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    Evaluation of Mechanical and Structural Properties of Titanium Bone Scaffolds

    , M.Sc. Thesis Sharif University of Technology Naddaf Dezfuli, Sina (Author) ; Sadrnezhad, Khatiboleslam (Supervisor) ; Shokrgozaar, Mohammad Ali (Co-Supervisor)
    Interconnected–pore titanium scaffolds were fabricated by sintering of compressed mixture of TiH1.924 and urea or NaCl. Urea was removed by evaporation during sintering and NaCl was removed with water. TiH1.924 was used to enhance gas evolution for perpetuation of foam formation. Morphological studies of the spacer-removed scaffolds showed that the spacer shapes were replicated to the pores. Minimization of stress concentration at walls of the pores was, hence, helped by utilization of the spacers with spherical particles. The scaffolds having relative densities of 0.34 to 0.65 consisted pores of 200 to 600 μm diameter, compression strengths of 51 to 260 MPa, Young’s modulus of 6.3 to 22.66... 

    Effect of nanoclays on the mechanical properties and durability of novolac phenolic resin/woven glass fiber composite at various chemical environments

    , Article Composites Part A: Applied Science and Manufacturing ; Vol. 63 , 2014 , pp. 149-158 ; ISSN: 1359835X Eesaee, M ; Shojaei, A ; Sharif University of Technology
    Both natural montmorilonite (CN) and organically modified montmorilonite (CB) improved significantly the mechanical performance of novolac phenolic resin (PF)/woven glass-fiber (GF) composites due to their nanodispersion and good interfacial interaction with the matrix. It was revealed that the incorporation of 2.5 wt% of the clays enhances the elastic modulus up to 38% for CN and 43% for CB. Aging of PF/GF composites at various aqueous solutions, i.e. water, brine and acidic environments, increased stiffness of the composite (∼100-250% increase in elastic modulus) due to possible secondary crosslinking caused by water molecules and hydroxyl groups of PF resin. However, aging led to the... 

    Effect of Carbon Content on Mechanical Properties of TLP Bonded Ferrite- Martensite Dual Phase Steels

    , M.Sc. Thesis Sharif University of Technology Elyasi Boroojeni, Forood (Author) ; Ekrami, Ali Akbar (Supervisor)
    During the last few years researchers have drawn much attention to HSLA steels because of the application of these steels in many industries. Ferrite-martensite dual phase(DP) steels are one of the most common HSLA steels which are currently used. Combination of these two phases provides good strength along with good ductility. Joining and welding of these steels has always been an important challenge. The aim of this study is to examine applicability of TLP method for joining and dual phase processing of this steels at the same time. Microstructural and mechanical examination of the bonded specimens showed that isothermal solidification occurred during holding for 50 min at the... 

    The Effect of Pressure on Microstructure and Mechanical Properties of TLP Bonded Dual Phase Steels

    , M.Sc. Thesis Sharif University of Technology Fathi, Mohammad (Author) ; Ekrami, Ali Akbar (Supervisor)
    Dual Phase ferritic-martensitic steels are kind of high strength low alloy steels (HASLA) which are widely used in industry because of their strength and formability. Since welding of dual phase steels in conventional welding methods causes structural change and Subsequently alters mechanical properties of both weld zone and heat affected zone(HAZ), additional operations which are not commercially viable is needed to achieve a dual phase structure in structurally changed regions. In this study, transient liquid phase (TLP) bonding method is used during dual phasing process in order to preserve dual phase ferritic-martensitic structure and avoid extra heat treatment. Applied pressure during... 

    Prediction of Temperature and Strain Distribution in the Warm Rolling of Austenite Stainless Steel

    , M.Sc. Thesis Sharif University of Technology Nemati, Elham (Author) ; Serajzadeh, Siamak (Supervisor)
    In this research, the hot and warm rolling of stainless steel 304 was studied. First the rolling process was simulated using Finite Element Method software ABAQUS and the distribution of temperature and strain in the process under discontinuous conditions were predicted. Next, hot and warm rolling of stainless steel 304 under different conditions was carried out. Specimens were cut and subject to mechanical testing, metallography and electron microscopic studies. Data obtained from these experiments and the predicted trends from ABAQUS were compared, therefore studying the effect of different parameters on the microstructure and mechanical properties of the rolled specimen. Results indicate... 

