Wyniki wyszukiwania - BazTech

1

Exact and Numerical Elastic Analysis for the FGM Thick-Walled Cylindrical Pressure Vessels with Exponentially-Varying Properties

Nejad M. Z., Abedi M., Lotfian M. H., Ghannad M.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 3

1649--1654

EN

Assuming exponential-varying properties in the radial direction and based on the elasticity theory, an exact closed-form analytical solution is obtained to elastic analysis of FGM thick-walled cylindrical pressure vessels in the plane strain condition. Following this, radial distribution of radial displacement, radial stress, and circumferential stress are plotted for different values of material inhomogeneity constant. The displacements and stresses distributions are compared with the solutions of the finite element method (FEM).

2

Time-dependent thermo-elastic creep analysis of thick-walled spherical pressure vessels made of functionally graded materials

Kashkoli M. D., Nejad M. Z.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 4

1053--1065

EN

Assuming that the thermo-elastic creep response of the material is governed by Norton’s law and material properties, except Poisson’s ratio, are considered as a function of the radius of the spherical vessel, an analytical solution is presented for calculation of stresses and displacements of axisymmetric thick-walled spherical pressure vessels made of functionally graded materials. This analytical solution could be used to study the time and temperature dependence of stresses in spherical vessels made of functionally graded materials. Creep stresses and displacements are plotted against dimensionless radius and time for different values of the powers of the material properties.

3

Absorbed energy by foam-filled quadrangle tubes during the crushing process by considering the interaction effects

Niknejad A., Abedi M. M., Liaghat G. H., Nejad M. Z.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 2

376--391

EN

In this article, some theoretical relations are derived to predict instantaneous crushing force and absorbed energy during initial fold formation in polyurethane foam-filled quadrangle tubes under the axial crushing load. Theoretical analysis is performed based on the energy method. In the theoretical analysis, crushing wavelength is considered as a constant parameter through the process and as a function of column geometrical dimensions. In the analytical calculations, interaction effects between the polyurethane foam and inner wall of quadrangle tubes are considered and a formula is presented to predict absorbed energy by the interaction effects. In the experiment part, some foam-filled specimens were prepared and axially crushed to obtain experimental diagram of crushing force versus axial displacement. Comparison of the theoretical predictions of crushing force and absorbed energy with corresponding experimental results showed a good agreement. Also, it was found that theoretical predictions by considering the interaction effects have a better correlation respect to the experiments.

4

A semi-analytical solution of thick truncated cones using matched asymptotic method and disk form multilayers

Nejad M. Z., Jabbari M., Ghannad M.

Archive of Mechanical Engineering

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2014

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Vol. LXI, nr 3

495--513

EN

In this article, the thick truncated cone shell is divided into disk-layers form with their thickness corresponding to the thickness of the cone. Due to the existence of shear stress in the truncated cone, the equations governing disk layers are obtained based on first shear deformation theory. These equations are in the form of a set of general differential equations. Given that the truncated cone is divided into n disks, n sets of differential equations are obtained. The solution of this set of equations, applying the boundary conditions and continuity conditions between the layers, yields displacements and stresses. The results obtained have been compared with those obtained through the analytical solution and the numerical solution. For the purpose of the analytical solution, use has been made of matched asymptotic method (MAM) and for the numerical solution, the finite element method (FEM).

PL

Grubościenna powłoka stożka ciętego, opisana w artykule, jest dzielona na warstwy w formie krążków o grubości odpowiadającej grubości powłoki. Ponieważ w stożku ściętym istnieją naprężenia ścinające, równania dla warstw krążkowych są otrzymane na bazie teorii odkształceń pierwszego rzędu. Równania te mają postać układu ogólnych równań różniczkowych. Zakładając, że stożek ścięty jest podzielony na n warstw, uzyskuje się układ n równań różniczkowych. Wartości przemieszczeń i naprężeń otrzymuje się w wyniku rozwiązania tego układu równań, przy uwzględnieniu warunków brzegowych i warunków ciągłości. Uzyskane wyniki porównano z wynikami rozwiązań analitycznego oraz numerycznego. Dla potrzeb rozwiązania analitycznego wykorzystano dopasowaną metodę asymptotyczną (Matched Asymptotic Method, MAM), a w rozwiązaniu numerycznym zastosowano metodę elementów skończonych (FEM).

5

Elastic solution of pressurized clamped-clamped thick cylindrical shells made of functionally graded materials

Ghannad M., Nejad M. Z.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 4

1067--1079

EN

The effect of material inhomogeneity on displacements and stresses of an internally pressurized clamped-clamped thick hollow cylinder made of functionally graded materials is investigated. The modulus of elasticity is graded along the radial direction according to power functions of the radial direction. It is assumed that Poisson’s ratio is constant across the cylinder thickness. The governing differential equations were generally derived, making use of the first-order shear deformation theory (FSDT). Following that, the set of non-homogenous linear differential equations for the cylinder with clamped-clamped ends was solved, and the effect of loading and supports on the stresses and displacements was investigated. The problem was also solved, using the finite element method (FEM), the results of which were compared with those of the analytical method.