Although the number and the severity of TBC applications on hot section components have dramatically increased in the past decade, premature spallation failure of TBCs, due to mismatch of thermal expansion at the metal/ceramic interface of the two coating layers, during service is still an overriding concern. Therefore, Functionally Graded Materials ((FGM)s) with a gradual compositional variation have been introduced. In this study, comparison of properties of two different types of thermal barrier coatings (TBCs) was made to improve the surface characteristics on high temperature components. These TBCs consisted of a duplex TBC and a five layered Functionally Graded TBC. In both coatings, Yittria partially stabilized Zirconia topcoat (YSZ) was deposited by air plasma spraying (APS) and NiCrAlY bond coat was deposited by high velocity oxyfuel spraying (HVOF). In (FGM) coating, Functionally Graded layer was sprayed by air plasma process by varying the feeding ratio of YSZ/NiCrAlY powders using two separate powder feeders. Then, isothermal oxidation was carried out at 950oC in atmosphere to obtain the plot of mass change vs. time to study oxidation kinetic. Micro structural and compositional changes of coating, oxides formed during service were examined by optical microscope and SEM with EDS. (FGM) coating failed after 2100 h and duplex coating failed after 1700 h. Finally, it was found that (FGM) coating is more qualified than duplex TBC and stands for a longer time.

Functionally Graded Materials are the novel class of advanced composite structures with variable properties in one or more directions. The mechanical properties of Functionally Graded Materials ((FGM)) such as Poisson’s ratio, Young’s modulus of elasticity, material density and shear modulus of elasticity undergo changes gradually and continuously between two surfaces in a predetermined manner. (FGM) structures are often made of a combination of ceramics and metals in which the metal component provides strength and fracture resistance while ceramic component provides thermal resistance. Due to desirable properties, (FGM) Materials are used in various fields of engineering such as optics, electronics, space vehicles, shipbuilding, mechanical, biomechanical and other engineering structures subjected to high thermal and residual stresses. Therefore, the analytical study of thermoelastodynamic problems is of great importance for the Functionally Graded media. The use of potential functions to analyze three-dimensional elastic problems is one of the most effective methods. This method facilitates solving three-dimensional elastic problems by uncoupling the set of governing differential equations or at least simplifying them. In the present study, the displacement potential functions for solving thermoelastodynamic problems in the transversely isotropic media with Functionally Graded Materials are introduced. For this purpose, first, the three-dimensional kinematic and thermodynamic equations for the Functionally Graded Materials in the transversely isotropic Materials are written and then using a systematic method to separate the equations, the displacement potential functions to solve thermoelastodynamic problems are obtained, which can be used further to solve problems of beams, plates, shells, and infinite and semi-infinite media. The obtained potential functions include two scalar functions F and χ; the scalar function F satisfies the sixth-order partial differential equation while the χ-scalar function satisfies the second-order partial differential equation. In addition, in the present study, the thermal potential functions for the specific state of the isotropic Functional Graded media are presented.

In this paper time-dependent creep evolution analysis of thick-walled rotating (FGM) cylinders made of Al-SiC composite has been carried out, using method of successive elastic solution. The material creep constitutive model has been described by Norton’ s law, considering the experimental results of Pandey on Al-SiC composite. All mechanical and thermal properties except Poisson’ s ratio are radial dependent, based on the volume content of SiC reinforcement. Loading is composed of an inertia body force due to rotation and a distributed temperature field because of steady state heat conduction from the inner to the outer surface of the cylinder. It has been found that the volume-content distribution of SiC reinforcement has a significant effect on initial elastic stress distribution. It has been concluded that radial stresses are increasing with time during creep evolution, while circumferential and effective stresses become more uniform, due to stress redistribution and finally the solution converges to stationary stresses, displacement and strains almost after fifty years.

In previous researches, mechanical behavior of a microgripper with homogenous and the same material has been studied. In this paper considering the desired characteristics of (FGM)s, as a good thermal and wear resistance, the mechanical behavior of (FGM) microgripper under DC voltage and temperature variations is investigated. It is assumed that the two microbeams of the (FGM) microgripper are mounted symmetrically against each other and one side of the microbeams is made of a pure metal the other side is a mixture of metal and ceramic, and the percentage of ceramic varies exponentially through the microbeams thickness. The nonlinear equations governing the static deflection of microbeams due to the application of DC voltage and the temperature changes are derived and solved using the step by step linearization method and the Galerkin method. The response and the stability of the system against the variation of DC voltage and temperature are investigated. Also, the effect of geometrical dimensions, ceramic percentage and its variations through the microbeams thickness on the mechanical behavior and the system stability are studied.

Perforated discs have many applications in different parts of industry. By making such disks of Functionally Graded Materials, more capabilities can be obtained from them. Vibration analysis of these kinds of disks can help us make them more efficient. In this paper, modeling and evaluation of disk vibration of Functionally Graded Materials with regard to thickness were carried out using Abaqus software. Since no certain element has been defined regarding Functionally Graded Materials for the design and analysis of a particular element in Abaqus software, molding of such Materials has been used in this application. In order to verify the results, the results obtained from ABAQUS analysis have been compared with those available in the literature. The obtained results show that by defining more layers with regard to changes in properties, the obtained results approach the exact solutions.

In this research, the free vibration of rotating tapered Timoshenko beam with piezoelectric layer has been studied. It is assumed that the beam is made of Functionally Graded Materials ((FGM)) through the thickness direction and the boundary condition is a cantilever attached to the hub. The first-order shear deformation theory has been used to drive governing equations. At first, the total energy of the system such as potential and kinetic energies for the beam and piezoelectric layer has been derived, and then the natural frequencies of the beam have been determined by the Ritz approach based on minimizing the total system energy. After verifying the results by comparing them with other research, the effects of some parameters such as hub radius, rotational speed, taper ratios, rotary inertia, material gradient, piezoelectric voltage, and beam thickness on the natural frequencies of the tapered Timoshenko beam have been studied in detail. The results showed that with increasing the angular velocity of the beam, the natural frequency increases so that as the increasing velocity increases, the natural frequency increases with a steeper slope.