    Test data compression strategy while using hybrid-BIST methodology

    , Article Proceedings of IEEE East-West Design and Test Symposium, EWDTS 2013, Rostov-on-Don ; Sept , 2013 ; 9781479920969 (ISBN) Karimi, E ; Tabandeh, M ; Haghbayan, M. H ; Sharif University of Technology
    In this paper a strategy is proposed for compressing the test data while using concurrent hybrid-BIST methodologyfor testing SoCs. In the proposed method, in addition tousing BIST strategy for testing cores with deterministic sequential test patterns in an SoC( Without using scan chains), (ATE) is used for testing cores with deterministic test patterns through Test Access Mechanism (TAM) or functional bus. As will be shown in experimental results, this process compresses hybrid-BIST overall test patterns considerably that affects the overall Test Application Time (TAT) in comparison with pure deterministic, pure pseudo random, and combination of deterministic and pseudo random test patterns  

    Effect of molybdenum on grain boundary segregation in Incoloy 901 superalloy

    , Article Materials and Design ; Volume 46 , 2013 , Pages 573-578 ; 02641275 (ISSN) Tavakkoli, M. M ; Abbasi, S. M ; Sharif University of Technology
    In this paper, the effect of molybdenum on the grain boundary segregation of other elements was studied in Incoloy 901 superalloy. Initially, five alloys were prepared with different percentages of Mo by using a vacuum induction furnace. Then, these alloys were remelted by Electro-slag remelting (ESR) process and after homogenizing at 1160 °C for 2. h followed by air cooling, were rolled. The effect of Mo on segregation of elements was evaluated with Scanning Electron Microscopy, Linear Analysis, and the mechanical tests. The results showed that the grain boundary segregations of elements in Incoloy 901 superalloy were decreased by increasing of molybdenum content up to 6.7% and the... 

    Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

    , Article Materials and Design ; Volume 50 , 2013 , Pages 85-91 ; 02641275 (ISSN) Soltani, N ; Pech Canul, M. I ; Bahrami, A ; Sharif University of Technology
    Elsevier Ltd  2013
    A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al2O3 particles on the microstructure and properties of Al/(10Ce-TZP/Al2O3) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30μm were ball-milled with 10Ce-TZP/Al2O3 nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600MPa for 60min while heating at 400-450°C. The specimens were then characterized by scanning and... 

    Microstructure-mechanical Properties Relationship of Transient Liquid Phase Bonded 304 Stainless Steel With a Co-based Interlayer

    , M.Sc. Thesis Sharif University of Technology Sadeghian, Mohammad (Author) ; Ekrami, Ali Akbar (Supervisor)
    Stainless steels have many applications in different industries like chemistry, medicine and food production. So for using these alloys it is necessary to join them with appropriate method. In this research, microstructure-mechanical properties relationship of 304LC austenitic stainless steel transient liquid phase bonded using a Co-based interlayer was investigated. For this purpose, bonding was conducted at 1180 ℃ for different holding times. Microstructure of the joints was evaluated by optical microscopy (OM) and Scanning Electron Microscopy (SEM). The results showed that isothermal solidification (IS) was completed within 1800s and no intermetallic compound was formed in the joint area... 

    TLP Bonding of Ferrite - Martensite Dual Phase Steel and Comparison with Fusion Welding Method

    , M.Sc. Thesis Sharif University of Technology Dehghanzadeh, Masoud (Author) ; Ekrami, Ali Akbar (Supervisor)
    In this study, low carbon plain steels joined with TLP bonding method using Fe-44Ni-7B-4Mo interlayer, The bonding parameters (holding time, temperature) have been changed to find optimum conditions of TLP bonding. Microstructure and properties of joints have also been investigated. Dual phase processing of the used steel has been carried out during joints homogenization. Microstructural studies with scanning electron microscope and optical microscope showed that isothermal solidification completed at holding for 50 minutes at the bonding temperature of 1180℃. These parameters are taken as optimum conditions of TLP bonding. Microstructure of the isothermally solidified zone (joint region)... 

