Showing papers on "Functionally graded material published in 2005"
TL;DR: In this paper, the impact of the core thickness, relative to the total thickness of the plate, on the critical buckling load and the eigenfrequencies of the vibration natural frequency is investigated.
399 citations
TL;DR: In this paper, a two-dimensional solution for bending analysis of simply supported ceramic-metal sandwich plates is presented, where the sandwich plate faces have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity and Poisson's ratio of the faces are assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents.
336 citations
TL;DR: In this article, an exact solution for the multilayered rectangular plate made of functionally graded, anisotropic, and linear magneto-electro-elastic materials is presented.
309 citations
TL;DR: In this article, the authors investigated dynamic failure processes in homogeneous and functionally graded materials (FGMs) and incorporated the failure criterion in the cohesive zone model (CZM) using both a finite cohesive strength and work to fracture in the material description.
199 citations
TL;DR: In this article, a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material is presented, where the temperature distribution is assumed to be a function of radius.
162 citations
TL;DR: In this paper, a nonlinear formulation developed based on von Karman's assumptions is employed to study the free vibration characteristics of functionally graded material (FGM) plates subjected to thermal environment.
156 citations
TL;DR: In this paper, an in situ processing method involving impregnation of a dense, fine-grained alumina by an aluminosilicate glass was employed to fabricate such a composite.
Abstract: Hertzian (spherical) indentation experiments were carried out in a graded alumina-glass composite whose Young`s modulus increased with depth beneath the indented surface. An in situ processing method involving impregnation of a dense, fine-grained alumina by an aluminosilicate glass was employed to fabricate such a composite. With this technique, a monotonic, unidirectional variation in Young`s modulus of as much as 50% was introduced over a distance of approximately 2 mm, while keeping the coefficient of thermal expansion and the Poisson ratio for the glass and the alumina nearly the same. The macroscopically graded, elastic composite so produced with nearly full density has essentially no macroscopic, long-range residual stresses following processing. The unidirectional variation in Young`s modulus under the indenter is shown to fully suppress the formation of Hertzian cone cracks. Without these elastic-modulus gradients, cone-crack formation was observed in bulk glass and alumina. Finite-element analyses of spherical indentation on elastically graded substrates were also performed to develop a quantitative understanding of the experimental trends. It is reasoned that the present innovations, involving functionally graded surfaces and their in situ processing, provide new possibilities for enhancing certain contact-damage resistance characteristics in various ceramic materials for a broad range of engineering applications. Furthermore,more » this contact-damage-resistance phenomenon in functionally graded ceramics is elastic in nature, and is, therefore, likely to be immune to mechanical fatigue within the elastic limit.« less
143 citations
TL;DR: In this paper, the problems of thermal buckling in axial direction of cylindrical shells made of functionally graded materials are discussed based on the Donnell's shell theory, and closed form solutions are presented for the shell with simply supported boundary conditions subjected to three types of thermal loading.
133 citations
TL;DR: In this article, an analytical solution is provided for the postbuckling behavior of moderately thick plates and shallow shells made of functionally graded materials (FGMs) under edge compressive loads and a temperature field.
131 citations
TL;DR: In this article, the effect of randomness on the elastic buckling of FGM rectangular plates which are resting on an elastic foundation and subjected to uniform in-plane edge compressions is investigated.
127 citations
TL;DR: In this paper, a mesh-free model is presented for active shape control as well as the dynamic response repression of the functionally graded material (FGM) plate containing distributed piezoelectric sensors and actuators.
TL;DR: In this article, the authors investigated the stochastic bending response of moderately thick, compositionally graded plates with uncertainties of low variability and subjected to lateral load and uniform temperature change and found that the response sensitivity of the plate is very much dependent on the material composition.
25 Jan 2005-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a linear compositional gradient from 100% SS316L stainless steel to 100% Rene88DT superalloy was achieved within a thickness of 40mm of laser multilayer deposition.
