International Journal of Engineering & Applied Sciences

1-21

Authors: Francesco Tornabene [1] , Nicholas Fantuzzi [2] , Michele Bacciocchi [3]

The authors are presenting a novel formulation based on the Differential Quadrature (DQ) method which is used to approximate derivatives and integrals. The resulting scheme has been termed strong and weak form finite elements (SFEM or WFEM), according to the numerical scheme employed in the computation. Such numerical methods are applied to solve some structural problems related to the mechanical behavior of plates and shells, made of isotropic or composite materials. The main differences between these two approaches rely on the initial formulation – which is strong or weak (variational) – and the implementation of the boundary conditions, that for the former include the continuity of stresses and displacements, whereas in the latter can consider the continuity of the displacements or both. The two methodologies consider also a mapping technique to transform an element of general shape described in Cartesian coordinates into the same element in the computational space. Such technique can be implemented by employing the classic Lagrangian-shaped elements with a fixed number of nodes along the element edges or blending functions which allow an “exact mapping” of the element. In particular, the authors are employing NURBS (Not-Uniform Rational B-Splines) for such nonlinear mapping in order to use the “exact” shape of CAD designs.

39-54

Authors: Ali Ghorbanpour Arani [1] , Elham Haghparast [2] , Hassan BabaAkbar Zarei [3]

In the present research, vibration and instability of axially moving sandwich plate made of soft core and composite face sheets under initial tension is investigated. Single-walled carbon nano-tubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Higher order shear deformation theory (HSDT) is utilized due to its accuracy of polynomial functions than other plate theories. Based on extended rule of mixture, the structural properties of composite face sheets are taken into consideration. Motion equations are obtained by means of Hamilton’s principle and solved analytically. Influences of various parameters such as axially moving speed, volume fraction of CNTs, pre-tension, thickness and aspect ratio of sandwich plate on the vibration characteristics of moving system are discussed in details. The results indicated that the critical speed of moving sandwich plate is strongly dependent on the volume fraction of CNTs. Therefore, the critical speed of moving sandwich plate can be improved by adding appropriate values of CNTs. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.

66-87

Authors: Vebil Yildirim

Heat-induced, pressure-induced, and centrifugal force-induced axisymmetric exact deformation and stresses in a thick-walled spherical vessel, a cylindrical vessel, and a uniform disk are all determined analytically at a specified constant surface temperature and at a constant angular velocity. The inner and outer pressures are both included in the formulation of annular structures made of an isotropic and homogeneous linear elastic material. Governing equations in the form of Euler-Cauchy differential equation with constant coefficients are solved and results are presented in compact forms. For disks, three different boundary conditions are taken into account to consider mechanical engineering applications. The present study is also peppered with numerical results in graphical forms.

112-126

Authors: Vebil Yildirim

Thermal analyses of radially functionally graded (FG) thick-walled a spherical vessel and an infinite cylindrical vessel or a circular annulus are conducted analytically by the steady-state 1-D Fourier heat conduction theory under Dirichlet’s boundary conditions. By employing simple-power material grading pattern the differential equations are obtained in the form of Euler-Cauchy types. Analytical solution of the differential equations gives the temperature field and the heat flux distribution in the radial direction in a closed form. Three different physical metal-ceramic pairs first considered to study the effect of the aspect ratio, which is defined as the inner radius to the outer radius of the structure, on the temperature and heat flux variation along the radial coordinate. Then a parametric study is performed with hypothetic inhomogeneity indexes for varying aspect ratios.

138-146

Authors: Kadir Mercan [1] , Ömer Civalek [2]

Aorta artery is the most vital artery in humans and almost all animals. Aorta artery is also the largest artery in human body. This artery is the first artery coming out from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller iliac arteries. Aorta artery conveys oxygenated blood to all parts of the body so that this artery is the one, which is under the influence of the highest blood pressure. It is well known that aorta artery consists of three main layers, which cover five sub-layers. In this paper, we aimed to show the difference between functionally graded material (FGM) and laminated composite material and to show which model fits to the structure of aorta artery.

156-168

Authors: Ferhat Erdal [1] , Osman Tunca [2] , Erkan Doğan [3]

Over the past few years there has been sustainable development in the steel and composite construction technology. One of the recent additions to such developments is the I-girders with corrugated web beams. The use of these new generation beams results in a range of benefits, including flexible, free internal spaces and reduced foundation costs. Corrugated web beams are built-up girders with a thin-walled, corrugated web and wide plate flanges. The thin corrugated web affords a significant weight reduction of these beams, compared with hot-rolled or welded ones. In this paper, optimum design of corrugated composite beams is presented. A recent stochastic optimization algorithm coded that is based on hunting search is used for obtaining the solution of the design problem. In the optimisation process, besides the thickness of concrete slab and studs, web height and thickness, distance between the peaks of the two curves, the width and thickness of flange are considered as design variables. The design constraints are respectively implemented from BS EN1993-1:2005 (Annex-D, Eurocode 3) BS-8110 and DIN 18-800 Teil-1. Furthermore, these selections are also carried out such that the design limitations are satisfied and the weight of the composite corrugated web beam is the minimum.