    Characterization of reinforcing effect of alumina nanoparticles on the novolac phenolic resin

    , Article Polymer Composites ; Vol. 35, Issue 7 , July , 2014 , pp. 1285-1293 ; ISSN: 02728397 Etemadi, H ; Shojaei, A ; Sharif University of Technology
    Very fine alumina nanoparticles were loaded in novolac type phenolic resin (PF) using solution mixing method. The concentration of nanoalumina in PF was varied between 2.5 to 20 wt%. All the compounds were compression molded and then subjected to scanning electron microscopy (SEM), tensile, flexural, and dynamic mechanical analysis (DMA) tests. SEM analysis showed that the nanoalumina were dispersed uniformly at low concentrations, however, at high concentrations, dispersion was suppressed leading to agglomerates in the composites. Mechanical testing revealed that the nanoalumina had a great influence on the strength and stiffness of PF resin particularly at concentrations below 5 wt%.... 

    Analysis of strain rate sensitivity of ultrafine-grained AA1050 by stress relaxation test

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 45, Issue 12 , November 2014 , Pages 5442-5450 Mohebbi, M. S ; Akbarzadeh, A ; Kim, B. H ; Kim, S. K ; Sharif University of Technology
    Commercially pure aluminum sheets, AA 1050, are processed by accumulative roll bonding (ARB) up to eight cycles to achieve ultrafine-grained (UFG) aluminum as primary material for mechanical testing. Optical microscopy and electron backscattering diffraction analysis are used for microstructural analysis of the processed sheets. Strain rate sensitivity (m-value) of the specimens is measured over a wide range of strain rates by stress relaxation test under plane strain compression. It is shown that the flow stress activation volume is reduced by decrease of the grain size. This reduction which follows a linear relation for UFG specimens, is thought to enhance the required effective (or... 

    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
    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... 

    Effect of rolling speed on the occurrence of strain aging during and after warm rolling of a low-carbon steel

    , Article Journal of Materials Science ; Volume 45, Issue 13 , July , 2010 , Pages 3405-3412 ; 00222461 (ISSN) Koohbor, B ; Ohadi, D ; Serajzadeh, S ; Akhgar, J. M ; Sharif University of Technology
    In this study, effect of rolling speed on strain aging phenomena in warm rolling of a carbon steel has been investigated. For this purpose, by using a mathematical model and predicting temperature and strain rate fields, the possibility of occurrence of dynamic strain aging during the warm rolling was first evaluated. In the next stage, warm-rolled samples were aged up to 11 months at room temperature for studying the kinetics of static strain aging, while mechanical tests as well as microstructural evolutions have been performed to determine the effect of strain aging on material behavior. The results indicate that dynamic strain aging may not occur for the employed rolling program;... 

    The effect of gypsum cementation on the mechanical behavior of gravely sands

    , Article Geotechnical Testing Journal ; Volume 28, Issue 4 , 2005 , Pages 380-390 ; 01496115 (ISSN) Haeri, S. M ; Hamidi, A ; Tabatabaee, N ; Sharif University of Technology
    The behavior of a cemented gravely sand is studied using triaxial tests. Drained and undrained tests were performed on dry and saturated specimens, and stress-strain characteristics of the soil, along with volumetric and pore pressure changes, were identified. The gypsum plaster was used as the cement agent and was mixed with the soil in different percentages. The tests were done in the usual range of confining pressures, from 25 to 500 kPa. Test results show that dilation occurs even at the highest confining stress and the least cement content. The behavior of the cemented soil is found to be more brittle in drained condition than the undrained one. However, the brittleness of soil... 

