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    Thin Film Thickness Measurement Using Colors of Interference Fringes

    , M.Sc. Thesis Sharif University of Technology Sadegh, Sanaz (Author) ; Amjadi, Ahmad (Supervisor)
    There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer  

    Study of mixed-convection heat transfer from an impinging jet to a solid wall using a finite-element method - Application to cooktop modeling

    , Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 46, Issue 4 , 2004 , Pages 387-397 ; 10407790 (ISSN) Karzar Jeddi, M ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
    The mixed-convection flow from a hot vertical impinging jet on a colder horizontal disc has been studied. The geometry is analogous to a conventional burning gas cooktop. A numerical simulation of the system has been carried out using the finite-element method to study the dependence of fluid flow and heat transfer on the geometric, thermal, and fluid flow parameters. Results show that heat transfer efficiency versus several parameters such as inlet velocity magnitude and flue gas temperature has an optimum value, in which heat transfer efficiency is maximum. With thermal conductivity of the solid wall, velocity angle, and solid wall diameter heat transfer efficiency has increasing behavior.... 

    In-service corrosion evaluation in pipelines using gamma radiography - A numerical approach

    , Article Insight: Non-Destructive Testing and Condition Monitoring ; Volume 46, Issue 7 , 2004 , Pages 396-398 ; 13542575 (ISSN) Edalati, K ; Rastkhah, N ; Kermani, A ; Seidi, M ; Movafeghi, A ; Sharif University of Technology
    Wall thickness measurement and deterioration determination of 6 and 10 inch pipes due to corrosion/erosion/pitting was evaluated by using radiographic film density measurements. Special reference blocks were prepared with defined step wall reductions and artificial defects. Gamma radiography with a Ir-192 source was used. A double-wall technique with longitudinal film arrangement was used for this purpose. Formulae were developed from the experiments for numerical calculations. It was observed that this method can determine remaining wall thickness as well as pitting corrosion in insulated and non-insulated pipes with differential and absolute density measurements. The purpose of the work... 

    Spray characteristics of a liquid-liquid coaxial swirl atomizer at different mass flow rates

    , Article Aerospace Science and Technology ; Volume 9, Issue 7 , 2005 , Pages 592-604 ; 12709638 (ISSN) Soltani, M. R ; Ghorbanian, K ; Ashjaee, M ; Morad, M. R ; Sharif University of Technology
    An experimental investigation is performed to explore the characteristics of sprays produced by a liquid-liquid coaxial swirl injector in a non-combusting environment. Phase Doppler anemometry is used for the measurement of velocity and Sauter Mean Diameter of droplets across and along the injection axis for various inner- and outer mass flow rates. Results of the combined spray are compared with those of inner- and/or outer spray alone. The results indicate that the inner injector has a larger influence on the flow field of the combined spray compared to the outer one. Further, the maximum velocity of the combined spray is close to the center of the spray thickness and the velocity... 

    Design and Implementation of a Fixed Distance to Object Imaging System using a 3-DOF. Table, with Integrated Software System for Acquisition, Processing and Display of Signals

    , M.Sc. Thesis Sharif University of Technology Karimi, Fateme (Author) ; Ravanbod, Hossein (Supervisor)
    Deriving the shape, area, volume, and orientation of a defect from the ultrasonic nondestructive testing images of the oil pipelines, paves the way for the estimation of its severity. This paper describes the design and implementation of an automatic structure which can move an ultrasonic probe over the surface of a test sample, while preserving the distance, i.e. stand-off, between them, whatever the shape of the surface might be. The fixed stand-off is implemented, closing a feedback loop with a distance meter sensor. Also an integrated software environment is developed for the control of the table, data acquisition, data processing and displaying the results. After acquiring the... 

