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    Ductility evaluation of confined high-strength concrete flexural members

    , Article Iranian Journal of Science and Technology, Transaction B: Technology ; Volume 25, Issue 1 , 2001 , Pages 129-131 ; 03601307 (ISSN) Khaloo, A. R ; Tariverdilu Asl, S ; Sharif University of Technology
    The influence of concrete strength on the ductility of RC flexural members is investigated. Tests were carried out on beams with three ranges of concrete strengths, and moment-curvature and deflection curves obtained. It is concluded that when the concrete is laterally confined by closed steel ties beams with various levels of concrete strength and very high tensile strength steel exhibit high ductility  

    Influence of confining hoop flexural stiffness on behavior of high-strength lightweight concrete columns

    , Article ACI Structural Journal ; Volume 98, Issue 5 , 2001 , Pages 657-664 ; 08893241 (ISSN) Khaloo, A. R ; Bozorgzadeh, A ; Sharif University of Technology
    This paper presents the behavior of high-strength lightweight concrete columns confined with small size diameter hoop reinforcement. The concrete had a strength of up to 87.2 MPa (12,500 psi). The experimental program consisted of axial load tests on eight column specimens. The cross-sectional shape of the column specimens was elliptical, with dimensions of 152 × 229 mm (6 × 9 in.) and height of 762 mm (30 in.). The only longitudinal reinforcements used were four 4.52 mm (0.178 in.) diameter wires that were tack-welded to the lateral reinforcement to maintain the desired configuration of the lateral reinforcement. The influencing parameters included concrete strength and amount and spacing... 

    Design of a novel HSLA steel with a combination of high strength (140-160 ksi) and excellent toughness

    , Article International Journal of Materials Research ; Volume 112, Issue 10 , 2021 , Pages 800-811 ; 18625282 (ISSN) Nezhad, M. S. A ; Ghazvinian, S ; Amirsalehi, M ; Momeni, A ; Sharif University of Technology
    Walter de Gruyter GmbH  2021
    Three steels were designed based on HSLA-100 with additional levels of Mn, Ni, Cr and Cu. The steels were prepared by controlled rolling and tempered at temperatures in range of 550-700°C. The continuous cooling time curves were shifted to longer times and lower temperatures with the increased tendency for the formation of martensite at lower cooling rates. The microstructures revealed that controlled rolling results in austenite with uniform fine grain structure. The steel with the highest amount of Mn showed the greatest strength after tempering at 750 °C. The top strength was attributed to the formation of Cu-rich particles. The steel with 1.03 wt.% Mn, tempered at 650 °C exhibited the... 

    Reduction of Residual Displacement of Concrete Structures by use of High Strength Rebars

    , M.Sc. Thesis Sharif University of Technology Tazarv, Mostafa (Author) ; Khalu, Alireza (Supervisor)
    Reinforced concrete bridge columns located in regions of high seismicity are designed with large ductility capacity for adequate protection against collapse. This type of design tends to result in large permanent displacements. To maximize post-event operability and to minimize repair costs, new design strategies to reduce these residual displacements are necessary. Even though seismic codes ensure life safety for bridges, large residual displacement after severe earthquake may make the bridge useless. For example, after 1995 Hyogo-ken Nanbu earthquake (Japan), more than 100 reinforced concrete bridge columns experienced a tilt angle of more than 1 degree (1.75% drift). These columns had to... 

    Fracture properties of steel fiber reinforced high strength concrete using work of fracture and size effect methods

    , Article Construction and Building Materials ; Volume 142 , 2017 , Pages 482-489 ; 09500618 (ISSN) Kazemi, M. T ; Golsorkhtabar, H ; Beygi, M. H. A ; Gholamitabar, M ; Sharif University of Technology
    Elsevier Ltd  2017
    This paper deals with investigation of fracture behavior of steel fiber reinforced high strength concrete (SFRHSC) and compare it to plain high strength concrete (HSC). Based on an experimental program, a series of three point bending tests were carried out on 54 notched beams, as recommended by RILEM. The fracture parameters were measured by two methods: work of fracture method (WFM) and size effect method (SEM). Then the fracture parameters obtained from these two methods were compared. The results showed that with increase of steel fibers, fracture energy of GF in WFM and Gf in SEM increase but this increase in work of fracture method is more significant. The effective size of the process... 

