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    Synthesis of Magnesium Aluminate Spinel Nanoparticles Using Chemical Method and Investigation of the Effect of Zirconia on Spinel Composites Properties

    , M.Sc. Thesis Sharif University of Technology Maddahi, Vahid (Author) ; Nemati, Ali (Supervisor)
    Abstract
    In this research, a powder containing magnesium-aluminate spinel particles is prepared based on co-precipitation method and 5% , 10%, 15% and 20% zirconia-contained composites are produced as second phase from the synthesized powder. The raw materials used in the synthesis comprise hexa-hydrated magnesium nitrate, nona-hydrated aluminum nitrate, ammonium bicarbonate, 28% ammonium solution and distilled water. The properties of the powder is then investigated using STA, XRD and SEM tests. Also, XRD and SEM analyses as well as triple point flexural strength and Vickers hardness tests are carried out in order to investigate the effect of adding zirconia to the powders. The variations of the... 

    Flexural-torsional behavior of thin-walled composite beams with closed cross-section

    , Article Thin-Walled Structures ; Volume 45, Issue 7-8 , 2007 , Pages 699-705 ; 02638231 (ISSN) Shadmehri, F ; Haddadpour, H ; Kouchakzadeh, M. A ; Sharif University of Technology
    2007
    Abstract
    This paper investigates the static and dynamic characteristics of composite thin-walled beams that are constructed from a single-cell box. The structural model considered herein incorporates a number of nonclassical effects, such as material anisotropy, transverse shear, warping inhibition, nonuniform torsional model and rotary inertia. The governing equations were derived using extended Hamilton's principle and solved using extended Galerkin's method. The effects of fiber orientation on static deflection and natural frequencies are considered and a number of important conclusions are outlined. © 2007 Elsevier Ltd. All rights reserved  

    Seismic shear strengthening of R/C beams and columns with expanded steel meshes

    , Article Structural Engineering and Mechanics ; Volume 21, Issue 3 , 2005 , Pages 333-350 ; 12254568 (ISSN) Morshedt, R ; Kazemi, M. T ; Sharif University of Technology
    Techno-Press  2005
    Abstract
    This paper presents results of an experimental study to evaluate a new retrofit technique for strengthening shear deficient short concrete beams and columns. In this technique a mortar jacket reinforced with expanded steel meshes is used for retrofitting. Twelve short reinforced concrete specimens, including eight retrofitted ones, were tested. Six specimens were tested under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross section, Ag, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching... 

    Experimental study of RC jacketed and CFRP strengthened RC beams

    , Article Construction and Building Materials ; Volume 95 , October , 2015 , Pages 476-485 ; 09500618 (ISSN) Tahsiri, H ; Sedehi, O ; Khaloo, A ; Raisi, E. M ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    This paper presents the results of an experimental study on retrofitting RC beams using FRP strengthening and RC jacketing. Three-point loadings are applied to twelve strengthened beams and three reference specimens to put the two techniques into perspective. Formation of first cracks, FRP debonding, and onset of concrete crushing are compared and discussed. Load-deflection behavior, failure modes, and crack propagation patterns are studied extensively. The experiments demonstrate that the RC jacketed beams exhibit a flexural failure identical to the reference beams. However, the FRP strengthened beams fail in a relatively small deflection due to the premature FRP debonding. Furthermore, the... 

    Flexural behaviour of small steel fibre reinforced concrete slabs

    , Article Cement and Concrete Composites ; Volume 27, Issue 1 , 2005 , Pages 141-149 ; 09589465 (ISSN) Khaloo, A. R ; Afshari, M ; Sharif University of Technology
    2005
    Abstract
    Influence of length and volumetric percentage of steel fibres on energy absorption of concrete slabs with various concrete strengths is investigated by testing 28 small steel fibre reinforced concrete (SFRC) slabs under flexure. Variables included; fibre length, volumetric percentage of fibres and concrete strength. Test results indicate that generally longer fibres and higher fibre content provide higher energy absorption. The results are compared with a theoretical prediction based on random distribution of fibres. The theoretical method resulted in higher energy absorption than that obtained in experiment. A design method according to allowable deflection is proposed for SFRC slabs within... 