Abstract: The stainless steel-SS316L/superalloy-Rene88DT graded material was successfully fabricated using laser rapid forming A linear compositional gradient, from 100% SS316L stainless steel to 100% Rene88DT superalloy, was achieved within a thickness of 40 mm of laser multilayer deposition The solidification behavior and the morphological evolution along the compositional gradient were investigated It was found that, in the gradient zone, within the processing parameters of this study, there was continued epitaxial growth of the γ phase of the columnar dendrites, starting with 100% SS316L stainless steel to 100% Rene88DT superalloy, with the 〈1 0 0〉 crystallographic orientation parallel to the gradient direction Clad layer bandings were found in the samples; however, the continuity of the growth of the columnar dendrites was not upset The results are explained by the columnar to equiaxed transition theory and the criteria for planar interface instability and dendritic growth
TL;DR: In this paper, a postbuckling analysis for a shear deformable functionally graded cylindrical shell of finite length subjected to combined axial and radial loads in thermal environments is presented.
TL;DR: In this paper, the effects of Young's modulus of the outer layer and the geometric size of the middle layer on the deformations and stresses in the vessels consisting of the three different layers are examined.
TL;DR: In this paper, Al2O3/ZrO2 functionally graded thermal barrier coating (FG-TBC) was proposed as a potential candidate as an interlayer to improve the oxidation resistance of TBC due to its low oxygen diffusivity.
Abstract: Coupled with functionally graded materials (FGM) concept, Al2O3 was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating (TBC) system due to its low oxygen diffusivity. Plasma spray process was utilized to produce Al2O3/ZrO2 functionally graded thermal barrier coating (FG-TBC). This article discusses physical and mechanical properties, thermal behavior, and high-temperature oxidation resistance of the FG-TBC system as compared to a typical duplex TBC system. The results showed that the proposed FG systems exhibit superior mechanical properties and oxidation resistance at the expense of a slightly lower thermal-insulating effect. Thin interlayer is preferred in order to minimize the detrimental effect of phase transformation of γ-Al2O3 to α-Al2O3 that results in tensile residual stresses at the interface.
TL;DR: In this article, the thermomechanical properties of the mullite/Mo system had graded distributions that depend on the composition variation across the thickness, and the mechanism of crack formation was discussed.
TL;DR: A postbuckling analysis for a functionally graded cylindrical shell with piezoelectric actuators subjected to axial compression combined with electric loads in thermal environments is presented in this article.
TL;DR: In this article, the authors examined the three dimensional surface crack problems in functionally graded coatings subjected to mode I mechanical or transient thermal loading and computed the stress intensity factors by using the displacement correlation technique.
Abstract: The main objective of this study is to examine the three dimensional surface crack problems in functionally graded coatings subjected to mode I mechanical or transient thermal loading. The surface cracks are assumed to have a semi-elliptical crack front profile of arbitrary aspect ratio. The cracks are embedded in the functionally graded material (FGM) coating which is perfectly bonded to a homogeneous substrate. A three dimensional finite element method is used to solve the thermal and structural problems. Collapsed 20-node isoparametric elements are utilized to simulate the strain singularity around the crack front. The stress intensity factors are computed by using the displacement correlation technique. Four different coating types are considered in the analyses which have homogeneous, ceramic-rich (CR), metal-rich (MR) and linear variation (LN) material composition profiles. In the mechanical loading problems, the composite medium is assumed to be subjected to fixed-grip tension or three point bending. In the thermal analysis, a transient residual stress problem is considered. The stress intensity factors calculated for FGM plates are in good agreement with the previously published results on three dimensional surface cracks. The new results provided show that maximum stress intensity factors computed during transient thermal loading period for the FGM coatings are lower than those of the homogeneous ceramic ones.
TL;DR: In this article, the authors used the first-order shear deformation shell theory (FSDT) to study the vibration suppression characteristics of functionally graded material (FGM) shells with embedded magnetostrictive layers.