    A strain gradient based yield criterion

    , Article International Journal of Engineering Science ; Vol. 77 , 2014 , pp. 45-54 ; ISSN: 00207225 Rahaeifard, M ; Ahmadian, M. T ; Firoozbakhsh, K ; Sharif University of Technology
    The classical yield criteria do not describe the yield size-dependency that has been observed in micro-scale structures (Fleck, Muller, Ashby, & Hutchinson, 1994; Stolken and Evans 1998; Moreau et al. 2005), and may also significantly underestimate the yield loads of structures at micron and sub-micron scales (Son, Jeong, & Kwon, 2003; Liu et al., 2013). The present paper suggests a specific size-dependent yield criterion based on the strain gradient theory that is aimed at addressing this inadequacy. In order to develop the strain gradient based yield criterion, the deviatoric part of the strain energy is calculated based on this theory and equated to the deviatoric strain energy of a... 

    Tractive rolling contact mechanics of graded coatings

    , Article International Journal of Solids and Structures ; Volume 49, Issue 6 , March , 2012 , Pages 929-945 ; 00207683 (ISSN) Guler, M. A ; Adibnazari, S ; Alinia, Y ; Sharif University of Technology
    In this study, the tractive rolling contact problem between a rigid cylinder and a graded coating is investigated. The main objective of this study is to investigate the effect of the stiffness ratio, the coefficient of friction and the coating thickness on the surface contact tractions, the surface in-plane stress, the stick zone length and the creep ratio parameter that may have a bearing on the fatigue life of the component. Assuming that the shear modulus varies exponentially through the thickness of the coating, the governing integral equations associated with the rolling contact problem are constructed. Furthermore, it is supposed that the contact patch is controlled by a central stick... 

    Determination of the scattered fields of an SH-wave by an eccentric coating-fiber ensemble using DEIM

    , Article International Journal of Engineering Science ; Volume 46, Issue 11 , 2008 , Pages 1136-1146 ; 00207225 (ISSN) Sarvestani, A. S ; Mohammadi Shodja, H ; Delfani, M. R ; Sharif University of Technology
    To date, the existing theories pertinent to the determination of the scattered fields of an inhomogeneity have been limited to certain topological symmetries for which the method of wave-function expansion is widely used. In the literature the wave-function expansion method has also been employed to the case involving concentric coated fiber. An alternative approach is the dynamic equivalent inclusion method (DEIM) proposed by Fu and Mura [L.S. Fu, T. Mura, The determination of elastodynamic fields of an ellipsoidal inhomogeneity. ASME J. Appl. Mech. 50 (1983) 390-396.] who found the scattered field of a single spheroidal inhomogeneity. The pioneering work of Eshelby [J.D. Eshelby, The... 

    Free vibration analysis of functionally graded cylindrical shells including thermal effects

    , Article Thin-Walled Structures ; Volume 45, Issue 6 , 2007 , Pages 591-599 ; 02638231 (ISSN) Haddadpour, H ; Mahmoudkhani, S ; Navazi, H. M ; Sharif University of Technology
    Free vibration analysis of simply supported FG cylindrical shells for four sets of in-plane boundary conditions is performed. The material properties are assumed to be temperature-dependant and gradually changed in the thickness direction of the shell. The effects of temperature rise are investigated by specifying arbitrary high temperature on the outer surface and the ambient temperature on the inner surface of the cylinder. Distribution of temperature across the shell thickness is found from steady state heat conduction only in the thickness direction. The equations of motion are based on Love's shell theory and the von Karman-Donnell-type of kinematic nonlinearity. The static analysis is... 

    Velocity distributions in (r,θ) directions for laminar flow of a film around horizontal circular tube

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Abyaneh, M. H. J ; Saidi, M. H ; Sharif University of Technology
    Velocity distributions in (r,θ) directions are evaluated by solving simultaneous simplified Navier-Stokes equations (NSE) and continuity equation (CE) in polar coordinate. The analysis is based on steady state laminar flow of thin falling liquid film on a horizontal circular tube, for cases in which traction on the film surface is considered negligible. It is a common geometry for part of engineering problems such as evaporator, condenser, absorber, generator of absorption chillers and other similar units in mechanical and chemical engineering. Knowledge of the velocity profiles is usually needed for: 1- solving governing energy and species equations 2- estimating the average and film... 