    Seismic shear strengthening of R/C columns with ferrocement jacket

    , Article Cement and Concrete Composites ; Volume 27, Issue 7-8 , 2005 , Pages 834-842 ; 09589465 (ISSN) Kazemi, M. T ; Morshed, R ; Sharif University of Technology
    2005
    Abstract
    This paper presents results of an experimental study to evaluate a retrofit technique for strengthening shear deficient short concrete columns. In this technique a ferrocement jacket reinforced with expanded steel meshes is used for retrofitting. Six short concrete columns, including four strengthened specimens, were tested. Specimens were under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross, A g, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching their nominal calculated flexural... 

    , M.Sc. Thesis Sharif University of Technology Kashani, Massoud (Author) ; Moghaddam, Hassan (Supervisor)
    Abstract
    The paper presents the results nonlinear analysis of steel base plates subjected to different combinations of axial and bending forces. The bending forces range from small moments representing small eccentricities to large moments from seismic actions. The results of analyses proved to be in good agreement with experiments. The parameters investigated in this study are as follows: distribution of strain and stresses in the concrete foundation and the steel plate, the strains and stresses in the tensile anchorage bolts, the location of neutral curve under the base plate, the centre of compressional reaction forces in concrete, the flextural rigidity of the base plate connection, and the axial... 

    Investigation on Nonlinear Behavior of base Plates with Triangular Hardener under Axial Load and Bending Moment

    , M.Sc. Thesis Sharif University of Technology Sheibani, Mehran (Author) ; Moghaddam, Hassan (Supervisor)
    Abstract
    The paper presents the results of nonlinear analysis of steel base plates subjected to different combinations of axial and bending forces. The bending forces range from small moments representing small eccentricities to large moments from seismic actions. The results of nonlinear analysis are done on three samples of the column base plate with large moment, small moment and compression axial force are compared to the results of the code. The parameters investigated in this study are as follows: distribution of strain and stresses in the concrete foundation and the steel plate, the strains and stresses in the tensile anchorage bolts, the location of neutral curve under the base plate, the... 

    The Investigation of Additive Elements Ti, Cr on Structure and Some Mechanical Properties of Micro and Nano Composites of Iron Aluminide/Alumina

    , M.Sc. Thesis Sharif University of Technology Khazraiyan Vafadar, Ali (Author) ; Abachi, Parvin (Supervisor) ; Salahi, Esmaeil (Supervisor)
    Abstract
    In this experiment, first the Fe and Al powders with atomic ratio of 25 and 75 were mixed by mechanical alloying process. After obtaining the optimum conditions of milling, nano structural Fe3Al powder was synthesized by 40 hours alloying with a Ball to Powder Ratio (BPR) of 20:1. The synthesized powder was then milled with different weight ratios of titanium and Cr for 30 hours. Morphological changes, size of powder particles, lattice strain, grain size and phase transitions were studied for different powders in different time spans during milling process by means of scanning electron microscopy, X-ray diffraction and grain size analyzer. The smallest grain size gained for milled powder... 

    Effect of Process Parameters on Microstructure and Mechanical Properties of Duplex Stainless Steel Produced by Wire-Arc Additive Manufacturing

    , M.Sc. Thesis Sharif University of Technology Torabi, Farnaz (Author) ; Ashouri, Hossein (Supervisor) ; Movahedi, Mojtaba (Supervisor)
    Abstract
    Wire-arc additive manufacturing is one of the types of additive manufacturing methods that creates the desired part through layer-by-layer deposition. Heat input and interlayer temperature have an important role in this process. Duplex stainless steels have a wide range of applications due to their high corrosion resistance in chloride environments and higher strength than austenitic stainless steels. In this study, the effect of heat input (0.3 kJ/mm and 0.8 kJ/mm) and interlayer temperature (250 ºC and 40 ºC) was investigated on the macrostructure, microstructure and mechanical properties of 2209 duplex stainless steel walls that produced by gas metal arc welding based wire-arc additive... 

