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    Aging behavior and tensile properties of squeeze cast AL 6061/SIC metal matrix composites

    , Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 392-397 ; 10263098 (ISSN) Ehsani, R ; Seyed Reihani, S. M ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    In this work, the production and properties of Al 6061/SiC composites, made using a squeeze casting method, were investigated. SiC preforms were manufactured by mixing SiC powder, having a 16 and 22 pm particle size, with colloidal silica as a binder. 6061 Al melt was squeeze cast into the pores of the SiC preform to manufacture a DRA composite containing 30v/o reinforcement. The aging behavior, tensile properties and fracture mechanism of the cast material were studied. The results show that higher hardness, yield strength, tensile strength and Young's modulus can be obtained by the addition of SiC particles to 6061 Al alloy, whereas tensile elongation decreases. This is mainly caused by a... 

    Effects of hydrogen level and cooling rate on ultimate tensile strength of Al A319 alloy

    , Article Russian Journal of Non-Ferrous Metals ; Vol. 55, issue. 4 , July , 2014 , p. 365-370 ; 10678212 Bahmani, A ; Eisaabadi, G. B ; Davami, P ; Varahram, N ; Shabani, M. O ; Sharif University of Technology
    Abstract
    The present study investigated the effects of initial Hydrogen level and cooling rate on ultimate tensile strength of commercial Al-A319 alloys. Three hydrogen levels (0.01, 0.2, and 0.41 mL/100 grams of melt) and five cooling rate were studied. Total of 45 tensile test bars was prepared (three hydrogen levels × five cooling rate × three repeats). The UTS of the samples was determined though uniaxial tension tests. Furthermore, the microstructures of the samples were studied by standard metallographic technique and image analysis software. Finally the relationship between UTS and microstructurai features—SDAS and fraction of porosity (Fp%)—of the alloys was investigated.Results of tensile... 

    A study on the mechanical properties of graphene oxide/epoxy nanocomposites

    , Article Polymers and Polymer Composites ; Volume 29, Issue 9_suppl , 2021 , Pages S556-S564 ; 09673911 (ISSN) Eqra, R ; Moghim, M. H ; Eqra, N ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    The aims of this research are to elucidate the role of graphene oxide on the mechanical properties of epoxy and also to obtain an equation for the modeling of its behavior. Accordingly, graphene oxide/epoxy nanocomposite samples are fabricated using the solution casting method. Tensile, flexural, SEM and FTIR tests are conducted on epoxy and the nanocomposite samples afterwards. The obtained results show that the tensile strength of epoxy improves even at low contents of graphene oxide such that 0.3 wt.% of GO yields an improvement of approximately 11.5%. The flexural strength of epoxy is also enhanced by 5.8% with 0.5 wt.% GO. Then, it decreases due to the agglomeration with increasing the... 

    Impact and tensile behaviour of fractional melting processed ZA-27 alloy

    , Article Materials Science and Engineering A ; Volume 333, Issue 1-2 , 2002 , Pages 115-122 ; 09215093 (ISSN) Aashuri, H ; Razavimanesh, A ; Kolahi, A ; Mohiedin, M ; Sharif University of Technology
    2002
    Abstract
    This paper describes the influence of a fractional melting process on the reduction of interdendritic phases, which in turn have an impact on the tensile strength of ZA-27 alloys. The procedure consists of compressing a semi-solid specimen through a porous grinding disc, resulting on coarsening of the dendritic phase, reduction of the microporosity and homogenization of the alloy. © 2002 Elsevier Science B.V. All rights reserved  

    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.... 

    The effect of Ti on mechanical properties of extruded in-situ Al-15 pct Mg2Si composite

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 9 , September , 2013 , Pages 4366-4373 ; 10735623 (ISSN) Soltani, N ; Bahrami, A ; Pech Canul, M. I ; Sharif University of Technology
    2013
    Abstract
    This work was carried out to investigate the effect of different Ti concentrations as a modifying agent on the microstructure and tensile properties of an in-situ Al-15 pctMg2Si composite. Cast, modified, homogenized small ingots were extruded at 753 K (480°C) at the extrusion ratio of 18:1 and ram speed of 1 mm/s. Various techniques including metallography, tensile testing, scanning electron microscopy were used to characterize the mechanical behavior, microstructural observations, fracture mechanisms of this composite. The results showed that 0.5 pctTi addition and homogenizing treatment were highly effective in modifying Mg2Si particles. The results also exhibited that the addition of Ti... 