TL;DR: In this paper, the theoretical treatment of transient thermoelastic problem involving a functionally graded rectangular plate due to non-uniform heat supply was studied. But the authors only considered the case of a simple supported rectangular plate and did not consider the nonhomogeneity of the material.
TL;DR: In this article, an exact analysis of a functionally graded piezothermo-electric rectangular plate that is simply supported, electrically grounded and isothermal on its four lateral edges is presented.
Abstract: This paper presents an exact analysis of a functionally graded piezothermo-electric rectangular plate that is simply supported, electrically grounded and isothermal on its four lateral edges. The governing equations are established for an orthotropic functionally graded piezothermoelectric plate under an assumption that the mechanical, electrical, and thermal properties of the material have the same exponential dependence on the thickness-coordinate. An exact three-dimensional general solution in the form of double Fourier series is derived for arbitrary distributions of combined mechanical, electrical, and thermal loadings at the top and bottom surfaces of the plate. Numerical results are presented for three special cases of uniformly distributed loads at the top and bottom surfaces of the plate, and the effect of truncation of the series on the accuracy of the solution is discussed.
TL;DR: In this article, the displacement components are expressed by trigonometric series representation through the plate thickness to develop a two-dimensional theory, which is used to perform free-vibration analysis of a simply supported functionally graded thick plate.
Abstract: The displacement components are expressed by trigonometric series representation through the plate thickness to develop a two-dimensional theory. This trigonometric shear deformation plate theory is used to perform free-vibration analysis of a simply supported functionally graded thick plate. Lame's coefficients and density for the material of the plate are assumed to vary in the thickness direction only. Effects of rotatory inertia are considered in the present theory and the vibration natural frequencies are investigated. The results obtained from this theory are compared with those obtained from a 3D elasticity analysis and various equivalent theories that are available. A detailed analysis is carried out to study the various natural frequencies of functionally graded material plates. The influences of the transverse shear deformation, plate aspect ratio, side-to-thickness ratio and volume fraction distributions are investigated.
TL;DR: In this article, a three-dimensional analysis of the static response of a clamped rectangular plate made of functionally graded material is presented, where the governing equation of the plate is derived by the Ritz energy method within the linear, small deformation theory of elasticity.
Abstract: A three-dimensional study for the static response of a clamped rectangular plate made of functionally graded material is presented. The governing equation of the plate is derived by the Ritz energy method within the linear, small deformation theory of elasticity. A power-law distribution for the mechanical characteristics is adopted to model the continuous variation of properties from those of one component to those of the other. The displacements and stresses of the plate for different values of the power-law exponent and thickness-side ratios are investigated. The developed three-dimensional elasticity solution by the multiterm Ritz method appears to be important because it can be used to assess the accuracy of both the two-dimensional theories as well as that of the numerical methods.
TL;DR: In this paper, the fracture behavior of thermal barrier-type functionally graded material (FGM) coatings under high heat flux was investigated and the results of thermal cycling test with a surface temperature of 1400 °C (during heating) showed that there existed a great difference in fracture location between different specimens.
Abstract: The objective of this research was to study heat insulation performance and fracture behavior of thermal barrier-type functionally graded material (FGM) coatings under high heat flux. The FGM coatings with thicknesses varying from 0.75 to 2.1 mm were designed and deposited onto a steel substrate by plasma spraying. With the high heat flux of 0.68 MW m−2, the thickest specimen exhibits a high surface temperature of 1690 °C and the corresponding temperature difference between the top surface and the bottom surface of the coating is high up to 760 °C. The results of thermal cycling test with a surface temperature of 1400 °C (during heating) showed that there existed a great difference in fracture location between different specimens. Fracture behavior of the coatings at surface temperatures of 1500, 1600 and 1700 °C was also investigated. The coating thickness and surface temperature were found to influence the number and the length of cracks. The specimen with the coating thickness of 1.1 mm is the most susceptible to local spallation at the top ceramic coat, while the thickest FGM coating is the most susceptible to cracking at the interface close to the bond coat. Heating time also had an effect on cracking behavior. These results provided some necessary information for appropriate design of FGM coatings to sustain higher temperatures and gradients than those in today's applications.
