scholarly journals ON THE LOSS OF STABILITY OF A TWO-LAYERED PLATE MADE OF A FUNCTIONAL-GRADIENT MATERIAL WITH A NON-UNIFORM FIELD OF PRE-STRESSES

2019 ◽  
Vol 81 (4) ◽  
pp. 513-520
Author(s):  
V.V. Eremeev
Keyword(s):  
Constitutive Relation ◽  
Linear Instability ◽  
Functionally Graded ◽  
Initial Stresses ◽  
Gradient Material ◽  
Internal Stresses ◽  
Uniform Field ◽  
Loss Of Stability ◽  
Material Inhomogeneity ◽  
Functional Gradient Material

In the framework of three-dimensional nonlinear elasticity we consider linear instability of a composite plate made of functionally graded material and having initial stresses. The plae consists of two layers which were obtained as a result of flattening of an annual sector of an elastic cylinder. This deformation results in appearance of internal stresses. Thus, the plate becomes initially stressed. The initial stresses depend on the thickness coordinate, so we get inhomogeneous stress field. We have two types of inhomogeneities, the first is the inhomogeneity of the initial stresses whereas the second is the material inhomogeneity.We use the incompressible neo-Hookean material model as a constitutive relation. Despite of relatively simple form this model describes properly severe deformations of some rubber-like materials. For incompressible materials the flattening constitutes one of the so-called universal deformations, that is such deformation which is independent on the choice of constitutive relation. The material inhomogeneity is described through a dependence of the shear modulus on the thickness coordinate. Such inhomogeneity could be related to the manufacturing of the material or to further treatment. The stability was analysed using the linearization approach. We superimpose infinitesimal deformations on the finite initial one. The linearized boundary-value problem was derived and its nontrivial solutions were obtained. The solution was obtained in series of trigonometric functions. This helps to automatically satisfy a part of boundary conditions. We consider the influence of the inhomogeneity and initial stresses. We show that the initial stresses may significantly change critical deformations. For example, the loss of stability is possible due to initial stresses only.

scholarly journals ON THE LOSS OF STABILITY OF A TWO-LAYERED PLATE MADE OF A FUNCTIONAL-GRADIENT MATERIAL WITH A NON-UNIFORM FIELD OF PRE-STRESSES

2019 ◽  
Vol 81 (4) ◽  
pp. 512-518
Author(s):  
V.V. Eremeev
Keyword(s):  
Constitutive Relation ◽  
Linear Instability ◽  
Functionally Graded ◽  
Initial Stresses ◽  
Gradient Material ◽  
Internal Stresses ◽  
Uniform Field ◽  
Loss Of Stability ◽  
Material Inhomogeneity ◽  
Functional Gradient Material

In the framework of three-dimensional nonlinear elasticity we consider linear instability of a composite plate made of functionally graded material and having initial stresses. The plae consists of two layers which were obtained as a result of flattening of an annual sector of an elastic cylinder. This deformation results in appearance of internal stresses. Thus, the plate becomes initially stressed. The initial stresses depend on the thickness coordinate, so we get inhomogeneous stress field. We have two types of inhomogeneities, the first is the inhomogeneity of the initial stresses whereas the second is the material inhomogeneity.We use the incompressible neo-Hookean material model as a constitutive relation. Despite of relatively simple form this model describes properly severe deformations of some rubber-like materials. For incompressible materials the flattening constitutes one of the so-called universal deformations, that is such deformation which is independent on the choice of constitutive relation. The material inhomogeneity is described through a dependence of the shear modulus on the thickness coordinate. Such inhomogeneity could be related to the manufacturing of the material or to further treatment. The stability was analysed using the linearization approach. We superimpose infinitesimal deformations on the finite initial one. The linearized boundary-value problem was derived and its nontrivial solutions were obtained. The solution was obtained in series of trigonometric functions. This helps to automatically satisfy a part of boundary conditions. We consider the influence of the inhomogeneity and initial stresses. We show that the initial stresses may significantly change critical deformations. For example, the loss of stability is possible due to initial stresses only.

scholarly journals Buckling of a composite bar made of a functional-gradient material with an inhomogeneous pre-stress field

2018 ◽  
Vol 226 ◽  
pp. 01014
Author(s):  
Vadim V. Eremeev ◽  
Denis V. Ivashchenko
Keyword(s):  
Stress Field ◽  
Circular Cylinder ◽  
Nonlinear Elasticity ◽  
Linear Instability ◽  
Initial Stresses ◽  
Gradient Material ◽  
Material Inhomogeneity ◽  
Functional Gradient ◽  
Functional Gradient Material ◽  
Graded Material

Within the 3D nonlinear elasticity we discuss the linear instability of a composite bar made of a functially graded material and having initial stresses. The bar consists of two layers which are inflated for a annular wedge of a circular cylinder. We present the linearized boundary0value problem and obtain its non-trivial solutions. The influence of the material inhomogeneity and the initial stresses are discussed.