    Rutting and moisture resistance evaluation of polyethylene wax–modified asphalt mixtures

    , Article Petroleum Science and Technology ; Volume 34, Issue 17-18 , 2016 , Pages 1568-1573 ; 10916466 (ISSN) Nakhaei, M ; Darbandi Olia, A. D ; Akbari Nasrekani, A ; Asadi, P ; Sharif University of Technology
    Taylor and Francis Inc 
    Abstract
    One of the methods newly introduced in pavement technology to address environmental concerns and reduce total gas emission is warm mix asphalt (WMA) technology. In this study, polyethylene wax is used to produce WMA mixtures. Although this technology has several positive features, moisture and rutting resistance of WMA mixtures are always questionable. To evaluate moisture and rutting resistance of polyethylene-modified mixtures, indirect tensile strength and dynamic creep tests were used, respectively. Results indicated that polyethylene has positive effect at low compaction temperature on moisture resistance, and also has negative effect on rutting resistance  

    Mechanical properties of graphene oxide: A molecular dynamics study

    , Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 24, Issue 9 , 2016 , Pages 594-603 ; 1536383X (ISSN) Khoei, A. R ; Sarkari Khorrami, M ; Sharif University of Technology
    Taylor and Francis Inc 
    Abstract
    In this paper, the mechanical properties of graphene oxide are obtained using the molecular dynamics analysis, including the ultimate stress, Young modulus, shear modulus and elastic constants, and the results are compared with those of pristine graphene. It is observed that the increase of oxide agents (–O) and (–OH) leads to the increase of C–C bond length at each hexagonal lattice and as a result, alter the mechanical properties of the graphene sheet. It is shown that the elasticity modulus and ultimate tensile strength of graphene oxides (–O) and (–OH) decrease significantly causing the failure behavior of graphene sheet changes from the brittle to ductile. The results of shear loading... 

    Formability of friction stir-welded blanks with different thickness ratios

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 47, Issue 5 , 2016 , Pages 2177-2187 ; 10735623 (ISSN) Kolahgar, S ; Ghaffarpour, M ; Habibi, N ; Kokabi, A. H ; Akbarzadeh, A ; Sharif University of Technology
    Springer Boston 
    Abstract
    Welded sheets with different thicknesses are one of the interesting types of tailor-welded blanks (TWBs) that are widely used in metal-forming industries. In the present work, the formability behavior of different 1100-aluminum TWBs was studied. In this regard, the TWBs were made with different thickness ratios by using friction stir welding (FSW) at different welding rotational speeds (ω). The thickness ratios of 1.0, 1.3, and 1.7 were investigated where the thinner sheets had 1.5 mm thick for all conditions; i.e., the volume of welded material increased when the thickness ratio increased. Macrostructural observations, mechanical investigations, and sheet-forming limit tests were... 

    Mechanical and microstructural investigation of friction stir processed Al1100

    , Article Welding in the World ; Volume 53, Issue SPECIAL ISSUE , 2009 , Pages 253-258 ; 00432288 (ISSN) Nasiri, A. M ; Pouraliakbar, H ; Nikravesh, M ; Kokabi, A. H ; Sharif University of Technology
    Abstract
    Surfaces of cast 1100 aluminum were treated by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using frictional heat and stirring action. An improvement in the mechanical properties was accomplished due to the microstructural modification and reduction of porosities. The yield strengths of the MP-FSPed specimens were significantly increased to about 1.4 times versus that of the base metal. The elongation of MP-FSP sample is about 30% higher than that of the base metal. Also the ultimate tensile strength and hardness of MP-FSPed specimens are improved. Moreover the effect of tool rotation rate and tool travel speed on the mechanical... 