TL;DR: In this article, the thermal buckling load of a curved beam made of functionally graded material (FGM) with doubly symmetric cross section is considered, where the stability equations are derived using the variational principles.
Abstract: In this paper the thermal buckling load of a curved beam made of functionally graded material (FGM) with doubly symmetric cross section is considered. By instability conditions we mean the in-plane and out-of-plane buckling. The stability equations are derived using the variational principles. The curved beam is under temperature rise for thermal loading. The solution for critical thermal buckling load is obtained using the stability equations and the Galerkin method. The critical thermal buckling load is obtained.
TL;DR: A novel approach of representation and process planning for SFF of FGM objects, termed as equal distance offset (EDO), is proposed, in which an arbitrary-shaped 3D FGM object with linear or non-linear composition gradients can be represented and fabricated via suitable SFF machines.
Abstract: This paper deals with the representation and process planning for solid freeform fabrication (SFF) of 3D functionally graded material (FGM) objects. A novel approach of representation and process planning for SFF of FGM objects, termed as equal distance offset (EDO), is proposed. In EDO, a neutral arbitrary 3D CAD model is adaptively sliced into a series of 2D layers. Within each layer, 2D material gradients are designed and represented via dividing the 2D shape into several sub-regions enclosed by iso-composition contours. If needed, the material composition gradient within each of the sub-regions can be further specified by applying the equal distance offset algorithm to each sub-region. Using this approach, an arbitrary-shaped 3D FGM object with linear or non-linear composition gradients can be represented and fabricated via suitable SFF machines.
TL;DR: In this paper, a three-dimensional elastic stress state of an adhesively bonded single lap joint with functionally graded adherends in tension was investigated, where the adhesive layer experiences stress concentrations along the left and right free edges in the horizontal plane, and the normal stresses and the shear stress are critical.
TL;DR: In this paper, a symmetric Galerkin formulation and implementation for heat conduction in a three-dimensional functionally graded material is presented, where the main task is the evaluation of hypersingular and singular integrals, which is carried out using a direct ‘limit to the boundary' approach.
Abstract: A symmetric Galerkin formulation and implementation for heat conduction in a three-dimensional functionally graded material is presented. The Green's function of the graded problem, in which the thermal conductivity varies exponentially in one co-ordinate, is used to develop a boundary-only formulation without any domain discretization. The main task is the evaluation of hypersingular and singular integrals, which is carried out using a direct ‘limit to the boundary’ approach. However, due to complexity of the Green's function for graded materials, the usual direct limit procedures have to be modified, incorporating Taylor expansions to obtain expressions that can be integrated analytically. Several test examples are provided to verify the numerical implementation. The results of test calculations are in good agreement with exact solutions and corresponding finite element method simulations. Copyright © 2004 John Wiley & Sons, Ltd.
TL;DR: In this article, a plane strain analytical solution to functionally graded elastic and elastic-plastic pressurized tube problems is obtained in the framework of small deformation theory, where the modulus of elasticity of the tube material is assumed to vary radially according to a 2 parametric model in a general parabolic form.
Abstract: Plane strain analytical solutions to functionally graded elastic and elastic-plastic pressurized tube problems are obtained in the framework of small deformation theory. The modulus of elasticity of the tube material is assumed to vary radially according to a 2 parametric model in a general parabolic form. The analytical plastic model is based on Tresca's yield criterion, its associated flow rule and ideally plastic material behavior. Exact solutions of field equations for elastic and plastic deformations are obtained. It is shown that the elastoplastic response of the functionally graded pressurized tube is affected notably by the radial variation of modulus of elasticity. It is also shown mathematically that the nonhomogeneous solution presented here reduces to that of a homogeneous one by the appropriate choice of the material parameters.