Development of Modelling Methods for Materials to be Used as Bone Substitutes

2007 ◽  
Vol 361-363 ◽  
pp. 903-906 ◽  
Author(s):  
R. Gabbrielli ◽  
I.G. Turner ◽  
Chris R. Bowen
Keyword(s):  
Mechanical Strength ◽  
Volume Fraction ◽  
Bone Substitutes ◽  
Gradient Material ◽  
Periodic Surfaces ◽  
Triply Periodic ◽  
Functional Gradient Material ◽  
Spatial Periodicity ◽  
Bearing Materials ◽  
Modelling Methods

The demand in the medical industry for load bearing materials is ever increasing. The techniques currently used for the manufacture of such materials are not optimized in terms of porosity and mechanical strength. This study adopts a microstructural shape design approach to the production of open porous materials, which utilizes spatial periodicity as a simple way to generate the models. A set of triply periodic surfaces expressed via trigonometric functions in the implicit form are presented. A geometric description of the topology of the microstructure is necessary when macroscopic properties such as mechanical strength, stiffness and isotropy are required to be optimised for a given value of volume fraction. A distinction between the families of structures produced is made on the basis of topology. The models generated have been used successfully to manufacture both a range of structures with different volume fractions of pores and samples of functional gradient material using rapid prototyping.

NONLINEAR ANALYSIS OF FUNCTIONALLY GRADED CIRCULAR PLATES UNDER DIFFERENT LOADS AND BOUNDARY CONDITIONS

2008 ◽  
Vol 08 (01) ◽  
pp. 131-159 ◽  
Author(s):  
RECEP GUNES ◽  
J. N. REDDY
Keyword(s):  
Nonlinear Analysis ◽  
Strain Tensor ◽  
Homogenization Method ◽  
Functionally Graded ◽  
Gradient Material ◽  
Graphical Form ◽  
Circular Plates ◽  
Geometrically Nonlinear Analysis ◽  
Steady State Heat Transfer ◽  
Lagrange Strain

Geometrically nonlinear analysis of functionally graded circular plates subjected to mechanical and thermal loads is carried out in this paper. The Green–Lagrange strain tensor in its entirety is used in the analysis. The locally effective material properties are evaluated using homogenization method which is based on the Mori–Tanaka scheme. In the case of thermally loaded plates, the temperature variation through the thickness is determined by solving a steady-state heat transfer (i.e. energy) equation. As an example, a functionally gradient material circular plate composed of zirconium and aluminum is used and results are presented in graphical form.

scholarly journals Surface Wave Speed of Functionally Graded Magneto-Electro-Elastic Materials with Initial Stresses

2014 ◽  
Vol 44 (3) ◽  
pp. 49-64 ◽  
Author(s):  
Li Li ◽  
P. J. Wei
Keyword(s):  
Surface Wave ◽  
Boundary Conditions ◽  
Elastic Material ◽  
Short Circuit ◽  
Equations Of Motion ◽  
Open Circuit ◽  
Functionally Graded ◽  
Initial Stresses ◽  
Shear Surface ◽  
Traction Boundary Conditions

Abstract The shear surface wave at the free traction surface of half- infinite functionally graded magneto-electro-elastic material with initial stress is investigated. The material parameters are assumed to vary ex- ponentially along the thickness direction, only. The velocity equations of shear surface wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magneto-electro-elastic material with the initial stresses and the free traction boundary conditions. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are discussed. The investigation provides a basis for the development of new functionally graded magneto-electro-elastic surface wave devices.

Elastic analysis of exponential FGM disks subjected to internal and external pressure

2013 ◽  
Vol 3 (3) ◽  
Author(s):  
Mohammad Nejad ◽  
Majid Abedi ◽  
Mohammad Lotfian ◽  
Mehdi Ghannad
Keyword(s):  
Radial Direction ◽  
Circumferential Stress ◽  
External Pressure ◽  
Functionally Graded ◽  
Elastic Analysis ◽  
The Finite Element Method ◽  
Graded Materials ◽  
Material Inhomogeneity ◽  
Closed Form Analytical Solution ◽  
Stress Profiles

AbstractAssuming exponential varying properties in the radial direction and constant Poisson’s ratio, a closed-form analytical solution based on the elasticity theory is obtained to elastic analysis of disks made of functionally graded materials (FGMs) subjected to internal and external pressure. Following this, radial displacement, radial stress, and circumferential stress profiles are plotted for different values of material inhomogeneity constant, as a function of radial direction. The displacements and stresses distributions are compared with the solutions of the finite element method (FEM) and comparison with the corresponding numerical solution indicates that the proposed solution has excellent convergence and accuracy.

