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    On a new approach for finding the kern of a beam section

    , Article Engineering Structures ; Volume 23, Issue 9 , 2001 , Pages 1080-1084 ; 01410296 (ISSN) Mofid, M ; Shadnam, M. R ; McCabe, S. L ; Sharif University of Technology
    2001
    Abstract
    A new approach is presented that can be used to determine the kern of a general arbitrary section with any shape and conditions. The method is simple, practical and powerful, and is based on elementary calculus. Geometries containing curved boundaries and arbitrary shapes can be handled easily with the analytical equations presented, while the numerically specified shape of any other cross-section can also be analyzed by using a numerical form of the exact governing equations developed. The correctness of the results has been ascertained by comparison with analytical solutions, as well as with examples presented in the literature, and very good agreement has been achieved. © 2001 Elsevier... 

    Effect of rolling strain on transformation induced plasticity of austenite to martensite in a high-alloy austenitic steel

    , Article Journal of Materials Processing Technology ; Volume 203, Issue 1-3 , 2008 , Pages 349-354 ; 09240136 (ISSN) Bigdeli Karimi, M ; Arabi, H ; Khosravani, A ; Samei, J ; Sharif University of Technology
    2008
    Abstract
    Current studies show a growing interest on transformation induced plasticity (TRIP) in austenitic steels. Most researches are based on inducing plasticity via tensile stresses, so it seems interesting to accomplish these researches by compressive stresses. Rolling process is a suitable choice to make compressive stresses. In present work, the effects of a wide range of rolling strains (5%-60%) at 0 and 24 °C on the austenite to martensite transformation were investigated on high-alloy austenitic steel. For this purpose, XRD, hardness test and magnetic measurements were used. Results show that by increasing the amount of rolling strain, transformation of austenite to martensite generally... 

    Deformation mechanism of epoxy/clay nanocomposite

    , Article European Polymer Journal ; Volume 43, Issue 3 , 2007 , Pages 782-788 ; 00143057 (ISSN) Akbari, B ; Bagheri, R ; Sharif University of Technology
    2007
    Abstract
    Polymer-layered silicate nanocomposites have been noticed recently due to their outstanding properties. The mechanical properties and deformation mechanism of epoxy/montmorillonite nanocomposites under compressive and flexural loadings were investigated. A reduction in compressive and flexural yield stress and also glass transition temperature with increasing the amount of organoclay was observed. This change in mechanical behavior of epoxy can be explained with observation of plastic deformation mechanism. The study of deformation mechanism revealed that presence of organoclay accelerates shear yielding in epoxy. Microscopic evaluation illustrated that nanoparticles in this system act as... 

    Development of a stress-mode sensitive viscoelastic constitutive relationship for asphalt concrete: experimental and numerical modeling

    , Article Mechanics of Time-Dependent Materials ; 2016 , Pages 1-35 ; 13852000 (ISSN) Karimi, M. M ; Tabatabaee, N ; Jahanbakhsh, H ; Jahangiri, B ; Sharif University of Technology
    Springer Netherlands 
    Abstract
    Asphalt binder is responsible for the thermo-viscoelastic mechanical behavior of asphalt concrete. Upon application of pure compressive stress to an asphalt concrete specimen, the stress is transferred by mechanisms such as aggregate interlock and the adhesion/cohesion properties of asphalt mastic. In the pure tensile stress mode, aggregate interlock plays a limited role in stress transfer, and the mastic phase plays the dominant role through its adhesive/cohesive and viscoelastic properties. Under actual combined loading patterns, any coordinate direction may experience different stress modes; therefore, the mechanical behavior is not the same in the different directions and the asphalt... 

    Development of a stress-mode sensitive viscoelastic constitutive relationship for asphalt concrete: experimental and numerical modeling

    , Article Mechanics of Time-Dependent Materials ; Volume 21, Issue 3 , 2017 , Pages 383-417 ; 13852000 (ISSN) Karimi, M. M ; Tabatabaee, N ; Jahanbakhsh, H ; Jahangiri, B ; Sharif University of Technology
    Springer Netherlands  2017
    Abstract
    Asphalt binder is responsible for the thermo-viscoelastic mechanical behavior of asphalt concrete. Upon application of pure compressive stress to an asphalt concrete specimen, the stress is transferred by mechanisms such as aggregate interlock and the adhesion/cohesion properties of asphalt mastic. In the pure tensile stress mode, aggregate interlock plays a limited role in stress transfer, and the mastic phase plays the dominant role through its adhesive/cohesive and viscoelastic properties. Under actual combined loading patterns, any coordinate direction may experience different stress modes; therefore, the mechanical behavior is not the same in the different directions and the asphalt... 

    Flow stress optimization for 304 stainless steel under cold and warm compression by artificial neural network and genetic algorithm

    , Article Materials and Design ; Volume 28, Issue 2 , 2007 , Pages 609-615 ; 02613069 (ISSN) Mousavi Anijdan, S. H ; Madaah Hosseini, H. R ; Bahrami, A ; Sharif University of Technology
    Elsevier Ltd  2007
    Abstract
    Artificial neural network (ANN) and genetic algorithm were used in this study to obtain a relatively high flow stress in compression tests for 304 stainless steel. Cold and warm compression were carried out in a temperature range from 20 to 600 °C, strain-rate from 0.001 to 100 S-1 and a strain range from 0.1 to 0.5. Optimum conditions for each case were obtained experimentally and were evaluated by the ANN model. The ANN model was used as fitness function for genetic algorithm. The results indicated that this combined algorithm offers an effective condition for 304 stainless steel, which avoids flow localization, dynamic strain aging, adiabatic shear deformation and void generation. © 2005... 