    Treatment of bakers yeast wastewater with a Biopack system

    , Article Process Biochemistry ; Volume 37, Issue 5 , 2001 , Pages 447-451 ; 13595113 (ISSN) Nahid, P ; Vossoughi, M ; Alemzadeh, I ; Sharif University of Technology
    The purpose of this study was to investigate the use of a horizontal packed bed bioreactor, named Biopack, to treat high strength wastewater, such as bakers yeast wastewater. The Biopack system (RBCP) is a modified rotating biological contactor and the system was applied for secondary treatment. The RBCP system produced high treatment efficiencies, COD removal was 94.9% when COD was 472 mg/l and surface organic loading = 0.187 kg COD/m2 per day and surface hydraulic loading = 6 l/m2 per day. Variations of surface hydraulic loading from 6 to 11.9 l/m2 per day produced a decrease in COD removal efficiency from 94.9 to 58.6%. Other factors, such as shock load, retention time and rotational... 

    Investigation of Microstructure and Fracture Behavior of Similar and Dissimilar Dual Phase Steels and Martensitic Steel Spot Resistance Welding

    , M.Sc. Thesis Sharif University of Technology Tamizi, Moein (Author) ; Pouranvari, Majid (Supervisor) ; Movahhedi, Mojtaba (Supervisor)
    The new generation of advanced high-strength steels use in the automotive industry cause resistance spot welding study and their failure characteristics during static and dynamic loading are important. In this study, the relationship among microstructure, failure mode and mechanical properties are investigate during similar and dissimilar DP980 and MS1400 jointing advanced high-strength steels resistance spot welding. To search for micro and macro structural changes, the optical microscope, stereographic microscope and scanning electron microscope were used. Micro-hardness test, tensile shear test and Cross tension test to evaluate the mechanical properties were conducted. As well as... 

    Control of hydrogen cracking in the welded steel using microstructural traps

    , Article Materials Science and Technology (United Kingdom) ; Volume 33, Issue 4 , 2017 , Pages 408-414 ; 02670836 (ISSN) Beidokhti, B ; He, P ; Kokabi, A. H ; Dolati, A ; Sharif University of Technology
    Taylor and Francis Ltd  2017
    Hydrogen diffusion into steel can embrittle the material in H2S environments, but this effect can be offset by suitable hydrogen trapping sites in the microstructure. Fine Ti(C,N) inclusions have been studied as the trapping sites in high strength low alloy (API X-70) welds, with Ti additions ranging from 0.004 to 0.16 wt.%. The trapping sites were investigated by electron microscopy and thermal desorption spectroscopy. Manganese sulphide particles were the main initiation sites for hydrogen induced cracking as expected. The optimum Ti addition was around 0.02% with no evidence of cracking in the weld. The estimated values of trapping activation energy for dislocations, microvoids, MnS and... 

    On the effect of ductility of confining material on concrete ductility

    , Article Proceedings of the 2009 Structures Congress - Don't Mess with Structural Engineers: Expanding Our Role, 30 April 2009 through 2 May 2009, Austin, TX ; 2009 , Pages 259-269 ; 9780784410318 (ISBN) Moghaddam, H. A ; Samadi, M ; Sharif University of Technology
    This paper presents the results of an experimental and analytical study on the improvements gained in the axial compressive behavior of confined concrete. Among several parameters affecting compressive ductility of confined concrete, including confinement mechanical volumetric ratio, shape and size effect, number of confinement layers, strength of plain concrete and ductility of confining material, the latter was found to play the most important role in determining the ultimate strain and post peak behavior of concrete. Axial compressive tests were performed on small-scale circular or square section concrete columns, which were retrofitted either by CFRP jacket or by two types of... 

    Influence of four wires tandem submerged arc welding process on heat affected zone properties in high strength pipeline steel

    , Article Proceedings of the 2010 International Conference on Mechanical, Industrial, and Manufacturing Technologies, MIMT 2010, 22 January 2010 through 24 January 2010 ; 2010 , Pages 85-89 ; 9780791859544 (ISBN) Moeinifar, S ; Kokabi, A. H ; Madaah Hosseini, H. R ; Shang, C. J ; Hui, G ; Wei, L. Z ; Sharif University of Technology
    The objective of this investigation was to provide a detailed evaluation of the heat affected zone properties of a high-strength pipeline steel. The X80 high-strength low-alloy microalloyed steel was supplied as a hot rolled plate with accelerated cooling. The four-wire tandem submerged arc welding process with different heat input was used to generate welded joints. The microstructure of the heat affected zone depended on heat input values. M/A constituent appeared in the microstructure of HAZ region for all of the specimens along the prior-austenite grain boundaries and between bainitic ferrite laths. Charpy impact specimens were notched in four locations: FL (fusion line), FL+1mm, FL+2mm... 

