Topic
Functionally graded material
About: Functionally graded material is a research topic. Over the lifetime, 4250 publications have been published within this topic receiving 99610 citations.
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01 Jan 2012
TL;DR: In this paper, a tip-specimen configuration and its associated localized effects has been used to rapidly produce highly consolidate regions in addition to functionally graded porous materials on the micro-scale under a continuous current mode.
Abstract: Spark Plasma Sintering (SPS) is a process that has stimulated worldwide interest for the rapid consolidation of powder-based materials where electric current has played a major role. In this dissertation, the localization of SPS through current activated tip-based sintering (CATS) is presented where electric current is selectively applied to small targeted regions of a green compact/powder bed via a precision controlled electrically conductive small tip. The unique tip-specimen geometry allows for locally controlled temperature and current distributions that can result in microstructural modifications on the micro-scale. A novel experimental setup was used to investigate the spatial and temporal temperature evolution in CATS under continuous electric current exposure. Both tip and compact surface temperatures were found to be a function of current exposure time, particle size and green compact density. The concept of effective current density is introduced to explain the findings in addition to the role of electrical and thermal conductivities. A finite element model was developed revealing surface and subsurface temperature profiles in CATS, which were supported by experimental findings. The unique tip-specimen configuration in CATS and its associated localized effects has been used to rapidly produce highly consolidate regions in addition to functionally graded porous materials on the micro-scale under a continuous current mode. The effects of initial green density and particle size on the porosity profile and pore size distribution in the developed micro-scale functionally graded material are discussed. The use of micro-scale tips (10 & 50 [mu]m) in a moving tip configuration was established using a novel micro-CATs machine, where the effects of tip speed and current intensity were studied on nickel and copper powders with varying initial green density and particle size (down to 500nm). The precision controlled movement of the tips under current exposure enabled the consolidation of the material in remarkably thin regions (<5 [mu]m) enabling micro-scale processing. Slower tip speeds at higher current intensities produced the highest degree of consolidation. Smaller particle sizes and higher initial green density powder compacts tend to experience higher quality consolidated lines due to a smaller inter-particle spacing
TL;DR: In this article, the authors investigated the behavior of shell vibration based on different parameters of geometrical material, such as nickel, stainless steel, zirconia, and alumina.
Abstract: Cylindrical shells play an important role for the construction of functionally graded materials (FGMs). Functionally graded materials are valuable in order to develop durable materials. They are made of two or more materials such as nickel, stainless steel, zirconia, and alumina. They are extremely beneficial for the manufacturing of structural elements. Functionally graded materials are broadly used in several fields such as chemistry, biomedicine, optics, and electronics. In the present research, vibrations of natural frequencies are investigated for different layered cylindrical shells, those constructed from FGMs. The behavior of shell vibration is based on different parameters of geometrical material. The problem of the shell is expressed from the constitutive relations of strain and stress with displacement, as well as it is adopted from Love’s shell theory. Vibrations of natural frequencies (NFs) are calculated for simply supported-simply supported (SS-SS) and clamped-free (C-F) edge conditions. The Rayleigh–Ritz technique is employed to obtain the shell frequency equation. The shell equation is solved by MATLAB software.
TL;DR: In this article, a rapid calculation procedure for the analysis of a functionally graded tube subjected to internal pressure under plane strain condition is presented, which is based on an approximation of variation of modulus of elasticity by an integral average value.
Abstract: A rapid calculation procedure is presented for the analysis of a functionally graded tube subjected to internal pressure under plane strain condition. The exact analysis for the problem involves derivation of a hyper-geometric differential equation whose solution is a hyper-geometric function. The exact analysis involves the use of complicated terms and is time-consuming. In order to simplify the calculations, a procedure based on an approximation of variation of modulus of elasticity by an integral average value has been studied which resulted in faster calculation and results obtained have been in close agreement with exact solution highlighting the effect of material properties on stresses.
Journal Article•
TL;DR: In this article, the authors present a thermo-elastic analysis for functionally graded thick-walled cylinder with temperature dependent material properties at steady condition, where the length of cylinder is infinite and loading is consist of internal hydrostatic pressure and temperature gradient.
Abstract: In this work, thermo – elastic analysis for functionally graded thick – walled cylinder with temperature - dependent material properties at steady condition is carried out. The length of cylinder is infinite and loading is consist of internal hydrostatic pressure and temperature gradient. All of physical and mechanical properties expect the Poisson's ratio are considered as multiplied an exponential function of temperature and power function of radius. With these assumptions, the nonlinear differential equations for temperature distribution at cylindrical coordinate is obtained. Temperature distribution is achieved by solving this equation using classical perturbation method. With considering strain – displacement, stress – strain and equilibrium relations and temperature distribution that producted pervious, the constitutive differential equation for cylinder is obtained. By employing mechanical boundary condition the radial displacement is yield. With having radial displacement, stresses distribution along the thickness are achieved. The results of this work show that by increasing the order of temperature perturbation series the convergence at curves is occurred and also dimensionless radial stress decrease and other stresses with dimensionless radial displacement increase.
TL;DR: In this paper, the authors considered the square root of area parameter to evaluate arbitrary shaped defects or cracks in the vicinity of an interface, where "area" is the projected area of the defect or crack.
Abstract: In this study, stress intensity formulas are considered in terms of the square root of area parameter to evaluate arbitrary shaped defects or cracks in the vicinity of an interface. Here “area” is the projected area of the defect or crack. Stress intensity factors for an elliptical crack parallel to a bimaterial interface are considered with varying the distance, aspect ratio of the crack, and combinations of material's elastic constants. Also, stress intensity factors of an interface crack and a crack in a functionally graded material are investigated. Then, it is found that the maximum stress intensity factors normalized by the square root of area are always insensitive to the crack aspect ratio. They are given in a form of formulas useful for engineering applications.