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    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.... 

    Study on dynamic and mechanical characteristics of carbon fiber- and polyamide fiber-reinforced seismic isolators

    , Article Materials and Structures/Materiaux et Constructions ; Volume 47, Issue 3 , March , 2014 , Pages 447-457 ; ISSN: 13595997 Bakhshi, A ; Jafari, M. H ; Valadoust Tabrizi, V ; Sharif University of Technology
    Abstract
    Seismic isolators are used to decrease the energy and forces of earthquakes. The weight of conventional steel-reinforced elastomeric isolators (SREIs) is high, mostly due to the use of multiple steel shim plates. On the contrary, the damping ratio of SREIs is relatively low. Accordingly, this research utilizes a new approach in which the steel shim plates are replaced by carbon and polyamide fibers. This study attempts to obtain the dynamic and mechanical properties of such carbon fiber- and polyamide fiber-reinforced elastomeric isolators, in comparison with SREIs. In this work, a number of specimens were initially designed and manufactured. Afterwards, compression and cyclic shear tests... 

    The optimum combination of tool rotation rate and traveling speed for obtaining the preferable corrosion behavior and mechanical properties of friction stir welded AA5052 aluminum alloy

    , Article Materials and Design ; Volume 50 , 2013 , Pages 620-634 ; 02613069 (ISSN) Bagheri Hariri, M ; Gholami Shiri, S ; Yaghoubinezhad, Y ; Mohammadi Rahvard, M ; Sharif University of Technology
    Elsevier Ltd  2013
    Abstract
    This study attempts to find an optimum combination of the welding tool rotation rate (ω) and traveling speed (υ), concerning the corrosion and mechanical properties of Friction Stir Welded (FSWed) AA5052 Aluminum alloy. The effect of the tool speeds on the FSWed AA5052 are investigated via potentiodynamic polarization, open circuit potential (OCP) monitoring, test of the susceptibility to intergranular corrosion, weight loss, tension and micro-hardness tests. Optical microscope and Scanning Electron Microscopy (SEM) were employed for studying the morphology and analyzing the probable intergranular attacks. It was found that by increasing υ up to 200. mm/min at ω=400 rpm, the microstructural... 

    Dynamic simulation of the biped normal and amputee human gait

    , Article Mobile Robotics: Solutions and Challenges - Proceedings of the 12th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2009, 9 September 2009 through 11 September 2009, Istanbul ; 2010 , Pages 1113-1120 ; 9814291269 (ISBN) ; 9789814291262 (ISBN) Shandiz, M. A ; Farahmand, F ; Zohour, H ; Sharif University of Technology
    2010
    Abstract
    A two-dimensional seven link biped dynamic model was developed to investigate the mechanical characteristics of the normal and amputee locomotion during the complete gait cycle. The foot-ground contact was simulated using a five-point penetration contact model. The equations of motion were derived using Lagrange method. Optimization of the normal human walking model provided constant coefficients for the driving torque equations that could reasonably reproduce the normal kinematical pattern. The resulting torques were then applied to the intact joints of the amputee model with a prosthetic leg equipped with a kinematical driver controller for the ankle and either a hydraulic, elastic or... 

    On the mechanical characteristics of graphene nanosheets: A fully nonlinear modified Morse model

    , Article Nanotechnology ; Volume 31, Issue 11 , 2020 Shoghmand Nazarloo, A ; Ahmadian, M ; Firoozbakhsh, K ; Sharif University of Technology
    Institute of Physics Publishing  2020
    Abstract
    In this paper, the mechanical properties of graphene nanosheets are evaluated based on the nonlinear modified Morse model. The interatomic interactions including stretching and bending of the covalent bonds between carbon atoms, are replaced by nonlinear extensional and torsional spring-like elements. The finite element method is implemented to analyze the model under different loading conditions and linear characteristics of the graphene structure including the Young's modulus, surface modulus, shear modulus and Poisson's ratio are evaluated for various geometries and chirality where these properties are shown to be size and aspect ratio dependent. It is also found that when the dimensions... 

    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... 

    Improving the mechanical characteristics of semi-rigid saddle connections

    , Article Journal of Constructional Steel Research ; Volume 186 , 2021 ; 0143974X (ISSN) Moghaddam, H ; Sadrara, A ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    There are many steel structures in Iran with semi-rigid saddle connections. It has been observed that, during a strong earthquake, this type of connection can experience a premature fracture, which will endanger the stability of the structure. The present study endeavored to improve the mechanical characteristics including the initial stiffness, yield moment, maximum moment, crack rotation, and load transfer mechanisms of the conventional saddle connections using retrofitting methods. An experimental study was conducted on six full-scale specimens to study the effect of the retrofitting methods on the stiffness, yield moment, and maximum moment of the connection and for the prevention of... 