    Welding metallurgy of martensitic advanced high strength steels during resistance spot welding

    , Article Science and Technology of Welding and Joining ; Volume 22, Issue 4 , 2017 , Pages 327-335 ; 13621718 (ISSN) Tamizi, M ; Pouranvari, M ; Movahedi, M ; Sharif University of Technology
    The paper addresses the process–microstructure–performance relationships in resistance spot welding of a martensitic advanced high strength steel. Significant softening was observed in the heat affected zone (HAZ) due to allotriomorphic ferrite formation in the inter-critical HAZ and tempering of martensite in sub-critical HAZ (SCHAZ), with the latter plays more important role in mechanical properties of the spot welds. The strain concentration associated with the HAZ softening promotes initiation of pullout failure from the soft SCHAZ. While, the peak load in the interfacial failure mode is governed by the fusion zone size, that of the pullout mode is significantly affected by the HAZ... 

    Understanding the factors controlling the interfacial failure strength of advanced high-strength steel resistance spot welds: hardness vs. fracture toughness

    , Article Science and Technology of Welding and Joining ; Volume 23, Issue 6 , 2018 , Pages 520-526 ; 13621718 (ISSN) Pouranvari, M ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    The failure of advanced high-strength steels’ spot welds is a critical issue for automotive crashworthiness. This paper deals with understanding the underlying factors of the tensile-shear strength of automotive steels’ resistance spot welds during interfacial failure. It was found that the ratio of the fracture toughness to the hardness of the fusion zone is the critical factor governing the interfacial failure mechanism: ductile shear failure (controlled by the fusion zone hardness) vs. cleavage crack propagation (controlled by the fracture toughness). This clarification could pave the way for more accurate modelling of interfacial failure of advanced steel resistance spot welds and shed... 

    Duplex stainless steel/martensitic steel dissimilar resistance spot welding: Microstructure-properties relationships

    , Article Welding Journal ; Volume 98, Issue 9 , 2019 , Pages 263S-272S ; 00432296 (ISSN) Sobhani, S ; Pouranvari, M ; Sharif University of Technology
    American Welding Society  2019
    This paper addresses the phase transformations and mechanical performance of dissimilar resistance spot welds between 2304 duplex stainless steel (DSS) and 1.2-GPa martensitic (MS) advanced high-strength steel (AHSS). The solidification mode and transformation path of the fusion zone (FZ) were analyzed. The key metallurgical feature of the FZ was the formation of a duplex microstructure consisting of delta ferrite and martensite. The FZ size at the sheet/sheet interface was the critical factor controlling the fraction of pullout failure during the partial thickness-partial pullout mode, the load-bearing capacity, and the energy absorption capability of the DSS/MS dissimilar resistance spot... 

    Performance of sustainable high strength concrete with basic oxygen steel-making (BOS)slag and nano-silica

    , Article Journal of Building Engineering ; Volume 25 , 2019 ; 23527102 (ISSN) Zareei, S. A ; Ameri, F ; Bahrami, N ; Shoaei, P ; Moosaei, H. R ; Salemi, N ; Sharif University of Technology
    Elsevier Ltd  2019
    This study presents the results of an experimental evaluation of the performance of high strength concrete (HSC)with basic oxygen steel-making (BOS)slag and nano-silica respectively used as a partial replacement of sand and cement. The properties of fresh and hardened concrete specimens containing 25%, 50%, 75%, and 100% BOS as partial replacement of sand and 2% of cement replaced with nano-silica were evaluated. According to the results, concrete samples containing nano-silica with higher BOS percentages, demonstrated improvements in strength and durability properties, while workability was reduced. For example, at 50% BOS content, about 18% increase in compressive strength and 50%... 

    Friction stir welding of advanced high strength dual phase steel: Microstructure, mechanical properties and fracture behavior

    , Article Materials Science and Engineering A ; Volume 769 , January , 2020 Mahmoudiniya, M ; Kokabi, A. H ; Goodarzi, M ; Kestens, L. A. I ; Sharif University of Technology
    Elsevier Ltd  2020
    In this study, butt welds of an advanced high strength dual phase steel were fabricated using friction stir welding at a constant rotational speed of 800 rpm and different transverse speeds of 100, 150 and 200 mm/min. It was observed that sound welds can be obtained at transverse speeds of 100 and 150 mm/min. At transverse speed of 100 mm/min, the entire stir zone processed at temperatures higher than Ac3. By increasing transverse speed to 150 mm/min, temperature in the bottom region of the stir zone lied between Ac1 and Ac3, while the middle and the top regions experienced temperatures higher than Ac3. The lower peak temperature in the bottom region of the stir zone resulted in finer and... 

