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    Notch-texture strengthening mechanism in commercially pure titanium thin sheets

    , Article Materials and Design ; Vol. 55, issue , March , 2014 , p. 683-689 Nasiri-Abarbekoh, H ; Abbasi, R ; Ekrami, A ; Ziaei-Moayyed, A. A ; Sharif University of Technology
    Simultaneous effects of notch and texture on strengthening mechanisms of rolled thin sheets of commercially pure titanium were investigated. The presence of notch led to the restriction of deformation systems and different fracture behaviors compared to un-notched specimens. The loss of material's ability to accommodate plastic deformation at the notch tip with increase in rolling reductions changed the notch strengthening phenomenon to the notch weakening one. At medium levels of deformation, due to the simultaneous development of a triaxial stress state and strong basal texture at the notch tip, a new strengthening mechanism which is called "notch-texture strengthening mechanism" led to a... 

    A study on the axial stresses of P-FGM, SFGM and E-FGM plates under pressure loading using the energy concept

    , Article 27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010, 19 September 2010 through 24 September 2010, Nice ; Volume 3 , 2010 , Pages 2060-2068 ; 9781617820496 (ISBN) Dastoom Laatleyli, H ; Abedian, A ; Sharif University of Technology
    In this study the energy concept along with the classical plate theory (CPT), first and third order shear deformation theories (FSDT and TSDT) are used to predict the large deflection and through the thickness stresses of a FGM plate. For defining the volume fraction of the FGM constituent materials three different functions are considered; simple power-law (PFGM), exponential (E-FGM) and sigmoid (S_FGM) functions. Power-law and exponential functions are commonly used tocontrol the variations of properties of FGMs. However, with both functions, a stress concentration appears due to abruptchange of the volume fraction of the constituents. Therefore, a sigmoid FGM is used to define a new... 

    The axial and lateral behavior of low strength concrete confined by GFRP wraps: an experimental investigation

    , Article Structures ; Volume 27 , October , 2020 , Pages 747-766 Khaloo, A ; Tabatabaeian, M ; Khaloo, H ; Sharif University of Technology
    Elsevier Ltd  2020
    The purpose of this investigation is to investigate the axial and lateral behavior of low strength concrete confined by glass fiber reinforced polymer (GFRP) wraps. A total of 48 cylindrical samples having 150 mm diameter and 300 mm height were strengthened and examined. The mix designs were provided with four different target strength (5, 10, 15, and 20 MPa). The axial and lateral strain were studied to evaluate the axial strain relation and the lateral strain for axial compression. The results of this investigation present a comparison between the nine models previously reported for normal strength concrete and the lesser-known context of low strength concrete confined by fiber reinforced... 

    Energy absorption of the strengthened viscoelastic multi-curved composite panel under friction force

    , Article Archives of Civil and Mechanical Engineering ; Volume 21, Issue 4 , 2021 ; 16449665 (ISSN) Shao, Y ; Zhao, Y ; Gao, J ; Habibi, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    This study investigated FG carbon nanotubes filled composites, which are promising metamaterials that can be useful in the energy absorption field. This structure can absorb energy through elastic deformation. For this issue, absorbed energy and dynamic stability analysis of the FG-CNTRC curved panel surrounded by a non-polynomial viscoelastic substrate using three-dimensional poroelasticity theory is investigated. For stability of the structure after vibrating, the viscoelastic substrate as the non-polynomial viscoelastic model is presented. The curved panel comprises multilayer carbon nanotubes (CNT) which are uniformly distributed in all layers of facing sheets; however, the system’s... 

    Casing Design Optimization Considering Drilling and Production Conditions

    , M.Sc. Thesis Sharif University of Technology Sadeghi, Mahdi (Author) ; Jamshidi, Saeed (Supervisor) ; Shad, Saeed (Supervisor)
    Casing design is one of the most expensive parts in the drilling of oil wells, and any cost reduction with the basic design of these casing strings will significantly reduce the total cost of the operation. In recent years, occurring scenarios-based casing design has become popular; Because in many cases, it eliminates non-occurring scenarios such as gas kick and saves on drilling costs. In this study, we have tried to investigate all scenarios that may occur during the lifetime of the well, whether drilling or production, and for each well, based on its own field information, possible scenarios for each casing part are selected separately and the applying loads are calculated. For this... 

