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    Analysis of Photo-Mechanical Response of Light Sensitive Homogeneous Hydrogels

    , M.Sc. Thesis Sharif University of Technology Jafari Khoshnabadi, Mohammad Amin (Author) ; Naghdabadi, Reza (Supervisor)
    Abstract
    Light-sensitive hydrogels are advanced materials with modern applications that have the ability to deform with light radiation at specific frequencies. Numerous studies have been conducted to identify the behavior and deformation of these materials. Most studies have experimentally investigated the light-sensitive behavior of hydrogels. On the other hand, modeling the behavior of light-sensitive hydrogels is very complicated, so that the use of these models is possible only in certain cases. Therefore, in the present study, the existing studies have been reviewed in order to simplify the relationships governing the deformation of light-sensitive hydrogels. In this regard, the deformation... 

    A study on subsequent static aging and mechanical properties of hot-Rolled AA2017

    , Article Journal of Materials Engineering and Performance ; Vol. 23, issue. 8 , 2014 , p. 2894-2904 Khalili, L ; Serajzadeh, S ; Sharif University of Technology
    Abstract
    In this work, the effects of rolling parameters, cooling media, and deformation path on mechanical properties and aging behavior of hot-rolled AA2017 were studied. First, hot-rolling experiments were conducted under different working conditions, and the rolled strips were then aged at room temperature for up to 57 days during which hardness and tensile tests were carried out to record the changes in the mechanical properties of the alloy. Furthermore, due to the importance of static recrystallization on subsequent aging behavior, the rate of recrystallization was also computed. To this end, a mathematical model was developed to predict thermomechanical responses during hot rolling using the... 

    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
    2013
    Abstract
    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,... 

    Modeling and experimental study on friction stir welding of artificially aged AA2017 plates

    , Article Materials and Manufacturing Processes ; Volume 28, Issue 6 , 2013 , Pages 683-688 ; 10426914 (ISSN) Mirjalili, A ; Serajzadeh, S ; Jamshidi Aval, H ; Kokabi, A. H ; Sharif University of Technology
    2013
    Abstract
    Thermo-mechanical responses, developed microstructure, and mechanical properties in friction stir welding (FSW) of artificially aged AA2017 plates were investigated. A finite element analysis was first employed to evaluate hot deformation behavior of the alloy during welding. Also, hardness, yield strength, and microstructure of the welded alloy were examined using the results of the model and experimental testing. It was found that strain and temperature fields during welding are asymmetrically distributed and the maximum temperature locates in advancing side. Furthermore, considerable grain refinement is observed in the stir zone where recrystallized grains in the range of 3 to 8 m are... 

    Nanoparticle enhanced solders for increased solder reliability

    , Article Materials Research Society Symposium Proceedings, 28 November 2011 through 2 December 2011, Boston, MA ; Volume 1424 , 2012 , Pages 115-120 ; 02729172 (ISSN) ; 9781605114019 (ISBN) Mokhtari, O ; Roshanghias, A ; Ashayer, R ; Kotadia, H. R ; Khomamizadeh, F ; Kokabi, A.H ; Clode, M. P ; Miodownik, M ; Mannan, S. H ; Sharif University of Technology
    2012
    Abstract
    Due to environmental concerns traditional eutectic tin-lead solder is gradually being replaced in electronic assemblies by "lead-free" solders. During this transition, nanoparticle technology is also being investigated to see whether improvements in joint reliability for high temperature applications can be made. Nanoparticles can be used to harden the solder via Zener pinning of the grain boundaries and reduce fatigue failure. This paper explores the effects of adding Silica nanoparticles to SnAgCu solder, and how the mechanical properties induced in the solder vary with temperature. It is found that above 100°C the mechanical response and microstructure of the normal and nanoparticle... 

    Effect of pore geometry and loading direction on deformation mechanism of rapid prototyped scaffolds

    , Article Acta Materialia ; Volume 60, Issue 6-7 , 2012 , Pages 2778-2789 ; 13596454 (ISSN) Amirkhani, S ; Bagheri, R ; Zehtab Yazdi, A ; Sharif University of Technology
    2012
    Abstract
    Rapid prototyping is a promising technique for producing tissue engineering scaffolds due to its capacity to generate predetermined forms and structures featuring distinct pore architectures. The objective of this study is to investigate the influences of different pore geometries and their orientation with respect to the compressive loading direction on mechanical responses of scaffolds. Plastic models of scaffolds with cubic and hexagonal unit cells were fabricated by three-dimensional (3-D) printing. An in situ imaging technique was utilized to study the progressive compressive deformation of the scaffold models. In both cubic and hexagonal geometries, organized buckling patterns relevant... 