    Mechanical performance of self-compacting concrete reinforced with steel fibers

    , Article Construction and Building Materials ; Volume 51 , 31 January , 2014 , Pages 179-186 ; ISSN: 09500618 Khaloo, A ; Raisi, E. M ; Hosseini, P ; Tahsiri, H ; Sharif University of Technology
    Abstract
    Self-compacting concrete (SCC) is a highly-workable concrete that without any vibration or impact and under its own weight fills the formwork, and it also passes easily through small spaces between rebars. In this paper, the effect of steel fibers on rheological properties, compressive strength, splitting tensile strength, flexural strength, and flexural toughness of SCC specimens, using four different steel fiber volume fractions (0.5%, 1%, 1.5%, and 2%), were investigated. Two mix designs with strengths of 40 MPa (medium strength) and 60 MPa (high strength) were considered. Rheological properties were determined through slump flow time and diameter, L-box, and V-funnel flow time tests.... 

    Investigation on cristobalite crystallization in silica-based ceramic cores for investment casting

    , Article Journal of the European Ceramic Society ; Volume 33, Issue 15-16 , 2013 , Pages 3397-3402 ; 09552219 (ISSN) Kazemi, A ; Faghihi Sani, M. A ; Alizadeh, H. R ; Sharif University of Technology
    2013
    Abstract
    In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process condition, the sintered samples at 1220 °C were also heated up to 1430 °C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43. wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was... 

    Effect of Zirconia Content and Powder Processing on Mechanical Properties of Gelcasted ZTA Composite

    , Article Transactions of the Indian Ceramic Society ; Volume 72, Issue 3 , May , 2013 , Pages 175-181 ; 0371750X (ISSN) Khoshkalam, M ; Faghihi Sani, M. A ; Nojoomi, A ; Sharif University of Technology
    2013
    Abstract
    Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods... 

    The Effect of Temperature and Rotational Speed on Structure and Mechanical Properties of Cast Cu Base Alloy (Cu-Al-Si-Fe) Welded by Semisolid Stir Joining Method

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 46, Issue 12 , 2015 , Pages 5782-5788 ; 10735623 (ISSN) Ferasat, K ; Aashuri, H ; Kokabi, A. H ; Shafizadeh, M ; Nikzad, S ; Sharif University of Technology
    Abstract
    Semisolid stir joining has been under deliberation as a possible method for joining of copper alloys. In this study, the effect of temperature and rotational speed of stirrer on macrostructure evaluation and mechanical properties of samples were investigated. Optical microscopy and X-ray diffraction were performed for macro and microstructural analysis. A uniform micro-hardness profile was attained by semisolid stir joining method. The ultimate shear strength and bending strength of welded samples were improved in comparison with the cast sample. There is also lower area porosity in welded samples than the cast metal. The mechanical properties were improved by increasing temperature and... 

    The influence of silica nanoparticles addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites

    , Article Ceramics International ; Volume 43, Issue 18 , 2017 , Pages 16780-16786 ; 02728842 (ISSN) Gheisari Dehsheikh, H ; Ghasemi Kahrizsangi, S ; Sharif University of Technology
    Abstract
    The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO2) addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8 mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5 wt% nano SiO2 as additives. Specimens were heated up to 1650 °C for the 3 h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and... 

    Anisotropic elastic-plastic behavior of architected pyramidal lattice materials

    , Article Acta Materialia ; Volume 183 , 2020 , Pages 118-136 Eynbeygui, M ; Arghavani, J ; Akbarzadeh, A. H ; Naghdabadi, R ; Sharif University of Technology
    Acta Materialia Inc  2020
    Abstract
    The initial and subsequent yield surfaces for architected pyramidal lattice materials are investigated analytically. Considering lattice struts as elastic-perfectly plastic thin beams subjected to both axial force and bending moment, a set of nonlinear elastic-plastic constitutive relations for a strut is proposed. Moreover, we phenomenologically present anisotropic pressure-dependent yield functions for pyramidal lattices. Comparison of planar yield surfaces of pyramidal lattices predicted by analytical approach to the ones obtained from phenomenological models shows a good agreement for the type of external loads and range of strains investigated in this study. Investigating the normality... 