    Effects of thickness and texture on mechanical properties anisotropy of commercially pure titanium thin sheets

    , Article Materials and Design ; Volume 44 , February , 2013 , Pages 528-534 ; 02641275 (ISSN) Nasiri Abarbekoh, H ; Ekrami, A ; Ziaei Moayyed, A. A ; Sharif University of Technology
    Simultaneous effects of thickness and texture on the anisotropy of mechanical properties and fracture behaviors of commercially pure titanium thin sheets were studied. The activation of different deformation systems, due to the split distribution of basal texture, led to mechanical properties anisotropy. The crack initiation and propagation energies, when the loading direction was parallel to the initial rolling direction, decreased with increasing thickness ranges from 0.25 to 1 mm. The changes of size, shape and distribution of dimples with increasing thickness confirmed the restriction of deformation systems and the development of triaxial stress state and plane-strain condition at the... 

    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... 

    Study of Shear Lag Effect on Non-rectangular RC Shear Walls

    , M.Sc. Thesis Sharif University of Technology Tabiee, Mohammad (Author) ; Khaloo, Alireza (Supervisor)
    The present study aims to evaluate the effect of the shear-lag on non-rectangular RC shear walls and develop equations to determine the axial stress and strain distributions and calculate the effective flange width. Research has shown that a non-rectangular shear wall under a lateral load experiences the largest axial stress and strain in the flange-web cojunction. This phenomenon is referred to as the shear-lag effect and reduces the bending capacity of the shear wall. As a result, the effective flange width is typically defined to consider the shear lag effect. The present work first reviewed the literature on the effects of shear lag on non-rectangular RC shear walls. Then, flanged shear... 

    Analytic solutions to the oscillatory behavior and primary resonance of electrostatically actuated microbridges

    , Article International Journal of Structural Stability and Dynamics ; Volume 11, Issue 6 , December , 2011 , Pages 1119-1137 ; 02194554 (ISSN) Mojahedi, M ; Zand, M. M ; Ahmadian, M. T ; Babaei, M ; Sharif University of Technology
    In this paper, the vibration and primary resonance of electrostatically actuated microbridges are investigated, with the effects of electrostatic actuation, axial stress, and mid-plane stretching considered. Galerkin's decomposition method is adopted to convert the governing nonlinear partial differential equation to a nonlinear ordinary differential equation. The homotopy perturbation method (a special case of homotopy analysis method) is then employed to find the analytic expressions for the natural frequencies of predeformed microbridges, by which the effects of the voltage, mid-plane stretching, axial force, and higher mode contribution on the natural frequencies are studied. The primary... 

    Biomechanical response of intact, degenerated and repaired intervertebral discs under impact loading – Ex-vivo and In-Silico investigation

    , Article Journal of Biomechanics ; Volume 70 , March , 2018 , Pages 26-32 ; 00219290 (ISSN) Nikkhoo, M ; Wang, J. L ; Parnianpour, M ; El-Rich, M ; Khalaf, K ; Sharif University of Technology
    Elsevier Ltd  2018
    Understanding the effect of impact loading on the mechanical response of the intervertebral disc (IVD) is valuable for investigating injury mechanisms and devising effective therapeutic modalities. This study used 24 porcine thoracic motion segments to characterize the mechanical response of intact (N = 8), degenerated (Trypsin-denatured, N = 8), and repaired (Genepin-treated, N = 8) IVDs subject to impact loading. A meta-model analysis of poroelastic finite element simulations was used in combination with ex-vivo creep and impact tests to extract the material properties. Forward analyses using updated specimen-specific FE models were performed to evaluate the effect of impact duration. The...