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      • SCIESCOPUS

        An efficient and simple refined theory for free vibration of functionally graded plates under various boundary conditions

        Zouatnia, Nafissa,Hadji, Lazreg,Kassoul, Amar Techno-Press 2018 Geomechanics & engineering Vol.16 No.1

        In this paper an efficient and simple refined shear deformation theory is presented for the free vibration of Functionally Graded Plates Under Various Boundary Conditions. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The number of independent unknowns of present theory is four, as against five in other shear deformation theories. The plates are considered of the type having two opposite sides simply-supported, and the two other sides having combinations of simply-supported, clamped, and free boundary conditions. The mechanical properties of functionally graded material are assumed to vary according to power law distribution of the volume fraction of the constituents. Equations of motion are derived using Hamilton's principle. The results of this theory are compared with those of other shear deformation theories. Various numerical results including the effect of boundary conditions, power-law index, plate aspect ratio, and side-to-thickness ratio on the free vibration of FGM plates are presented.

      • SCIESCOPUS

        A refined hyperbolic shear deformation theory for bending of functionally graded beams based on neutral surface position

        Zouatnia, Nafissa,Hadji, Lazreg,Kassoul, Amar Techno-Press 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.5

        In this paper, a hyperbolic shear deformation theory is presented for bending analysis of functionally graded beams. This theory used in displacement field in terms of thickness co-ordinate to represent the shear deformation effects and does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the virtual work principle and the physical neutral surface concept. A simply supported functionally graded beam subjected to uniformly distributed loads and sinusoidal loads are consider for detail numerical study. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

      • SCIESCOPUS

        An analytical solution for bending and vibration responses of functionally graded beams with porosities

        Zouatnia, Nafissa,Hadji, Lazreg,Kassoul, Amar Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.25 No.4

        This work presents a static and free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. A new displacement field containing integrals is proposed which involves only three variables. Based on the suggested theory, the equations of motion are derived from Hamilton's principle. This theory involves only three unknown functions and accounts for parabolic distribution of transverse shear stress. In addition, the transverse shear stresses are vanished at the top and bottom surfaces of the beam. The Navier solution technique is adopted to derive analytical solutions for simply supported beams. The accuracy and effectiveness of proposed model are verified by comparison with previous research. A detailed numerical study is carried out to examine the influence of the deflections, stresses and natural frequencies on the bending and free vibration responses of functionally graded beams.

      • Static and free vibration behavior of functionally graded sandwich plates using a simple higher order shear deformation theory

        Zouatnia, Nafissa,Hadji, Lazreg Techno-Press 2019 Advances in materials research Vol.8 No.4

        The objective of the present paper is to investigate the bending and free vibration behavior of functionally graded material (FGM) sandwich rectangular plates using an efficient and simple higher order shear deformation theory. Unlike other theories, there are only four unknown functions involved, as compared to five in other shear deformation theories. The most interesting feature of this theory is that it does not require the shear correction factor. Two common types of FGM sandwich plates are considered, namely, the sandwich with the FGM facesheet and the homogeneous core and the sandwich with the homogeneous facesheet and the FGM core. The equation of motion for the FGM sandwich plates is obtained based on Hamilton's principle. The closed form solutions are obtained by using the Navier technique. A static and free vibration frequency is given for different material properties. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

      • KCI등재

        A refined hyperbolic shear deformation theory for bending of functionally graded beams based on neutral surface position

        Nafissa Zouatnia,Lazreg Hadji,Amar Kassoul 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.5

        In this paper, a hyperbolic shear deformation theory is presented for bending analysis of functionally graded beams. This theory used in displacement field in terms of thickness co-ordinate to represent the shear deformation effects and does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the virtual work principle and the physical neutral surface concept. A simply supported functionally graded beam subjected to uniformly distributed loads and sinusoidal loads are consider for detail numerical study. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

      • SCIESCOPUS

        Bending analysis of FGM plates using a sinusoidal shear deformation theory

        Hadji, Lazreg,Zouatnia, Nafissa,Kassoul, Amar Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

        The response of functionally graded ceramic-metal plates is investigated using theoretical formulation, Navier's solutions, and a new displacement based on the high-order shear deformation theory are presented for static analysis of functionally graded plates. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. Numerical results of the new refined plate theory are presented to show the effect of the material distribution on the deflections, stresses and fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the static and free vibration behavior of functionally graded plates.

      • KCI등재

        An analytical solution for bending and free vibration responses of functionally graded beams with porosities: Effect of the micromechanical models

        Lazreg Hadji,Nafissa Zouatnia,Fabrice Bernard 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

        In this paper, a new higher order shear deformation model is developed for static and free vibration analysis of functionally graded beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. Different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. In addition, the effect of different micromechanical models on the bending and free vibration response of these beams is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG beams whose properties vary continuously across the thickness according to a simple power law. Based on the present higher-order shear deformation model, the equations of motion are derived from Hamilton’s principle. Navier type solution method was used to obtain displacement, stresses and frequencies, and the numerical results are compared with those available in the literature. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, micromechanical models, mode numbers, and geometry on the bending and natural frequencies of imperfect FG beams.

      • KCI등재

        Wave propagation in functionally graded beams using various higher-order shear deformation beams theories

        Lazreg Hadji,Nafissa Zouatnia,Amar Kassoul 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.2

        In this work, various higher-order shear deformation beam theories for wave propagation in functionally graded beams are developed. The material properties of FG beam are assumed graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, the governing equations of the wave propagation in the FG beam are derived by using the Hamilton’s principle. The analytic dispersion relations of the FG beam are obtained by solving an eigenvalue problem. The effects of the volume fraction distributions on wave propagation of functionally graded beam are discussed in detail. The results carried out can be used in the ultrasonic inspection techniques and structural health monitoring.

      • KCI등재

        Bending analysis of FGM plates using a sinusoidal shear deformation theory

        Lazreg Hadji,Nafissa Zouatnia,Amar Kassoul 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

        The response of functionally graded ceramic-metal plates is investigated using theoretical formulation, Navier's solutions, and a new displacement based on the high-order shear deformation theory are presented for static analysis of functionally graded plates. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. Numerical results of the new refined plate theory are presented to show the effect of the material distribution on the deflections, stresses and fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the static and free vibration behavior of functionally graded plates.

      • SCIESCOPUS

        An analytical method for free vibration analysis of functionally graded sandwich beams

        Bouakkaz, K.,Hadji, L.,Zouatnia, N.,Adda Bedia, E.A. Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.1

        In this paper, a hyperbolic shear deformation beam theory is developed for free vibration analysis of functionally graded (FG) sandwich beams. The theory account for higher-order variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. The material properties of the functionally graded sandwich beam are assumed to vary according to power law distribution of the volume fraction of the constituents. The core layer is still homogeneous and made of an isotropic material. Based on the present refined beam theory, the equations of motion are derived from Hamilton's principle. Navier type solution method was used to obtain frequencies. Illustrative examples are given to show the effects of varying gradients and thickness to length ratios on free vibration of functionally graded sandwich beams.

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