    A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites

    , Article International Journal of Minerals, Metallurgy and Materials ; Volume 27, Issue 8 , 2020 , Pages 1133-1146 Bagheri, B ; Abbasi, M ; Abdollahzadeh, A ; Kokabi, A. H ; Sharif University of Technology
    University of Science and Technology Beijing  2020
    Abstract
    Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results... 

    Effect of graphene and process parameters on mechanical performance and electrical resistance of aluminum to copper friction stir joint

    , Article Materials Research Express ; Volume 6, Issue 4 , 2019 ; 20531591 (ISSN) Montazerian, M. H ; Movahedi, M ; Jondi, M. R ; Sharif University of Technology
    Institute of Physics Publishing  2019
    Abstract
    Effects of graphene, tool rotational speed and pass number were studied on the reliability and electrical resistance of the aluminum to copper friction stir welds. Addition of graphene was an effective solution to overcome the increase in the electrical resistance of the aluminum/copper joints. Indeed, presence of graphene decreased the electrical resistance of the joints to the values comparable with that of the copper base metal. However, joint tensile strength was not affected significantly by graphene. Decrease in the tool rotational speed improved the dispersion of the graphene particles and tensile strength, while reduced the electrical resistance. Tensile strength of the joint reached... 

    Fatigue properties of machinable austempered ductile iron

    , Article 16th International Metallurgical and Materials Conference, METAL 2007, 22 May 2007 through 24 May 2007 ; 2007 Tadayon Saidi, M ; Baghersaee, N ; Varahram, N ; Hanumantha Rao, M ; Sharif University of Technology
    TANGER spol. s r.o  2007
    Abstract
    MADI is new engineering material with very desirable properties such as higher strength at the same hardness compared to regular ductile iron, significantly better fatigue performance than regular ductile iron or austempered ductile iron, better machinability than regular austempered ductile iron and similar to as cast ductile iron. In this study,fatigue properties of Machinable Austempering Ductile was investigated using rotary -bend fatigue testing device. Chemical composition of sample was selected on the base of previous work which results in good mechanical properties and low hardness after austempering process. The results of this study,indicates that for an austempered ductile iron... 

    A study of mechanical and microstructures properties of autoclaved aerated concrete containing nano-graphene

    , Article Journal of Building Engineering ; Volume 43 , 2021 ; 23527102 (ISSN) Seddighi, F ; Pachideh, G ; Salimbahrami, S. B ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    In recent years, the autoclaved aerated concrete (AAC) has been widely used in the building construction industry, especially for construction of infill walls. However, the AAC suffers from several drawbacks such as low compressive and tensile strength, high water absorption as well as insufficient resistance against impacts. To address such issues, this study evaluates the mechanical properties of the AAC blocks in which, the cement has been replaced with nano-graphene. For this purpose, various replacement ratios (0.2, 0.4, and 0.8) were selected and different tests such as compressive and tensile strength (cylindrical specimens with the size of 10 × 20 cm), impact resistance and water... 

    Tensile fracture behavior of heterogeneous materials based on fractal geometry

    , Article Theoretical and Applied Fracture Mechanics ; Volume 46, Issue 1 , 2006 , Pages 46-56 ; 01678442 (ISSN) Khezrzadeh, H ; Mofid, M ; Sharif University of Technology
    2006
    Abstract
    Many of heterogeneous structural materials, like concrete, have different behavior under tensile stresses in comparison to their behavior under compressive stresses. The aim of this paper is to interpret behavior of such materials subjected to tensile stresses, by using newly introduced concept of fractal geometry. In the first part of this paper, tensile behavior of granular composites has been studied by using fractal geometry. It is shown that the fractality of the cross section in this kind of composites can be used to interpret the size effect on tensile strength. In fact, this work is a modification with innovations on the previous studies on fractal based size effect. This hypothesis... 