    An experimental investigation on the deformation behavior during wire flat rolling process

    , Article Journal of Materials Processing Technology ; Volume 160, Issue 3 , 2005 , Pages 313-320 ; 09240136 (ISSN) Kazeminezhad, M ; Karimi Taheri, A ; Sharif University of Technology
    In the present study a laboratory flat rolling machine is utilized to assess the deformation behavior of low and high carbon steel wires in wire flat rolling process. The effects of friction coefficient, rolling reduction and roll speed on rolling force and deformation behavior of the wires are experimentally investigated. It is found that the roll speed affects considerably the rolling force but a negligible effect on deformation behavior. It is noted that by increasing the roll speed, the rolling force may decrease or increase depending on the magnitude of the roll speed. Also, the deformation behavior of the wires in flat rolling is formulated. A relationship is developed for calculating... 

    On the rolling contact problem of two elastic solids with graded coatings

    , Article International Journal of Mechanical Sciences ; Volume 64, Issue 1 , 2012 , Pages 62-81 ; 00207403 (ISSN) Guler, M. A ; Alinia, Y ; Adibnazari, S ; Sharif University of Technology
    In this study, the rolling contact problem of two elastically similar cylinders coated with functionally graded materials is investigated. The singular integral equations approach is utilized to extract the governing equations of the problem. The governing equations are discretized into systems of algebraic equations by virtue of the Gauss-Chebyshev integration method. Comprehensive parametric study is performed to examine the effects of mechanical properties, coating thickness and external loads on the surface stress components, stick/slip transition, creep ratio and power loss. This study aimed to emphasize the capability of graded materials in improving the rolling contact fatigue of... 

    Enhanced hardness and corrosion resistance of Zn/SiO2 films by electrodeposition

    , Article Journal of the Electrochemical Society ; Volume 162, Issue 9 , 2015 , Pages D480-D485 ; 00134651 (ISSN) Ghorbani, M ; Salehi, F ; Razavizadeh, O ; Sharif University of Technology
    Electrochemical Society Inc  2015
    The electrodeposition of Zn-SiO2 nanocomposites has been investigated with different electrolytes: triethanolamine as a dispersing agent, and cetyl trimethylammonium bromide and dodecyl dimethylamine oxide as ionic (cationic) and non-ionic surfactants. Appropriate electrophoretic potentials for each solution were obtained using cyclic voltammetry. The results show that the most stable SiO2 nanoparticles with zeta potential range of 25 to 41 mV, along with highest SiO2 mobility of 0.4 to 0.7 m2/V.s were dispersed by triethanolamine in ethanol and the resulting coating adhesion improved up to 5.87 MPa in the standard pull off test, with the enhanced hardness of... 

    The scattering of P-waves by a piezoelectric particle with FGPM interfacial layers in a polymer matrix

    , Article International Journal of Solids and Structures ; Volume 47, Issue 18-19 , 2010 , Pages 2390-2397 ; 00207683 (ISSN) Kamali, M. T ; Shodja, H. M ; Sharif University of Technology
    Propagation of P-wave in an unbounded elastic polymer medium which contains a set of nested concentric spherical piezoelectric inhomogeneities is formulated. The polymer matrix is made of Epoxy and is isotropic; each phase of the inhomogeneity is made of a different piezoelectric material and is radially polarized and has spherical isotropy. Note that the individual phases are homogeneous, and all interfaces are perfectly bonded. The scattered displacement and electric potentials in the matrix are expressed in terms of spherical wave vector functions and Legendre functions, respectively. The transmitted displacement and electric potentials within each phase of the piezoelectric particle are... 

    Mechanism of Al-Si codeposition on In738LC through single-step diffusion process

    , Article International Journal of Surface Science and Engineering ; Volume 11, Issue 1 , 2017 , Pages 1-11 ; 1749785X (ISSN) Nikzad, S ; Abdi, M ; Rastegari, S ; Sharif University of Technology
    The out-of-pack cementation method was applied to coat the Nickel-based super alloy IN738LC with Si-modified aluminide. Different mixtures of the pack containing pure Al, Si, alumina powders as an inert filler, and NH4Cl as a halide salt activator were used for co-deposition at 950 and 1,050°C. The results showed although the amount of subhalide vapour pressures of Al and Si were equal at 1,050°C, Al atoms diffused only after Si atoms had been deposited. Before heat treatment, the coating thickness formed by the pack containing 2.3 wt.% Al was 6 μm more than that containing 3.5 wt.% Al. After heat treatment, thickening coatings formed within the pack containing 2.3 wt.% Al was less than that... 