Vibration analysis of a thin functionally graded plate having an out of plane material inhomogeneity resting on Winkler–Pasternak foundation under different combinations of boundary conditions

2018 ◽  
Vol 233 (8) ◽  
pp. 2636-2662 ◽  
Author(s):  
Piyush Pratap Singh ◽  
Mohammad Sikandar Azam ◽  
Vinayak Ranjan
Keyword(s):  
Boundary Conditions ◽  
Power Law ◽  
Functionally Graded Material ◽  
Functionally Graded ◽  
Pasternak Foundation ◽  
Functionally Graded Plate ◽  
Material Inhomogeneity ◽  
Power Law Exponent ◽  
Out Of Plane ◽  
Graded Material

In the present research article, classical plate theory has been adopted to analyze functionally graded material plate, having out of plane material inhomogeneity, resting on Winkler–Pasternak foundation under different combinations of boundary conditions. The material properties of the functionally graded material plate vary according to power law in the thickness direction. Rayleigh–Ritz method in conjugation with polynomial displacement functions has been used to develop a computationally efficient mathematical model to study free vibration characteristics of the plate. Convergence of frequency parameters (nondimensional natural frequencies) has been attained by increasing the number of polynomials of displacement function. The frequency parameters of the functionally graded material plate obtained by proposed method are compared with the open literature to validate the present model. Firstly, the present model is used to calculate first six natural frequencies of the functionally graded plate under all possible combinations of boundary conditions for the constant value of stiffness of Winkler and Pasternak foundation moduli. Further, the effects of density, aspect ratio, power law exponent, Young’s modulus on frequency parameters of the functionally graded plate resting on Winkler–Pasternak foundation under specific boundary conditions viz. CCCC (all edges clamped), SSSS (all edges simply supported), CFFF (cantilever), SCSF (simply supported-clamped-free) are studied extensively. Furthermore, effect of stiffness of elastic foundation moduli (kp and kw) on frequency parameters are analyzed. It has been observed that effects of aspect ratios, boundary conditions, Young’s modulus and density on frequency parameters are significant at lower value of the power law exponent. It has also been noted from present investigation that Pasternak foundation modulus has greater effect on frequency parameters as compared to the Winkler foundation modulus. Most of the results presented in this paper are novel and may be used for the validation purpose by researchers. Three dimensional mode shapes for the functionally graded plate resting on elastic foundation have also been presented in this article.

Circumferential waves in pre-stressed functionally graded cylindrical curved plates

2014 ◽  
Vol 21 (1) ◽  
pp. 87-97 ◽  
Author(s):  
Jiangong Yu ◽  
Chuanzeng Zhang ◽  
Xiaoming Zhang
Keyword(s):  
Initial Stress ◽  
Wave Equations ◽  
Axial Direction ◽  
Variable Coefficients ◽  
Functionally Graded ◽  
Initial Stresses ◽  
Polynomial Method ◽  
Coupled Wave Equations ◽  
Graded Material ◽  
Polynomial Series

AbstractInitial stress (pre-stress) in functionally graded material (FGM) structures is often inevitable because of the limitation of available manufacturing technology. On the basis of the “mechanics of incremental deformations”, the circumferential wave characteristics in FGM cylindrical curved plates under uniform initial stresses in the radial and axial directions are investigated. The Legendre polynomial series method is used to solve the coupled wave equations with variable coefficients. Through numerical examples, the convergence of the polynomial method is discussed. The influences of the initial stresses on the circumferential Lamb-like and the circumferential SH waves are investigated, respectively. Numerical results show that they are quite distinct. Moreover, the influences of the initial stress in the axial direction are very different from those in the radial direction, both on the dispersion curves and on the displacement and stress distributions.

scholarly journals Dynamic Analysis of Functionally Graded Timoshenko Beams in Thermal Environment Using a Higher-Order Hierarchical Beam Element

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Dinh Kien Nguyen ◽  
Van Tuyen Bui
Keyword(s):  
Dynamic Behaviour ◽  
Thermal Environment ◽  
Beam Element ◽  
Higher Order ◽  
Functionally Graded ◽  
Published Data ◽  
Timoshenko Beams ◽  
Material Inhomogeneity ◽  
Forced Vibration Analysis ◽  
Loading Parameter

A higher-order finite beam element for free and forced vibration analysis of functionally graded Timoshenko beams in thermal environment is formulated by using hierarchical functions to interpolate the kinematic variables. The shear strain is constrained to constant to improve the efficiency of the element. The effect of environmental temperature is taken into account in the element derivation by considering that the material properties are temperature-dependent and the temperature is nonlinear distribution in the beam thickness. The accuracy of the derived formulation is confirmed by comparing the results obtained in the present work with the published data. Numerical investigations show that the formulated element is efficient, and it is capable of giving accurate vibration characteristics by a small number of elements. A parametric study is carried out to highlight the effect of the material inhomogeneity, temperature rise, and loading parameter on the dynamic behaviour of the beams. The influence of the aspect ratio on the dynamic behaviour of the beam is also examined and highlighted.

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