastic and residual stresses are calculated numerically for both symmetric and antisymmetric laminated plates with different ply orientations by using Finite Element Method. First order shear deformation theory was used as an equivalent single-layer laminate theory for small deformations. Contour plots corresponding to 100, 150 and 200 load steps display the expansion of the plastic zone. Mechanical properties of a layer were obtained experimentally.
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    Elasto-plastic stress analysis of aluminum metal matrix laminated plates with a circular hole under transverse loading
    Sayman, O; Aykul, H
    Metal-matrix composites provide new materials with superior properties. They give high strength and stiffness and fatigue properties. In this study, a stainless steel fiber reinforced aluminum metal-matrix laminated simply supported plate with a circular hole is loaded transversely. Elastic, elasto-plastic and residual stresses are calculated in the symmetric and/or antisymmetric cross-ply and angle-ply laminated plate for small deformations by using finite elements method. Load steps are chosen 200, 400 and 600. Isoparametric quadrilateral element with nine node is developed for the elasto-plastic analysis. Metal-matrix composite laminated plate is manufactured by using moulds under the action of 30 MPa and heating up 600degreesC. The first-order shear deformation theory is used in the study.
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    A calculation of stress distribution in metal-porcelain crowns by using three-dimensional finite element method
    Aykul, H; Toparli, M; Dalkiz, M
    The objective of this study was to calculate stress distribution in a maxillary second premolar tooth which occurred by the mastication force. The tooth model was crowned with Au-Pd alloy, Ni-Cr alloy and porcelain. A load of 450 N, at an angle of 45degrees to the longitudinal axis was applied on the occlusal margin of the crown tooth. The tooth was assumed isotropic, homogenous, elastic and unsymmetrical. This numerical study was carried out using three-dimensional finite element models and calculation programs were prepared by the authors using FORTRAN 77. The distribution of compressive, tensile and shear stress were plotted for the dentine, dentine-metal and metal-porcelain interfaces. The highest stress values were observed when Ni-Cr alloy and porcelain was used.
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    An elastic/plastic solution for a thermoplastic composite cantilever beam loading by bending moment
    Sayman, O; Aksoy, S; Aykul, H
    In this study, an elastic/plastic stress analysis is carried out for a thermoplastic composite cantilever beam loaded by a bending moment at the free end. The composite beam is reinforced by woven steel fibers, at 0, 15, 30 and 45 degrees orientation angles. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli-Navier hypotheses. It is found that the intensity of the residual stress component of sigma (x) is a maximum at the upper and lower surfaces. The composite material is assumed to be as hardening linearly. The Tsai-Hill theory is used as a yield criterion. (C) 2000 Elsevier Science Ltd. All rights reserved.