    Mixed shear-flexural (VM) hinge element and its applications

    , Article Scientia Iranica ; Volume 14, Issue 3 , 2007 , Pages 193-204 ; 10263098 (ISSN) Kazemi, M. T ; Erfani, S ; Sharif University of Technology
    Sharif University of Technology  2007
    Abstract
    In the present paper, a mixed, shear-flexural (VM) hinge element, with zero or nonzero length, for using in frames, has been introduced, where shear-flexural interaction has been considered. The element has the capability of modeling flexural yielding, shear yielding and their interaction in frames, subjected to all kinds of monotonic or cyclic loadings. The inelastic shear and flexural deformations and tangential stiffnesses are considered by using the multi-surfaces approach with dissimilar yield surfaces and by a stiffness matrix with nonzero off-diagonal components. A new kinematics hardening rule and, also, a new non-associated flow rule are introduced. The mixed hinge element can be... 

    Mechanical characteristics of cement paste in the presence of carbon nanotubes and silica oxide nanoparticles: An experimental study

    , Article Materials ; Volume 14, Issue 6 , 2021 ; 19961944 (ISSN) Karakouzian, M ; Farhangi, V ; Farani, M. R ; Joshaghani, A ; Zadehmohamad, M ; Ahmadzadeh, M ; Sharif University of Technology
    MDPI AG  2021
    Abstract
    Considering the remarkable characteristics of nanomaterials, previous research studies investigated the effects of incorporating different types of these materials on improving the concrete properties. However, further studies are required to evaluate the complementary hybridization and synergistic influence of nanomaterials. In this research, the combined effect of adding nano silica particles (NS) and multi-walled carbon nanotubes (MWCNT) on enhancing both the compressive and flexural strengths of the cement paste was investigated. Moreover, the morphology of the interface between cement paste and aggregates was studied by scanning electron microscopy (SEM). The mixtures were prepared... 

    An analytical review on Spark Plasma Sintering of metals and alloys: from processing window, phase transformation, and property perspective

    , Article Critical Reviews in Solid State and Materials Sciences ; 2022 ; 10408436 (ISSN) Abedi, M ; Sovizi, S ; Azarniya, A ; Giuntini, D ; Seraji, M. E ; Hosseini, H. R. M ; Amutha, C ; Ramakrishna, S ; Mukasyan, A ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    ABSTRACTs: The need for fully dense material with well-engineered microstructures has led to the promising emergence of innovative sintering technologies among which the Spark Plasma Sintering (SPS) is one of the most favorite. Unlike the conventional sintering processes, SPS takes advantage of a current flow passing through the sintering die and metallic powders by which fast densification with minimal grain growth and enhanced physicomechanical properties can be obtained. Albeit there is a growing interest in the exploitation of SPS in producing sufficiently consolidated metallic parts, no analytical review has been released over the effects of SPS parameters on the densification behavior,... 

    Production of waste bio-fiber cement-based composites reinforced with nano-SiO 2 particles as a substitute for asbestos cement composites

    , Article Construction and Building Materials ; Volume 31 , 2012 , Pages 105-111 ; 09500618 (ISSN) Hosseinpourpia, R ; Varshoee, A ; Soltani, M ; Hosseini, P ; Ziaei Tabari, H ; Sharif University of Technology
    2012
    Abstract
    The environmental impact of asbestos fibers on human health and their consequent safety-related problems indicate that there is a significant need to replace this material in all asbestos-containing products. Many different types of fibers have been introduced to replace asbestos fibers. In this study, the performance of silica nano-particles combined with waste paper pulp fibers (sulfite fibers) has been investigated. Different mechanical (compressive and flexural strengths and bending performance), durability (water absorption), physical (bulk density and flowability), and microstructural (scanning electron microscopy) tests were conducted to examine the properties of manufactured green...