    Experimental evaluation of the effect of residual stress field on crack growth behaviour in C(T) specimen

    , Article Engineering Fracture Mechanics ; Volume 73, Issue 13 , 2006 , Pages 1772-1782 ; 00137944 (ISSN) Farrahi, G. H ; Majzoobi, G. H ; Hosseinzadeh, F ; Harati, S. M ; Sharif University of Technology
    2006
    Abstract
    The effects of the residual stress field resulting from shot peening and the indentation technique were investigated in relation to fatigue crack closure and crack growth behaviour. Compact Specimens of 20NiCrMo2 were used in this investigation. The regions of residual stress field were located behind the fatigue crack tip. Crack closure behaviour was measured with back face strain and crack mouth opening displacement gauges. Crack length was monitored by the compliance and microscopic methods. Residual stress was measured by the incremental hole-drilling method. Subsequently the closure level, propagation rate and resulting crack growth retardation were studied. Crack closure and attendant... 

    Bending analysis of FG-GPLRC axisymmetric circular/annular sector plates by considering elastic foundation and horizontal friction force using 3D-poroelasticity theory

    , Article Composite Structures ; Volume 276 , 2021 ; 02638223 (ISSN) Huo, J ; Zhang, G ; Ghabussi, A ; Habibi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Composite structures encounter different types of imperfections and defects during the installation, working environment, and fabrication process. In the present research, a 3D-poroflexibility theory has been presented to study the bending responses of the functionally graded graphene nanoplatelets reinforced composite (FG-GPLRC) axisymmetric circular/annular sector plates on the elastic substrate. For modeling elastic substrate, horizontal friction force and the elastic foundation with five elastic parameters have been formulated. For obtaining the exact displacement and stress/strain responses of the current structure, a discrete singular convolution integration method (DSC-IM) has been... 

    Compressive behavior of concrete actively confined by metal strips, part B: Analysis

    , Article Materials and Structures/Materiaux et Constructions ; Volume 43, Issue 10 , 2010 , Pages 1383-1396 ; 13595997 (ISSN) Moghaddam, H ; Samadi, M ; Pilakoutas, K ; Sharif University of Technology
    2010
    Abstract
    This paper presents analytical part of an investigation on the application of prestressed strips for concrete confinement. In this paper, an analytical model is proposed to predict the compressive stress-strain curve of strapped concrete as a function of the confinement level. The model was calibrated based on the experimental data of compressive tests which were described in part A of this paper. Various parameters are considered in the proposed model including volumetric ratio, yield strength and ultimate strain of confining material, shape of cross section, strength of plain concrete. Three key points were defined on the stress-stress curve of strapped concrete columns and applied in... 

    Mechanical behavior and texture development of over-aged and solution treated Al-Cu-Mg alloy during multi-directional forging

    , Article Materials Characterization ; Volume 135 , 2018 , Pages 221-227 ; 10445803 (ISSN) Khani Moghanaki, S ; Kazeminezhad, M ; Logé, R ; Sharif University of Technology
    Elsevier Inc  2018
    Abstract
    The effects of initial heat treatments, i.e. solution treating and over ageing, on deformation behavior of an age hardenable Al-Cu-Mg alloy, including mechanical properties and texture evolution, during multi-directional forging (MDF) are investigated. Hardness measurements, electron back scatter diffraction (EBSD) maps, and differential scanning calorimetry (DSC) are carried out. Mechanical behaviors of the alloy in terms of compressive stress and hardness test after MDF are investigated. In both solution treated and over-aged alloys, the compressive stress during MDF shows an increase up to the second pass, and by further straining the flow stress is decreased. However, shear and... 

    On the effect of detwinning-induced plasticity in compressive cyclic loading of NiTi shape memory alloys

    , Article Mechanics of Materials ; Volume 148 , 2020 Ebrahimi, P ; Arghavani, J ; Naghdabadi, R ; McGarry, J. P ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    A new inelastic mechanism, detwinning-induced plasticity (DIP), is proposed to model the response of NiTi SMAs to cyclic loading, based on thermodynamic considerations. DIP is incorporated into a constitutive framework for NiTi SMA. The constitutive framework also includes well-established inelastic mechanisms of phase transformation, transformation-induced plasticity, residual martensite, and detwinning. The model is constructed at the single crystal scale using the framework of thermodynamics and a crystal plasticity formulation. An explicit scale-transition rule is adopted for the simulation of polycrystalline materials, allowing direct comparison of the model predictions with published... 

    3D Bioprinting of oxygenated cell-laden gelatin methacryloyl constructs

    , Article Advanced Healthcare Materials ; Volume 9, Issue 15 , 2020 Erdem, A ; Darabi, M. A ; Nasiri, R ; Sangabathuni, S ; Ertas, Y. N ; Alem, H ; Hosseini, V ; Shamloo, A ; Nasr, A. S ; Ahadian, S ; Dokmeci, M. R ; Khademhosseini, A ; Ashammakhi, N ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    Abstract
    Cell survival during the early stages of transplantation and before new blood vessels formation is a major challenge in translational applications of 3D bioprinted tissues. Supplementing oxygen (O2) to transplanted cells via an O2 generating source such as calcium peroxide (CPO) is an attractive approach to ensure cell viability. Calcium peroxide also produces calcium hydroxide that reduces the viscosity of bioinks, which is a limiting factor for bioprinting. Therefore, adapting this solution into 3D bioprinting is of significant importance. In this study, a gelatin methacryloyl (GelMA) bioink that is optimized in terms of pH and viscosity is developed. The improved rheological properties...