    Stress intensity factors of multiple axisymmetric interface cracks in an isotropic layer with FGM coating under torsional loading

    , Article Multidiscipline Modeling in Materials and Structures ; Volume 15, Issue 6 , 2019 , Pages 1352-1365 ; 15736105 (ISSN) Tavakoli, A ; Pourseifi, M ; Rezaei, S ; Sharif University of Technology
    Emerald Group Publishing Ltd  2019
    Purpose: The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and its functionally graded material (FGM) coating under torsional loading. Design/methodology/approach: In this paper, the authors employ the distributed dislocation technique to the stress analysis, an FGM coating-substrate system under torsional loading with multiple axisymmetric cracks consist of annular and penny-shaped cracks. First, with the aid of the Hankel transform, the stress fields in the homogeneous layer and its FGM coating are obtained. The problem is then reduced to a set of singular integral equations... 

    A finite element formulation for analysis of functionally graded plates and shells

    , Article Archive of Applied Mechanics ; Volume 74, Issue 5-6 , 2005 , Pages 375-386 ; 09391533 (ISSN) Naghdabadi, R ; Hosseini Kordkheili, S. A ; Sharif University of Technology
    A finite element formulation is derived for the thermoelastic analysis of functionally graded (FG) plates and shells. The power-law distribution model is assumed for the composition of the constituent materials in the thickness direction. The procedure adopted to derive the finite element formulation contains the analytical through-the-thickness integration inherently. Such formulation accounts for the large gradient of the material properties of FG plates and shells through the thickness without using the Gauss points in the thickness direction. The explicit through-the-thickness integration becomes possible due to the proper decomposition of the material properties into the product of a... 

    Optimization of air plasma sprayed thermal barrier coating parameters in diesel engine applications

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3530-3538 ; 10599495 (ISSN) Azadi, M ; Farrahi, G. H ; Moridi, A ; Sharif University of Technology
    In the present paper, an optimization of thermal barrier coating parameters is performed for diesel engine applications. The substrate is A356.0-T7, a cast aluminum alloy which has a vast application in diesel engines, and the alloy is coated by plasma sprayed ZrO2-8 wt.% Y2O3. Parameters including the feed rate of coating powders, the nozzle distance to specimen surfaces, and the coating thickness are optimized by thermal shock fatigue tests and bending tests. Optimum values of the feed rate and the nozzle distance are 30 g/min and 80 mm, respectively, when the objective is considered as maximizing the bending strength. Thermal shock tests demonstrate that lower thickness of coating layers... 

    Investigations of the failure in boilers economizer tubes used in power plants

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 9 , 2013 , Pages 2691-2697 ; 10599495 (ISSN) Moakhar, R. S ; Mehdipour, M ; Ghorbani, M ; Mohebali, M ; Koohbor, B ; Sharif University of Technology
    In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO4) and Iron hydroxide sulfate (FeOH(SO4)) phases formed on the steel surface. A considerable amount of Sulfur was also... 

    Corrosion behavior of ZrO2-SiO2-Al2O3 refractories in lead silicate glass melts

    , Article Journal of the European Ceramic Society ; Volume 31, Issue 5 , 2011 , Pages 715-721 ; 09552219 (ISSN) Rahimi, R. A ; Ahmadi, A ; Kakooei, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    High-temperature (1200-1350°C) corrosion of fused-cast ZrO2-Al2O3-SiO2 (ZAS) refractory contacting lead silicate glass melt (LSG) containing 68.5wt% PbO was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), x-ray diffraction (XRD), thickness measurement and Archimedes density measurement. ZAS durability was improved by baddeliyete content and deteriorated with open porosity proportion, corundum percentage and eutectic mixture presence. Diffusion of lead resulted in fusion-temperature lowering of the glassy layers embedded within the ZAS particles. Heating caused viscosity drop across the interface, loosening the...