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    Cosintering of powder injection molding parts made from ultrafine WC-Co and 316L stainless steel powders for fabrication of novel composite structures

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1, January 2010, Pages 233-241 Simchi, A. (Abdolreza) ; Petzoldt, F ; Sharif University of Technology
    Abstract
    Abstract Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (> 4 pct) is developed in the temperature range of 1080° C to 1350° C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the  

    The gas-oil interfacial behavior during gas injection into an asphaltenic oil reservoir

    , Article Journal of Chemical and Engineering Data ; Volume 58, Issue 9 , 2013 , Pages 2513-2526 ; 00219568 (ISSN) Escrochi, M ; Mehranbod, N ; Ayatollahi, S ; Sharif University of Technology
    2013
    Abstract
    Oil displacement and recovery efficiency during gas injection depends on the competition between driving forces and capillary resistance that is governed by gas-oil interfacial behavior. Detailed study of the interfacial forces during gas injection is the main objective of this research work. The effects of injecting gas composition and the possibility of asphaltene precipitation in a wide pressure range were determined through comprehensive experimental study. This was performed by measurement of interfacial tension of a highly asphaltenic Iranian crude oil in three surrounding gas mediums. The results showed that as pressure increases, the rate to reach miscibility reduces in the vicinity... 

    Microstructure and mechanical properties of MoSi2-MoSi2 joints brazed by Ag-Cu-Zr interlayer

    , Article Materials and Design ; Volume 49 , August , 2013 , Pages 197-202 ; 02613069 (ISSN) Hatami Ramsheh, H ; Faghihi Sani, M. A ; Kokabi, A. H ; Sharif University of Technology
    Elsevier Ltd  2013
    Abstract
    The present work investigates joining of two MoSi2 parts through Cusil/Zr/Cusil interlayer with Cusil being a commercial eutectic of Cu-Ag alloy. The joining operation was implemented in an inert gas tube furnace by brazing. The brazing temperature ranged from 800 to 930°C while the operation lasted for 60min. Evaluation of joints strength through shear loading identified the maximum strength 60.31MPa for the brazed sample at 830°C. Interfacial microstructure was studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) techniques. Applying the temperature of 830°C was led to a uniform dense joint consisting of various phases with... 

    Numerical simulation of laminar and turbulent two-phase flow in pressure-swirl atomizers

    , Article AIAA Journal ; Volume 50, Issue 10 , 2012 , Pages 2091-2101 ; 00011452 (ISSN) Nouri Borujerdi, A ; Kebriaee, A ; Sharif University of Technology
    AIAA  2012
    Abstract
    This paper has developed an axisymmetric laminar and turbulent two-phase flow solver to simulate pressure-swirl atomizers. Equations include the explicit algebraic Reynolds stress model, the Reynolds-averaged Navier-Stokes, and the level set equation. Applying a high-order compact upwind finite difference scheme with the level set equation being culminated to capture the interface between air-liquid two-phase flow and decreasing the mass conservation error in the level set equation. The results show that some recirculation zones are observed close to the wall in the swirl chamber and to the axis. This model can predict converting the Rankin vortex in the swirl chamber to the forced vortex in... 

    Mixed protein-surfactant adsorption layers formed in a sequential and simultaneous way at water-air and water-oil interfaces

    , Article Soft Matter ; Volume 8, Issue 22 , 2012 , Pages 6057-6065 ; 1744683X (ISSN) Dan, A ; Kotsmar, C ; Ferri, J. K ; Javadi, A ; Karbaschi, M ; Krägel, J ; Wüstneck, R ; Miller, R ; Sharif University of Technology
    2012
    Abstract
    Mixed protein-surfactant adsorption layers can be built up in two different ways. The classical way is when all components adsorb simultaneously from a mixed solution. Alternatively, the components adsorb one after another, i.e. in a sequential way. In the present work, the formation of such surface layers has been studied with the random coil protein β-casein in the presence of added anionic surfactant SDS and compared for two different interfaces: the water-air (W-A) and water-hexane (W-H) interfaces. The used experimental technique is a drop profile analysis tensiometer PAT-1 specially equipped with a coaxial double capillary for drop volume exchange during the experiments. The results... 

    Evaluation of ceramic/ceramic joint interface prepared via brazing

    , Article Materials Forum, 18 October 2011 through 20 October 2011 ; Volume 35 , October , 2011 , Pages 20-30 ; 08832900 (ISSN) ; 9781876855369 (ISBN) Ghazi Daryani, A ; Nemati, A ; Sharif University of Technology
    Abstract
    Recent investigations show that ceramic/ceramic joints have high potential for applications in industry. Cost and difficulty in manufacturing complex components, either in one step or by joining of ceramic-metal and ceramic-ceramic, have inhibited more widespread use. It is important to know how to join components without problems and to understand the role of the interface as the main factor controlling the properties in these joints. The purpose of this paper was to investigate the joining of two ceramics with metal fillers (SiC to SiC and Al2O3 to Al2O3) and to investigate the interface of SiC/SiC and Al2O3/Al 2O3 with the same metal interlayer (Ag-Cu-Ti) and the effects on the... 