    Fracture characterization from noisy displacement data using artificial neural networks

    , Article Engineering Fracture Mechanics ; Volume 271 , 2022 ; 00137944 (ISSN) Khaleghi, M ; Haghighat, E ; Vahab, M ; Shahbodagh, B ; Khalili, N ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Mechanical characterization of fractures, i.e., identifying their characteristic parameters such as energy release rate, is crucial to assess the safety and stability of structural members. This is generally achieved using a combination of finite element analysis and optimization. Machine learning models are increasingly used to characterize engineering problems. While such models have shown impressive performance on smooth data, their performance diminishes significantly on data with discontinuities and sharp gradients. For fractures, this issue is more severe due to the singular solutions in the vicinity of the fracture tips. To resolve this difficulty, leveraging classical fracture... 

    Experimental and numerical evaluation of the mechanical characteristics of semi-rigid saddle connections

    , Article Structural Design of Tall and Special Buildings ; Volume 31, Issue 7 , 2022 ; 15417794 (ISSN) Moghaddam, H ; Sadrara, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2022
    Abstract
    Saddle connections are semi-rigid connections that are widely used in Iran. Many existing buildings contain this type of connection. The present study conducted full-scale experiments and used extensive numerical modeling to study the mechanical characteristics of saddle connections. The mechanical characteristics examined were the moment-transfer mechanism, initial stiffness, yield moment, maximum moment, and fracture rotation. The configuration and dimensions of the experimental and numerical specimens were chosen to be similar to those of saddle connections in existing buildings. A parametric study was conducted to determine the factors affecting the mechanical characteristics of these... 

    Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

    , Article Materials Science and Engineering A ; Vol. 608, issue , 2014 , pp. 35-45 ; ISSN: 09215093 Sarkari Khorrami, M ; Mostafaei, M. A ; Pouraliakbar, H ; Kokabi, A. H ; Sharif University of Technology
    Abstract
    In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic-martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain... 

    Evaluating the effects of different plasticizers on mechanical properties of starch/ clay nanocomposites

    , Article Advanced Materials Research ; Volume 829, 2014 , 2014 , Pages 279-283 ; ISSN: 10226680 ; ISBN: 9783037859070 Sherafati, M ; Mousavi, S. M. A ; Emam Djomeh, Z ; Bagheri, R ; Sharif University of Technology
    Abstract
    Nano-biocomposites are a new class of hybrid materials composed of nano-sized filler (nanofiller) incorporated into a bio-based matrix. Such an association between eco-friendly biopolymers and nano-objects, with the aim to obtain synergic effects, is one of the most innovating routes to enhance the properties of these bio-matrices. In recent years, there has been an increasing interest in Starch as an inexpensive and renewable source has been used as a filler for environmentally friendly plastics for about two decades. However, the poor mechanical properties of starch based biopolymers, leads to use of nanoparticles as reinforcing materials. In the present study, the influence of a... 

    Impact of stripe unit size on performance and endurance of SSD-based RAID arrays

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1978-1998 ; 10263098 (ISSN) Salmasi, F. R ; Asadi, H ; GhasemiGol, M ; Sharif University of Technology
    Sharif University of Technology  2013
    Abstract
    Over the past decades, Redundant Array of Independent Disks (RAIDs) have been configured based on mechanical characteristics of Hard Disk Drives (HDDs). With the advent of Solid-State Drives (SSDs), configurations such as stripe unit size can be far from the characteristics of SSDs. In this paper, we investigate the effect of stripe unit size on the endurance and the overall I/O performance of an SSD-based RAID array and compare the optimal stripe unit size with the suggested stripe unit sizes for HDD-based RAID. To this end, we first examine the number of extra page reads and writes imposed by write requests, and then observe the corresponding impact on the overall throughput and the... 

    FEM analysis of single grit chip formation in creep-feed grinding of Inconel 718 superalloy

    , Article Advanced Materials Research, 18 September 2011 through 21 September 2011, Stuttgart ; Volume 325 , 2011 , Pages 128-133 ; 10226680 (ISSN) ; 9783037852316 (ISBN) Zahedi, A ; Akbari, J ; Sharif University of Technology
    2011
    Abstract
    Recent advances in materials science have necessitated the development and understanding of manufacturing processes for safe and repeatable utilization. Grinding is shown to be a promising material removal process especially for brittle and hard to cut materials such as superalloys. Grinding has always been associated with analysis and modeling complications regarding its nature which has limited its extension and reliability of use. The first step in analysis of grinding is considering the action of a single abrasive grit on workpiece surface. In this work the action of a single CBN abrasive grit in creep-feed grinding process of Inconel 718 superalloy is modeled and analyzed using a 3D FEM... 

    Comprehensive study on the effect of SiC and carbon additives on the pressureless sintering and microstructural and mechanical characteristics of new ultra-high temperature ZrB2 ceramics

    , Article Ceramics International ; Volume 41, Issue 9, Part A , November , 2015 , Pages 11456–11463 ; 02728842 (ISSN) Khoeini, M ; Nemati, A ; Zakeri, M ; Tamizifar, M ; Samadi, H ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    The combined effects of SiC and carbon additives on the densification, structure and characteristics of pressureless sintered ZrB2-SiC ceramic composites were studied. The ZrB2-SiC (1-10wt%) composite powders were mixed by 1-2wt% carbon. The prepared powder mixtures were then cold-consolidated and sintered in argon environment in the temperature range of 1800-2100°C for 2h. The constituted phases and microstructural evolutions were studied using x-ray diffraction and scanning electron microscope equipped with an energy dispersive x-ray detector. The obtained results concluded that the densification was increased by extending the sintering time and also by prior holding... 