    Investigation of vacuum annealing effects on physical-mechanical properties of thermoplastic parts

    , Article Materials and Design ; Volume 26, Issue 1 , 2005 , Pages 89-93 ; 02613069 (ISSN) Ramazani, A ; Mousavi, S ; Sharif University of Technology
    Elsevier Ltd  2005
    Abstract
    Impact and tensile strength of polystyrene and nylon 6 samples, which have been produced by injection molding before and after annealing in different conditions are obtained. Polystyrene samples that are heated on vacuum conditions can deform highly even in temperatures much less than polystyrene glass temperature. This phenomenon is reduced significantly by heating samples to annealing temperature in atmospheric pressure and then removing air from sample environment in constant temperature. Deformation problems for nylon were not so important but due to high temperature implied for annealing of nylon parts, some color change due to oxidative degradation are observed. So for nylon parts a... 

    Recovery of preload in bolted joint using shape memory alloy elements

    , Article 2003 ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Chicago, IL, 2 September 2003 through 6 September 2003 ; Volume 5 C , 2003 , Pages 1843-1849 Ghorashi, M ; Inman, D. J ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2003
    Abstract
    One of the main problems with a bolted joint is losing its preload. In this situation, it cannot provide the required clamping force needed to keep the joint members together or prevent fluid leakages. Although every effort is usually made at the design stage to prevent such failure, because of the numerous factors present in the problem, these efforts are not always successful. After loosening occurs, the joint should be retightened to regain its preload. However, there are circumstances where the joint is very important but it is not easily accessible and retightening cannot be done manually. The shape memory effect (SME) property can be used in such circumstances to produce the necessary... 

    Effects of nano-clay particles on the short-term properties of self-compacting concrete

    , Article European Journal of Environmental and Civil Engineering ; Volume 0 - Issue 0 , Oct , 2015 , Page 1-21 ; 19648189 (ISSN) Hosseini, P ; Afshar, A ; Vafaei, B ; Booshehrian, A ; Molaei Raisi, E ; Esrafili, A ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    Abstract
    The properties of self-compacting concrete (SCC) can be manipulated by the addition of nano-montmorillonite (NMMT) clays. This paper presents the results of an experimental investigation on incorporating small dosages of NMMT clays (.25, .50, .75 and 1.00% addition by mass of total cementitious material) into SCC. Tests were conducted on fresh and hardened specimens to measure workability (by slump flow, V-funnel and L-box), mechanical (by compressive and splitting tensile strengths), durability (electrical resistivity and water penetration) and microstructural (X-ray diffraction and scanning electron microscopy) properties of control and NMMT-reinforced SCCs. The results showed that the... 

    Effects of moisture on warm mix asphalt containing Sasobit

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1866-1873 ; 10263098 (ISSN) Nabizadeh, H ; Naderi, B ; Tabatabaee, N ; Sharif University of Technology
    Sharif University of Technology  2017
    Abstract
    The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA field performance data is limited. This study investigated the susceptibility of Sasobit-modified WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using different concentrations of Sasobit and the... 

    Effects of nano-clay particles on the short-term properties of self-compacting concrete

    , Article European Journal of Environmental and Civil Engineering ; Volume 21, Issue 2 , 2017 , Pages 127-147 ; 19648189 (ISSN) Hosseini, P ; Afshar, A ; Vafaei, B ; Booshehrian, A ; Molaei Raisi, E ; Esrafili, A ; Sharif University of Technology
    Taylor and Francis Ltd  2017
    Abstract
    The properties of self-compacting concrete (SCC) can be manipulated by the addition of nano-montmorillonite (NMMT) clays. This paper presents the results of an experimental investigation on incorporating small dosages of NMMT clays (.25,.50,.75 and 1.00% addition by mass of total cementitious material) into SCC. Tests were conducted on fresh and hardened specimens to measure workability (by slump flow, V-funnel and L-box), mechanical (by compressive and splitting tensile strengths), durability (electrical resistivity and water penetration) and microstructural (X-ray diffraction and scanning electron microscopy) properties of control and NMMT-reinforced SCCs. The results showed that the...