    Two phase modal analysis of nonlinear sloshing in a rectangular container

    , Article Ocean Engineering ; Volume 38, Issue 11-12 , August , 2011 , Pages 1277-1282 ; 00298018 (ISSN) Ansari, M. R ; Firouz Abadi, R. D ; Ghasemi, M ; Sharif University of Technology
    2011
    Abstract
    Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes... 

    Investigation on the bond strength of Al-1100/St-12 roll bonded sheets, optimization and characterization

    , Article Materials and Design ; Volume 32, Issue 6 , 2011 , Pages 3143-3149 ; 02641275 (ISSN) Movahedi, M ; Kokabi, A. H ; Seyed Reihani, S. M ; Sharif University of Technology
    Abstract
    Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in... 

    Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers

    , Article Materials Letters ; Volume 65, Issue 3 , February , 2011 , Pages 523-526 ; 0167577X (ISSN) Dourandish, M ; Simchi, A ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
    Abstract
    Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the... 

    Surface and interface effects on torsion of eccentrically two-phase fcc circular nanorods: Determination of the surface/interface elastic properties via an atomistic approach

    , Article Journal of Applied Mechanics, Transactions ASME ; Volume 78, Issue 1 , October , 2011 , Pages 0110111-01101111 ; 00218936 (ISSN) Pahlevani, L ; Shodja, H. M ; Sharif University of Technology
    2011
    Abstract
    The effect of surface and interface elasticity in the analysis of the Saint-Venant torsion problem of an eccentrically two-phase fcc circular nanorod is considered; description of the behavior of such a small structure via usual classical theories cease to hold. In this work, the problem is formulated in the context of the surface/interface elasticity. For a rigorous solution of the proposed problem, conformal mapping with a Laurent series expansion are employed together. The numerical results well illustrate that the torsional rigidity and stress distribution corresponding to such nanosized structural elements are significantly affected by the size. In order to employ surface and interface... 

    Thermal decomposition of nanostructured Aluminum Titanate in an active Al matrix: A novel approach to fabrication of in situ Al/Al2O3-Al3Ti composites

    , Article Materials and Design ; Volume 88 , 2015 , Pages 932-941 ; 02641275 (ISSN) Azarniya, A ; Hosseini, H. R. M ; Jafari, M ; Bagheri, N ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    The thermal decomposition of Aluminum Titanate in exposure to pure Aluminum was examined both in powder and in bulk form. Optical microscopy, FE-SEM, XRD, DSC and TGA examinations were conducted to take the possible chemical reactions between Aluminum Titanate and Al into consideration. It was found that as Aluminum Titanate particles are exposed to Al matrix, the thermal stability of Aluminum Titanate is degraded and its decomposition temperature is reduced from 850°C to 550°C. Also, the chemical reactions between Aluminum Titanate and Al start along the interfaces, and the reaction products, i.e. Al3Ti, Al2O3, TiO2 and O2 gas are left there. A mechanism was suggested to describe the... 

    Simulation of heat transfer in nanoscale flow using molecular dynamics

    , Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; Issue PARTS A AND B , 2010 , Pages 1563-1568 ; 9780791854501 (ISBN) Darbandi, M ; Abbasi, H. R ; Sabouri, M ; Khaledi Alidusti, R ; Sharif University of Technology
    2010
    Abstract
    We investigate heat transfer between parallel plates separated by liquid argon using two-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. In molecular dynamics simulation of nanoscale flows through nanochannels, it is customary to fix the wall molecules. However, this approach cannot suitably model the heat transfer between the fluid molecules and wall molecules. Alternatively, we use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the... 

    Fuzzy clustering of vertical two phase flow regimes based on image processing technique

    , Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM, 1 August 2010 through 5 August 2010, Montreal, QC ; Volume 2 , 2010 , Pages 303-313 ; 08888116 (ISSN) ; 9780791849491 (ISBN) Ghanbarzadeh, S ; Hanafizadeh, P ; Hassan, M ; Bozorgmehry, R. B ; Sharif University of Technology
    2010
    Abstract
    In order to safe design and optimize performance of industrial systems which work under two phase flow conditions, it's often needed to categorize flow into different regimes. In present work the experiments of two phase flow were done in a large scale test facility with length of 6m and 5cm diameter. Four main flow regimes were observed in vertical air-water two phase flows at moderate superficial velocities of gas and water: Bubbly, Slug, Churn and Annular. Some image processing techniques were used to extract information from each picture. This information include number of bubbles or objects, area, perimeter, height and width of objects (second phase).Also a texture feature extraction... 