    Improving the Failure Behavior of High Strength and High Hardenable Steels Resistance Spot Welds

    , M.Sc. Thesis Sharif University of Technology Aghajani, Hamid Reza (Author) ; Pouranvari, Majid (Supervisor)
    Selecting materials is a key stage for designing vehicles. Today, advanced high-strength steels and stainless steels are attractive by the automotive industry. In this study, the improvement of mechanical properties of the martensitic stainless steels (MSS420 with annealed condition) and advanced high strength martensitic steels (MS1400 with quenched condition), which have a different response to mechanical tests, were investigated. The welding of MSS420 steel was carried out in three phases. In the first phase, the MSS420 double pulse welding with variable second pulse times (0.2s-1.8s) with a constant secondary pulse current of 4 kA and in the second phase a double pulse welding with... 

    Ceria reinforced nanocomposite solder foils fabricated by accumulative roll bonding process

    , Article Journal of Materials Science: Materials in Electronics ; Volume 23, Issue 9 , September , 2012 , Pages 1698-1704 ; 09574522 (ISSN) Roshanghias, A ; Kokabi, A. H ; Miyashita, Y ; Mutoh, Y ; Rezayat, M ; Madaah Hosseini, H. R ; Sharif University of Technology
    Springer  2012
    As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this study, accumulative roll bonding process was used as an effective alternative method for manufacturing high-strength, finely dispersed, void-free and highly uniform Sn-Ag-Cu/CeO 2 nanocomposite solders. Microstructural investigation of nanocomposite solders revealed that homogenous distribution of CeO 2 nanoparticle has been achieved and the eutectic as-cast morphology of the solder changed to recrystallized fine grained structure. As a result of severe plastic deformation during rolling, brittle and... 

    Experimental and numerical investigation of pulse-shaped split Hopkinson pressure bar test

    , Article Materials Science and Engineering A ; Volume 539 , 2012 , Pages 285-293 ; 09215093 (ISSN) Naghdabadi, R ; Ashrafi, M. J ; Arghavani, J ; Sharif University of Technology
    Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-hardening materials. Also, for... 

    Investigation into characteristics of Portevin-Le Chatelier effect of an Al-Mg Alloy

    , Article Journal of Materials Engineering and Performance ; Volume 19, Issue 9 , 2010 , Pages 1264-1267 ; 10599495 (ISSN) Sheikh, H ; Sharif University of Technology
    In this study, the plastic instabilities associated with the Portevin-Le Chatelier (PLC) and their effects on the mechanical properties and the fracture surfaces have been investigated for AA 5083. Tensile tests were performed at various temperatures and strain rates in order to do so. Then, serrated and smooth yielding domains were determined in Ln ε̇-1/T diagram. The stress-strain curves related to the serrated domain show the values of flow stress decreases by increasing the strain rate at a constant temperature. In addition, the plot of critical strain versus imposed strain rate indicates an inverse manner at very low strain rates. It is confirmed that the type of PLC bands alters the... 

    Production of granulated-copper oxide nanoparticles for catalytic application

    , Article Journal of Materials Research ; Volume 25, Issue 10 , 2010 , Pages 2025-2034 ; 08842914 (ISSN) Hosseinpour, M ; Ahmadi, S. J ; Mousavand, T ; Outokesh, M ; Sharif University of Technology
    Ultra fine CuO nanoparticles In the range of 2 ± 0.2 nm were synthesized by the supercritical hiydrotliermal method in a batch reactor. Itwas demonstrated that elevating the pH of the Cu2+ precursor solution to around 6 (neutral condition) not only does not lead to excessive agglomeration of the particles, but also reduces particle size and in general promotes their nanoscale characteristics. Prepared nanoparticles were immobilized in the biopolymcric matrix of barium alginate and calcined at different temperatures resulting in micro spherical granules of high porosity and elevated mechanical strength. The fabricated samples were characterized using x-ray diffractometry (XRD), transmission...