Linear And Nonlinear Thermoelastic Analysis Of Functionally Graded Materials Axisymmetric Rotating Disks

Functionally graded materials (FGMs) are non-homogeneous materials where the volume fraction of two or more materials is varied, as a power-law distribution, continuously as a function of position along certain dimension(s) of the structure. FGMs are usually made of a mixture of ceramic and metals. The ceramic constituent of the material provides the high temperature resistance due to its low thermal conductivity and the ductile metal constituent, on the other hand, prevents fracture caused by stress due to high temperature gradient in a very short period of time. These materials, usually designed to operate in high temperature environments, find their applications in automotive and aerospace as turbine rotors, flywheels, gears, tubes, disk brakes and energy storage devices. In all these applications, the performance of the components in terms of efficiency, service life and power transmission capacity depends on the material, thickness profile, speed of rotation and operating conditions. Normally, these components are fabricated by using homogeneous metal. In the present work, components made of FGM are to be considered and they are axisymmetric disks subjected to body force, bending and thermal loads. The displacement and stress fields of these components are determined both analytically and numerically. The effect of geometry and material-property nonlinearity on small and large deflections in functionally graded rotating disks is investigated by studying their elastic behavior under thermo mechanical loads. Six types of thickness profiles, namely uniform, linear, concave, convex, hyperbolic convergent and hyperbolic divergent are considered. Material properties such as Young’s modulus,, mass density,hEρ, and the thermal conductivity,α,are assumed to be represented by two power law distributions along the radial direction. Material properties are also assumed to be temperature-dependent for more accurate and realistic results. A theoretical formulation for bending analysis of functionally graded (FG) rotating disks based on First Order Shear Deformation Theory (FSDT) is presented. A semi analytical solution for displacement field is obtained. New linear and nonlinear equilibrium equations for FG axisymmetric rotating disk with bending and thermal loading are developed and presented. The disk has material properties varying through the thickness of the disk graded according to a power-law distribution of the volume fraction of the constituents. FSDT and von Karman theory are used and both small and large deflections are considered. In the case of small deflection, an exact solution for displacement field is given. For large deflection, power series solutions are employed to solve for displacement field. The results for displacement and stresses are normalized with respect to the corresponding disk with homogeneous material geometry and certain value of properties of disk with the same unit respectively. All the results shown are thus independent of the physical dimension of the component. As for practical applications, rotating disks with typical dimensions up to 2 meter diameter are considered. The results for free-free FG rotating disk show that there exist combinations of values of parameters related to thickness profiles for which the radial stress can attain its maximum at radial distance greater than half of the radius, to be more specific at if the ratio of inner to outer radius is assumed to be 0.2, and also the ratio of thickness to outer radius is 0.2 while material properties change in radial direction. The results for FG disk with variable thickness under thermomechanical loading show that an efficient and optimal design of the disk requires variable section thicker at the hub and tapering to smaller thickness at the periphery and also that the temperature-dependent material properties must be considered in high temperature environment. Applying FSDT, while material properties change in radial direction, it is seen that for the specific value of the grading index n(), the moment resultants in a FG solid disk with convex or constant thickness profile are lower throughout than those in pure material disk. In case of changing material properties in thickness direction by using large deflection theory, it is observed that the radial stresses in a full-metal disk due to thermal load, body force and vertical pressure are smaller than those in a full-ceramic disk. It is found that the small deflection theory gives large errors in the results for FG disks if the ratio of maximum deflection to thickness is close to 0.4 for a homogeneous (full-ceramic in this study) disk

New stable phosphorus ylide (p-tolyl)(3)P = CHCOC6H4 (p-CN) and its metal complexes : crystal and molecular structure, theoretical study and antibacterial investigation