    Torsion of an eccentrically two-phase circular nanobar

    , Article 2010 IEEE 5th International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2010, 20 January 2010 through 23 January 2010 ; January , 2010 , Pages 70-73 ; 9781424465439 (ISBN) Pahlevani, L ; Shodja, H. M ; Sharif University of Technology
    2010
    Abstract
    The effect of surface and interface elasticity in analysis of the Saint-Venant torsion problem of an eccentrically two-phase circular nanobar is considered. The problem is formulated in the context of Gurtin's surface elasticity. For a rigorous solution of the proposed problem, conformal mapping together with a Laurent series expansion are employed. At the nanoscales the usual classical theories cease to hold and the corresponding results deteriorate. The numerical results well illustrate that the torsional rigidity of the mentioned nanosized structural elements are significantly affected by the size. Some applications of the given results can be contemplated in the design of micro/nano... 

    On the formation of intermetallics during the furnace brazing of pure titanium to 304 stainless steel using Ag (30-50%)-Cu filler metals

    , Article Materials and Manufacturing Processes ; Volume 25, Issue 11 , 2010 , Pages 1333-1340 ; 10426914 (ISSN) Shafiei, A ; Abachi, P ; Dehghani, K ; Pourazarang, K ; Sharif University of Technology
    2010
    Abstract
    In the present work, the effect of brazing pa rameters on the properties of the brazed joint of pure titanium and 304 stainless steel (304SS) was investigated. Three different Ag-Cu filler metals were used, while the temperature and time of brazing were in the range of 800-950°C and 5-45 minutes, respectively. The microstructural observations show that, depending on the brazing conditions, different intermetallic phases such as CuTi2, CuTi, Cu3Ti4, and FeTi were formed at the phases interface. Based on the microstructural observations, a model was developed to characterize the formation of phases at the interfaces and brazed joint. The results show that, while some phases may form during the... 

    The effects of annealing phenomena on the energy absorption of roll-bonded Al-steel sheets during wedge tearing

    , Article Materials Science and Engineering A ; Volume 527, Issue 27-28 , 2010 , Pages 7329-7333 ; 09215093 (ISSN) Beygi, R ; Kazeminezhad, M ; Sharif University of Technology
    Abstract
    The purpose of this paper is to investigate the effects of annealing phenomena on the energy absorption of Al-steel bilayer sheets, bonded by cold rolling, through wedge tearing. Tearing by wedge is a dissipating energy system that includes three components: cutting, friction and plastic deformation due to bending. In order to find the bonding and annealing effects on energy absorption, the non-bonded bilayer sheets are prepared in the same condition of bonded ones. The results show that energy absorption of bonded sheets is larger than that of non-bonded ones. This is due to different plastic bending moment of bonded and non-bonded bilayer sheets. Whenever the bond is improved by heat... 

    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
    2010
    Abstract
    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... 

    Investigation of the interphase effects on the mechanical behavior of carbon nanotube polymer composites by multiscale modeling

    , Article Journal of Applied Polymer Science ; Volume 117, Issue 1 , March , 2010 , Pages 361-367 ; 00218995 (ISSN) Montazeri, A ; Naghdabadi, R ; Sharif University of Technology
    2010
    Abstract
    In this article, a multiscale modeling procedure is implemented to study the effect of interphase on the Young's modulus of CNT/polymer composites. For this purpose, a three-phase RVE is introduced which consists of three components, i.e., a carbon nanotube, an interphase layer, and an outer polymer matrix. The nanotube is modeled at the atomistic scale using molecular structural mechanics. Moreover, three-dimensional elements are employed to model the interphase layer and polymer matrix. The nanotube and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential at the interface. Using this Molecular Structural Mechanics/Finite Element... 

    Rheological and mechanical characteristics of low density polyethylene/ethylene-vinyl acetate/organoclay nanocomposites

    , Article Polymer Engineering and Science ; Volume 50, Issue 7 , March , 2010 , Pages 1315-1325 ; 00323888 (ISSN) Behradfar, A ; Shojaei, A ; Sheikh, N ; Sharif University of Technology
    2010
    Abstract
    Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LDPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA... 

    Analysis of structure-properties relationship in nitrile-butadiene rubber/phenolic resin/organoclay ternary nanocomposites using simple model system

    , Article Polymers for Advanced Technologies ; Volume 21, Issue 5 , April , 2010 , Pages 356-364 ; 10427147 (ISSN) Shojaei, A ; Faghihi, M ; Sharif University of Technology
    2010
    Abstract
    The present study deals with the structure-property relationship of organoclay (OC) filled nanocomposites based on rubber blend comprising of nitrile-butadiene rubber (NBR) and phenolic resin (PH). To obtain a better insight into the characteristics of the NBR/PH/OC hybrid system, a simple model system consisting of NBR/OC nanocomposites is also taken into consideration. A series of NBR/OC and NBR/PH/OC nanocomposites containing a wide range of OC concentrations (2.5-30 phr) are prepared by using traditional open two-roll mill. Structural analysis performed by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) exhibits mixed exfoliated and...