    Effects of constrained groove pressing, severe shot peening and ultrasonic nanocrystal surface modification on microstructure and mechanical behavior of S500MC high strength low alloy automotive steel

    , Article Applied Surface Science ; Volume 538 , 2021 ; 01694332 (ISSN) Karademir, I ; Celik, M. B ; Husem, F ; Maleki, E ; Amanov, A ; Unal, O ; Sharif University of Technology
    Elsevier B.V  2021
    S500MC high strength low alloy automotive steel is exposed to bulk severe plastic deformation (SPD) via constrained groove pressing (CGP) and surface severe plastic deformation (S2PD) via severe shot peening (SSP) and ultrasonic nanocrystal surface modification (UNSM). SSP and UNSM could create a nanocrystallization layer till 50–100 µm away from outmost surface. EBSD investigations showed average nano-grain size obtained via SSP and UNSM was found to be below 100 nm regime. The strength was improved via 1st to 4th pass of CGP, but elongation percentage decreased abruptly. UNSM achieves both strength-ductility improvement with gradient structure. SSP improves the total elongation however a... 

    Effect of Nickel and Manganese on Weld Microstructure and Mechanical Properties in Shielded Metal arc Welded HSLA-X80

    , M.Sc. Thesis Sharif University of Technology Sheykh Jaberi, Fariba (Author) ; Kokabi, Amir Hossein (Supervisor) ; Maddah Hosseini, Hamid Reza (Supervisor)
    Microstructure and mechanical properties developments of X80 weld metal by addition of different amounts of alloying elements such as: Nickel and Manganese in coated electrodes were investigated. For this reason samples were welded by electrodes that Ni value has been changed between 0.8%- 3.2% in tow critical amounts of Mn: 0.7 and 1.6. The weld quality was evaluated using nondestructive testing methods (NDT), such as visual inspection and radiography. Tensile test, Charpy impact test and microhardness results indicated the suitable range of Ni and Mn for achieving acceptable mechanical properties. In addition, optical microscopy and scanning electron microscopy (SEM) were applied to link... 

    The Evaluation of Microstructure and Mechanical Properties of a HSHR Stainless Steel Strengthen by Nano-Precipitates

    , Ph.D. Dissertation Sharif University of Technology Attarian, Mitra (Author) ; Karimi Taheri, Ali (Supervisor) ; Davami, Parviz (Co-Advisor)
    In this research, a computational method based on thermodynamic and physical metallurgy coupled by the d-electron approach was used to design the composition of a high strength and heat resistant (HSHR) stainless steel. Then, three series of the heat resistant 25Cr-35Ni-Nb (HP-Nb) stainless steels with tungsten, nitrogen, and micro alloying elements additions were cast. In these alloys a Nb/(C+ 6/7 N) ratio of ≈ 2.4 to 3.7 was chosen and they were directionally solidified under two cooling rates of 23 Ks-1 and 6 Ks-1. The effects of the alloy chemical composition and solidification cooling rate on the macrostructure, microstructure, microsegregation, and inclusions in the alloys were... 

    Development of Submicron/Nanostructured HSLA Steel Using Thermomechanical Treatment

    , M.Sc. Thesis Sharif University of Technology Afrasiabi, Yaser (Author) ; Karimi Tahri, Ali (Supervisor)
    Nanocrystalline steel was developed by severe cold-rolling and subsequent annealing of HSLA steel with an original microstructure of lath martensite. Specimens are austenitized at 1000 ºC for 30 min followed by quenching in brine. The quenched specimens are cold rolled with 80% to 90 % reduction and then annealed at temperatures from 400 to 700ºC for 10 to 120 min.The specimens annealed at temperature 500oC for 60 min showed the multiphased ultrafine structure composed of equiaxed ultrafine ferrite grains with the mean grain size of 180 nm, nano-carbides distributed uniformly and blocks of tempered martensite. The produced nanostructured steel exhibited a yield stress and UTS, of 1280 MPa... 

    Investigation on adult occupant protection in car pole side impact using various material and thickness of side doors and B pillar

    , Article Applied Mechanics and Materials ; Vol. 663, issue , 2014 , p. 579-584 Lilehkoohi, A. H ; Faieza, A. A ; Sahari, B. B ; Halali, M ; Sharif University of Technology
    In this paper the objective is to study the effect of the material and thickness of the side doors and B pillar on crashworthiness and the energy absorbed in order to select a proper material and an optimized thickness to approach a five star car concept based on the Euro New Car Assessment Program (Euro-NCAP) testing Pole Side Impact. In this matter, four materials and five thicknesses have been chosen for the vehicle model and a total of twenty simulations have been conducted. The results showed that the best selected materials and thicknesses were high strength Steel 204M with a thickness of 1.2mm for side doors and 0.65mm for the B pillar, however, it is important to note that this...