A new stable phosphorus ylide (p-tolyl)(3)P = CHCOC6H4(p-CN) (Y) was synthesized and a series of novel complexes based on metalated phosphorus ylides were prepared through the reaction of (p-tolyl)(3)P = CHCOC6H4(p-CN) with mercury(II) halides, AgNO3 and Cd(NO3)(2) in equimolar ratios using MeOH or CH2Cl2 as solvent. Characterization of the obtained compounds was also performed by elemental analysis, FT-IR, H-1, P-31, and C-13 NMR techniques. The crystal structure of complex [Y -> HgCl2] was determined by X-ray diffraction method, in which the coordination of the prepared ylide occurred to the Hg center in a symmetric halide-bridged structure. The structure and nature of Hg-C bond in the aforementioned complex were studied based on DFT method using Natural bond orbital (NBO), Energy-decomposition analysis (EDA) and ETS-NOCV. The antibacterial applicability of the synthesized mercury(II) complexes was explored against five Gram-positive and four Gram-negative bacteria types. The novelty of the presented work is: (1) the synthesis of five new complexes, (2) conducting theoretical and (3) biological investigation of the prepared complexes

Paradoxical Embolism in a Patient with Patent Foramen Ovale; a Case Report

Patent foramen ovale (PFO) is usually asymptomatic; however, it could be quite dangerous for patients with right side clot in which thrombus can transmit the PFO and paradoxically emboli to systemic circulation. Here we present a patient with ankle fracture and paradoxical embolus to the brain, who was successfully treated with emergent thrombectomy, inferior vena cava (IVC) filter placement and anticoagulation therapy. Despite the high rate of mortality in these patients, fortunately our patient survived with surgical treatment

Auto adjust masses of automotive structures with desired centre of gravity

In this study a subroutine was developed and added in the pre-processing module of the frame work of commercial package of ANSYS to distribute the extra masses according to specific assigned centre of gravity (COG). The work further calculate the first bending and torsional natural frequencies of the simplified body in white (BIW) model of automotive in order to maximize these frequencies with final mass constraint. It is found that adding the extra masses symmetrically about longitudinal axis helps to improve the first bending and torsion natural frequencies. However, removing the mass along this axis leads to have higher values in the case of first bending and natural frequencies

Synthesis and characterization of a heptadentate (N4O3) schiff base ligand and associated La(ІІІ), Sm(III) AND Gd(III) complexes, and a theoretical study

A new symmetrical potentially heptadentate (N4O3) Schiff base ligand    {N[CH2CH2CH2N=CH(2-OH-5-BrC6H3)]3} (H3L6) and associated neutral Gd(III), La(III) and Sm(III) complexes, were synthesized. The new compounds were characterized by IR spectroscopy, elemental analysis and mass spectrometry in all cases and in the case of ligand also with NMR spectroscopy. The relative capability of H3L6 to encapsulate a lanthanide ion, herein La(III), has been theoretically studied by ab initio restricted Hartree-Fock (RHF) and DFT (B3LYP) methods. The calculation confirmed that the H3L6 ligand can effectively encapsulate a lanthanide ion and enforce a seven-coordinate geometry.KEY WORDS:Ab initio, Heptadentate ligands, Lanthanide ions, Schiff base complexesBull. Chem. Soc. Ethiop. 2010, 24(1), 59-66

Spectral, crystallographic, theoretical and antibacterial studies of palladium(II)/platinum(II) complexes with unsymmetric diphosphine ylides