    Reactive friction stir processing of AA 5052-TiO2 nanocomposite: Process-microstructure-mechanical characteristics

    , Article Materials Science and Technology (United Kingdom) ; Volume 31, Issue 4 , 2015 , Pages 426-435 ; 02670836 (ISSN) Khodabakhshi, F ; Simchi, A ; Kokabi, A. H ; Sadeghahmadi, M ; Gerlich, A. P ; Sharif University of Technology
    Maney Publishing  2015
    Abstract
    Friction stir processing (FSP) is a solid state route with a capacity of preparing fine grained nanocomposites from metal sheets. In this work, we employed this process to finely distribute TiO2 nanoparticles throughout an Al-Mg alloy, aiming to enhance mechanical properties. Titanium dioxide particles (30 nm) were preplaced into grooves machined in the middle of the aluminium alloy sheet and multipass FSP was afforded. This process refined the grain structure of the aluminium alloy, distributed the hard nanoparticles in the matrix and promoted solid state chemical reactions at the interfaces of the metal/ceramic particles. Detailed optical and electron microscopic studies showed that the... 

    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... 

    Improving the mechanical behavior of the adhesively bonded joints using RGO additive

    , Article International Journal of Adhesion and Adhesives ; Volume 70 , 2016 , Pages 277-286 ; 01437496 (ISSN) Marami, G ; Adib Nazari, S ; Faghidian, S. A ; Vakili Tahami, F ; Etemadi, S ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    In this research, Araldite 2011 has been reinforced using different weight fractions of Reduced Graphene Oxide (RGO). Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses were conducted and it has been shown that introduction of the RGO greatly changes the film morphology of the neat adhesive. Uni-axial tests were carried out to obtain the mechanical characteristics of the adhesive-RGO composites. It has been observed that introducing 0.5 wt% RGO enhances the ultimate tensile strength of the composites by 30%. In addition, single lap joints using neat adhesive and adhesive-RGO composites were fabricated to... 

    Microstructural and mechanical characteristics of hybrid SiC/Cu composites with nano- and micro-sized SiC particles

    , Article Ceramics International ; 2018 ; 02728842 (ISSN) Akbarpour, M. R ; Mousa Mirabad, H ; Alipour, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Hybrid Cu-SiC composites have been highly considered in order to achieve a combination of electrical and thermal properties along with high strength and wear resistance. However, limited investigations have ever been conducted over the effects of using hybrid (combination of nano and micro size) particles on the wear resistance behavior of these composites. Hence, in the present study, Cu-SiC nanocomposite with 4 vol% nanosize and 4 vol% microsize SiC, and Cu-SiC microcomposite with 8 vol% micro- SiC were fabricated through mechanical milling and hot pressing process. Results revealed the homogeneous dispersion of SiC particles in the matrix, high densification, and ultrafine-grain matrix... 

    Vibrational analysis of single-walled carbon nanotubes using beam element

    , Article Thin-Walled Structures ; Volume 47, Issue 6-7 , 2009 , Pages 646-652 ; 02638231 (ISSN) Sakhaee Pour, A ; Ahmadian, M. T ; Vafai, A ; Sharif University of Technology
    2009
    Abstract
    Vibrational analysis of single-walled carbon nanotubes (SWCNTs) is performed using a finite element method (FEM). To this end, the vibrational behavior of bridge and cantilever SWCNTs with different side lengths and diameters is modeled by three-dimensional elastic beams and point masses. The beam element elastic properties are calculated by considering mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice. The mass of each beam element is assumed as point masses at nodes coinciding with the carbon atoms. Implementing the atomistic simulation approach, the natural frequencies of zigzag and armchair SWCNTs are computed. It is observed that the... 

    Microstructural and mechanical characteristics of hybrid SiC/Cu composites with nano- and micro-sized SiC particles

    , Article Ceramics International ; Volume 45, Issue 3 , 2019 , Pages 3276-3283 ; 02728842 (ISSN) Akbarpour, M. R ; Mousa Mirabad, H ; Alipour, S ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    Hybrid Cu-SiC composites have been highly considered in order to achieve a combination of electrical and thermal properties along with high strength and wear resistance. However, limited investigations have ever been conducted over the effects of using hybrid (combination of nano and micro size) particles on the wear resistance behavior of these composites. Hence, in the present study, Cu-SiC nanocomposite with 4 vol% nanosize and 4 vol% microsize SiC, and Cu-SiC microcomposite with 8 vol% micro- SiC were fabricated through mechanical milling and hot pressing process. Results revealed the homogeneous dispersion of SiC particles in the matrix, high densification, and ultrafine-grain matrix...