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    On the influence of deformation rate and cooling media on the static strain aging of a warm-rolled low carbon steel

    , Article International Journal of Material Forming ; Volume 6, Issue 3 , February , 2013 , Pages 417-422 ; 19606206 (ISSN) Koohbor, B ; Ohadi, D ; Sharif University of Technology
    An investigation was performed on the static strain aging behavior of warm-rolled low carbon steel during a nearly 1-year aging period, from the view point concerning with influence of changing the deformation speed and cooling media. Mechanical response of the examined material during aging period was evaluated through variations occurred in strength and hardness of the warm-deformed steel. It was shown that changing the rolling speed as well as cooling rate, may result in the occurrence of different metallurgical phenomena, consequently altering the aging kinetics of the material. It was also found that by increasing rolling speed, an increase in the value of hardness and UTS takes place,... 

    Study on effect of residual stress distributions on kinetics of static strain aging after cold rolling

    , Article Materials Science and Technology ; Volume 27, Issue 11 , 2011 , Pages 1620-1626 ; 02670836 (ISSN) Koohbor, B ; Serajzadeh, S ; Sharif University of Technology
    In the present research, the effect of residual stress distribution on the static strain aging (SSA) phenomenon in cold rolled steel was investigated. A three-dimensional model was employed to evaluate the residual stress distributions within the rolled strips, and hole drilling experiments were also performed to verify the data obtained from the mathematical model. Hardness and tensile tests were then performed on the cold rolled samples at different temperatures and aging periods, and the results of these tests were utilised to assess SSA behaviour after different rolling programs. The results show that SSA occurs within the cold rolled steel in the employed aging period, and its kinetics... 

    Kinetics of static strain aging after temper rolling of low carbon steel

    , Article Ironmaking and Steelmaking ; Volume 38, Issue 4 , 2011 , Pages 314-320 ; 03019233 (ISSN) Koohbor, B ; Serajzadeh, S ; Sharif University of Technology
    In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses... 

    Study on static strain aging of 6082 aluminium alloy

    , Article Materials Science and Technology ; Volume 26, Issue 2 , Jul , 2010 , Pages 169-175 ; 02670836 (ISSN) Dadbakhsh, S ; Karimi Taheri, A ; Sharif University of Technology
    In this study both the quench aging and static strain aging kinetics of a 6082 Al alloy were investigated at a temperature range of 130-200°C using the Vickers hardness and tensile test. The activation energy and dislocation density were determined at different stages of the aging phenomenon. The former was used to analyse the kinetics of aging and the latter to interpret the competition of strengthening and recovery mechanisms during aging. It is shown that different activation energies are achieved depending on the aging time and temperature relating to formation of appropriate precipitates at different stages of aging. Moreover, it is revealed that prestrain reduces the activation energy.... 

    Investigation of Multistage Static Strain Aging of Low Carbon Steel using Rolling Pre-strain

    , M.Sc. Thesis Sharif University of Technology Rizehvandy, Siroos (Author) ; karimi taheri, Ali (Supervisor)
    In the present study, multistage strain aging phenomenon using rolling pre-strain and solution treatment at 680℃ for 40 min was used to study the effect of temperature and inter-pass time (IPT) on the static strain aging behavior of a low carbon steel sheet. The increase in hardness and strength caused by work hardening and the aging at each pass were separately calculated.The samples were rolled and subjected to aging process both in a single pass of 20% rolling reduction in thickness and in four stages consisted of 5% reduction at each stage. The mechanical properties of the samples aged at different time and temperature, were compared. In order to evaluate the effects of pre-strain type,... 

    Influence of deformation path change on static strain aging of cold rolled steel strip

    , Article International Journal of Advanced Manufacturing Technology ; Volume 61, Issue 9-12 , 2012 , Pages 901-909 ; 02683768 (ISSN) Koohbor, B ; Serajzadeh, S
    Effect of deformation path change on the static strain aging of low carbon steel was studied in this work. In the first stage, strip samples were subjected to cold rolling processes under different paths with the same total reduction in thickness while the deformation behaviors of the rolled samples were also evaluated using a mathematical analysis. Then, cold-rolled strips were aged in room temperature up to 45 days while hardness and tensile evaluations were performed to assess the mechanical properties of the as-rolled and the aged samples. Finally, the influence of rolling pass schedule on the subsequent strain aging phenomenon was investigated by means of the experimental results and... 

    A size-dependent nonlinear Timoshenko microbeam model based on the strain gradient theory

    , Article Acta Mechanica ; Volume 223, Issue 6 , 2012 , Pages 1233-1249 ; 00015970 (ISSN) Asghari, M ; Kahrobaiyan, M. H ; Nikfar, M ; Ahmadian, M. T ; Sharif University of Technology
    The geometrically nonlinear governing differential equations of motion and the corresponding boundary conditions are derived for the mechanical analysis of Timoshenko microbeams with large deflections, based on the strain gradient theory. The variational approach is employed to achieve the formulation. Hinged-hinged beams are considered as an important practical case, and their nonlinear static and free-vibration behaviors are investigated based on the derived formulation  

    Effect of rolling speed on the occurrence of strain aging during and after warm rolling of a low-carbon steel

    , Article Journal of Materials Science ; Volume 45, Issue 13 , July , 2010 , Pages 3405-3412 ; 00222461 (ISSN) Koohbor, B ; Ohadi, D ; Serajzadeh, S ; Akhgar, J. M ; Sharif University of Technology
    In this study, effect of rolling speed on strain aging phenomena in warm rolling of a carbon steel has been investigated. For this purpose, by using a mathematical model and predicting temperature and strain rate fields, the possibility of occurrence of dynamic strain aging during the warm rolling was first evaluated. In the next stage, warm-rolled samples were aged up to 11 months at room temperature for studying the kinetics of static strain aging, while mechanical tests as well as microstructural evolutions have been performed to determine the effect of strain aging on material behavior. The results indicate that dynamic strain aging may not occur for the employed rolling program;... 