The reaction of alpha-keto-stabilized diphosphine ylides [Ph2P(CH2)(n)PPh2C(H)C(O)C6H4-p-CN] (n = 1 (Y-1); n = 2 (Y-2)) with dibromo(1,5-cyclooctadiene) palladium(II)/platinum(II) complexes, [Pd/PtBr2(cod)], in equimolar ratio gave the new cyclometalated Pd(II) and Pt(II) complexes [Br2Pd(kappa(2)-Y-1)] (1), [Br2Pt(kappa(2)-Y-1)] (2), [Br2Pd(kappa(2)-Y-2)] (3) and [Br2Pt(kappa(2)-Y-2)] (4). These compounds were screened in a search for novel antibacterial agents and characterized successfully using Fourier transfer infrared and NMR (H-1, C-13 and P-31) spectroscopic methods. Also, the structures of complexes 1 and 2 were characterized using X-ray crystallography. The results showed that the P,C-chelated complexes 1 and 2 have structures consisting of five-membered rings, while 3 and 4 have six-membered rings, formed by coordination of the ligand through the phosphine group and the ylidic carbon atom to the metal centre. Also, a theoretical study of the structures of complexes 1-4 was conducted at the BP86/def2-SVP level of theory. The nature of metal-ligand bonds in the complexes was investigated using energy decomposition analyses (EDA) and extended transition state combined with natural orbitals for chemical valence analyses. The results of EDA confirmed that the main portions of Delta E-int, about 57-58%, in the complexes are allocated to Delta E-elstat

Bending analysis of a functionally graded rotating disk based on the first order shear deformation theory

The theoretical formulation for bending analysis of functionally graded (FG) rotating disks based on first order shear deformation theory (FSDT) is presented. The material properties of the disk are assumed to be graded in the radial direction by a power law distribution of volume fractions of the constituents. New set of equilibrium equations with small deflections are developed. A semi-analytical solution for displacement field is given under three types of boundary conditions applied for solid and annular disks. Results are verified with known results reported in the literature. Also, mechanical responses are compared between homogeneous and FG disks. It is found that the stress couple resultants in a FG solid disk are less than the stress resultants in full-ceramic and full-metal disk. It is observed that the vertical displacements for FG mounted disk with free condition at the outer surface do not occur between the vertical displacements of the full-metal and full-ceramic disk. More specifically, the vertical displacement in a FG mounted disk with free condition at the outer surface can even be greater than vertical displacement in a full-metal disk. It can be concluded from this work that the gradation of the constitutive components is a significant parameter that can influence the mechanical responses of FG disks

Transient and thermal contact analysis for the elastic behavior of functionally graded brake disks due to mechanical and thermal loads

In this paper, the transient and contact analysis of functionally graded (FG) brake disk is presented. The analysis was carried out using ANSYS parametric design language (APDL). The FG brake disk is made of metal–ceramic material. The material properties vary in radial direction with the values from full-metal at the inner radius to that of full-ceramic at the outer radius. In the analysis, FG brake disk is in contact with one pure pad disk and coulomb contact friction is considered as heat source. The non-dimensional results are obtained for specific value of grading index (n = 1) by considering different material property divisions of 25, 50, 100 and 200. The results presented are for the pressure distribution, total stress, pad penetration, friction stress, heat flux and temperature during contact, for different values of contact stiffness factor, Fkn, which depends on the property gradation of FG brake disk with 200 material property divisions. The results show that the contact pressure and contact total stress increase with increasing values of Fkn, and hence it can be concluded that gradation of the metal–ceramic has significant effect in the thermomechanical response of FG brake disks

Finite element analysis of thermoelastic contact problem in functionally graded axisymmetric brake disks

An analysis of thermoelastic contact problem of functionally graded (FG) rotating brake disk with heat source due to contact friction is presented. Finite element method (FEM) is used. The material properties of disk are assumed to be represented by power-law distributions in the radial direction. The inner and outer surfaces considered are metal and ceramic, respectively. Pure material is considered for the brake pad. Coulomb contact friction is assumed as the heat source. It is divided into two equal parts between pad and brake disk which leads to thermal stresses. Mechanical response of FG disks are compared and verified with the known results from the literatures. The results show that the maximum value of radial displacement in mounted FG brake disk is not at outer surface. It is found that the all areas between pad and brake disk is in full-contact status when the ratio of pad thickness to brake disk thickness is 0.66. It is observed that the total strain due to thermomechanical load is negative for some parts of the disks, whereas, the thermal strains are always positive. It can be concluded that gradation index of the metal-ceramic has significant effect in the thermomechanical response of FG disks