    Mechanical characterization of brain tissue in compression

    , Article ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 21 August 2016 through 24 August 2016 ; Volume 3 , 2016 ; 9780791850138 (ISBN) Shafiee, A ; Ahmadian, M. T ; Hoviat Talab, M ; Computers and Information in Engineering Division; Design Engineering Division ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    The biomechanical behavior of brain tissue is needed for predicting the traumatic brain injury (TBI). Each year over 1.5 million people sustain a TBI in the United States. The appropriate coefficients for modeling the injury prediction can be evaluated using experimental data. In the present paper, using an experimental setup on bovine brain tissue, unconfined compression tests at quasi-static strain rates of ϵ 0.0004s-1, 0.008s-1 and 0.4s-1 combined with a stress relaxation test under unconfined uniaxial compression with ϵ 0.67s-1 ramp rate are performed. The fitted viscohyperelastic parameters were utilized by using obtained stressstrain curves. The finite element analysis (FEA) is... 

    A novel phenomenological constitutive model for Ti-6Al-4V at high temperature conditions and quasi-static strain rates

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 235, Issue 13 , 2021 , Pages 1831-1842 ; 09544100 (ISSN) Ashrafian, M. M ; Hosseini Kordkheili, A ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Phenomenological constitutive modeling of Ti-6Al-4V at temperatures between 923 and 1023 K under 0.0005–0.05 s−1 quasi-static rates is studied based on a phenomenological approach. For this purpose, the Johnson–Cook constitutive model is revisited. At low temperature conditions under moderate to high strain rates, the material’s stress–strain curves are the most similar to power-law function. Contrary to this, at high temperature conditions under low to moderate strain rates, the saturation-type function well describes the stress–strain curves. On the other hand, it is illustrated that the Johnson–Cook constitutive model is feeble to predict the material’s behavior correctly. Accordingly, in... 

    A rate-dependent constitutive equation for 5052 aluminum diaphragms

    , Article Materials and Design ; Vol. 60, Issue 1 , 2014 , pp. 13-20 ; ISSN: 02613069 Hosseini Kordkheili, S. A ; Ashrafian, M. M ; Toozandehjani, H ; Sharif University of Technology
    In this article, both experimental and numerical approaches are conducted to present a constitutive equation for 5052 aluminum diaphragms under quasi-static strain rate loadings. For this purpose the stress-strain curves at different strain rates are obtained using tensile tests. Brittle behavior during tensile tests is observed due to samples thin thicknesses. Employing Johnson-Cook constitutive equation no yields in reasonable agreement with these tensile tests results. Therefore, developing a more suitable constitutive equation for aluminum diaphragms is taken into consideration. This equation is then implemented into the commercial finite element software, ABAQUS, via a developed user... 

    Static strain aging behavior of a manganese-silicon steel after single and multi-stage straining

    , Article Journal of Materials Engineering and Performance ; Volume 25, Issue 3 , 2016 , Pages 1047-1055 ; 10599495 (ISSN) Seraj, P ; Serajzadeh, S ; Sharif University of Technology
    Springer New York LLC  2016
    In this work, static strain aging behavior of an alloy steel containing high amounts of silicon and manganese was examined while the influences of initial microstructure and pre-strain on the aging kinetics were evaluated as well. The rate of strain aging in a low carbon steel was also determined and compared with that occurred in the alloy steel. The rates of static strain aging in the steels were defined at room temperature and at 95 °C by means of double-hit tensile testing and hardness measurements. In addition, three-stage aging experiments at 80 °C were carried out to estimate aging behavior under multi-pass deformation processing. The results showed that in-solution manganese and... 

    Energy absorption in plastic expansion of circular metal tubes

    , Article Computational Plasticity X - Fundamentals and Applications, 2 September 2009 through 4 September 2009, Barcelona ; 2009 ; 9788496736696 (ISBN) Azizi, R ; Salehghaffari, S ; Sharif University of Technology
    This paper investigates a new method of dissipating energy in which a rigid tube is driven into the deformable tube under axial compression. Since there is a specific clearance between the rigid and deformable tubes, the deformable tube is expanded during axial compression, and the impact energy is absorbed by plastic expansion of deformable tube and frictional energy between deformable and rigid tubes. Quasi-static axial compression tests with different values of friction coefficient between rigid and deformable tubes are performed. Theoretical formulation with consideration of strain hardening effect is presented to predict the mean crushing load. Theoretical and experimental studies show... 

    An investigation into the effect of strain ageing on mechanical properties of low-carbon steels after warm rolling

    , Article International Journal of Advanced Manufacturing Technology ; Volume 40, Issue 7-8 , 2009 , Pages 721-728 ; 02683768 (ISSN) Serajzadeh, S ; Sharif University of Technology
    In this study, the effect of strain ageing on mechanical properties of warm-rolled steel is investigated. Warm-rolling experiments together with mechanical testing are employed to investigate the effect of processing parameters on the ageing kinetics during and after warm rolling of a low-carbon steel. To do so, the occurrence of dynamic strain ageing is first determined by means of a two-dimensional thermo-mechanical model and then the effect of this phenomenon on the subsequent static strain ageing after warm rolling is studied employing mechanical testing. The results show that the occurrence of dynamic strain ageing during warm rolling may effectively alter the progress of the subsequent...