    Effects of rolling reduction on mechanical properties anisotropy of commercially pure titanium

    , Article Materials and Design ; Volume 34 , 2012 , Pages 268-274 ; 02641275 (ISSN) Nasiri Abarbekoh, H ; Ekrami, A ; Ziaei Moayyed, A. A ; Shohani, M ; Sharif University of Technology
    Abstract
    In the present work tensile and tear properties of commercially pure titanium with different rolling reductions and specimens directions were investigated. The experimental results showed that in low levels of deformation the microstructure refining and mechanical twins have fewer significant effects on the anisotropic behavior of both tear and tensile properties and the crystallographic texture controls the mechanical properties anisotropy. The increase in rolling reduction up to 50% led to the formation of strong-basal texture and resulted in the activation of almost same deformation systems and isotropic mechanical response. However, at high levels of deformation, due to the split... 

    Multi-scale modeling of surface effect via the boundary Cauchy-Born method

    , Article International Journal for Numerical Methods in Engineering ; Volume 85, Issue 7 , August , 2011 , Pages 827-846 ; 00295981 (ISSN) Qomi, M. J. A ; Aghaei, A ; Khoei, A. R ; Sharif University of Technology
    2011
    Abstract
    In this paper, a novel multi-scale approach is developed for modeling of the surface effect in crystalline nano-structures. The technique is based on the Cauchy-Born hypothesis in which the strain energy density of the equivalent continua is calculated by means of inter-atomic potentials. The notion of introducing the surface effect in the finite element method is based on the intrinsic function of quadratures, called as an indicator of material behavior. The information of quadratures is derived by interpolating the data from probable representative atoms in their proximity. The technique is implemented by the definition of reference boundary CB elements, which enable to capture not only... 

    Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing

    , Article Materials and Design ; Volume 31, Issue 9 , October , 2010 , Pages 4076-4082 ; 02641275 (ISSN) Vaseghi, M ; Karimi Taheri, A ; Ig Hong, S ; Seop Kim, H ; Sharif University of Technology
    2010
    Abstract
    In this paper, dynamic ageing characteristics associated with the application of equal channel angular pressing (ECAP) to Al6061 alloy at elevated temperatures was investigated. Followed by ECAP, Vickers microhardness measurement on the cross-sectional planes and microstructural observations were undertaken using transmission electron microscopy. The combination of the ECAP process with dynamic ageing at both 100°C and 150°C resulted in a significant increase in hardness. The grain size was measured as ∼160. nm after four passes. A comparison with the published data on the same alloy processed by ECAP at room temperature and statically aged, suggests several advantages in incorporating... 

    Influence of stacking fault energy and short-range ordering on dynamic recovery and work hardening behavior of copper alloys

    , Article Scripta Materialia ; Volume 62, Issue 9 , May , 2010 , Pages 693-696 ; 13596462 (ISSN) Hamdi, F ; Asgari, S ; Sharif University of Technology
    2010
    Abstract
    True stress vs. true strain responses of Cu-6 wt.% Al and Cu-12 wt.% Mn alloys are presented. While Cu-6 wt.% Al alloy shows the typical mechanical response of low stacking fault energy alloys, the Cu-12 wt.% Mn alloy behaved similarly to medium to high stacking fault energy alloys. These findings clearly show that while short-range ordering triggers slip planarity, it has a minor effect on total dynamic recovery of these copper alloys  

    Optimum groove pressing die design to achieve desirable severely plastic deformed sheets

    , Article Materials and Design ; Volume 31, Issue 1 , 2010 , Pages 94-103 ; 02641275 (ISSN) Kazeminezhad, M ; Hosseini, E ; Sharif University of Technology
    2010
    Abstract
    In this paper, considering the problems of common finite element (FE) codes that consider simple constitutive equations, a developed FE code that considers a new constitutive model is used to simulate the behavior of copper sheets under severe plastic deformation (SPD). The new proposed constitutive model, that considers dislocation densities in cell interiors and cell walls of material as true internal state variables, can investigate all stages of flow stress evolution of material during large plastic deformations and also can explain the effects of strain rate magnitude on the mechanical response of material, during room temperature SPD. The proposed FE analysis is used to investigate the... 

    Parametric study of strain rate effects on nanoparticle-reinforced polymer composites

    , Article Journal of Nanomaterials ; Volume 2016 , 2016 ; 16874110 (ISSN) Soltannia, B ; Haji Gholami, I ; Masajedian, S ; Mertiny, P ; Sameoto, D ; Taheri, F ; Sharif University of Technology
    Hindawi Publishing Corporation  2016
    Abstract
    Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP) components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP components. Therefore, a comprehensive understanding of the response of nanoreinforced polymer composites, subjected to various rates of loading, is of paramount importance for developing reliable structures.... 

    Finite element modeling of thermal and mechanical stresses in work-rolls of warm strip rolling process

    , Article Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture ; Volume 230, Issue 6 , 2016 , Pages 1076-1086 ; 09544054 (ISSN) Koohbor, B ; Sharif University of Technology
    SAGE Publications Ltd 
    Abstract
    An integrated mathematical model was developed to study the thermo-mechanical behavior of strips and work-rolls during warm rolling process of steels. A two-dimensional finite element analysis was first employed to solve for the thermo-mechanical response of the rolled strip under steady-state conditions. The calculated roll pressure and temperature fields were then used to apply proper boundary conditions for solving the governing thermo-mechanical problem for the work-roll. The obtained results indicate that in warm strip rolling of steels, the thermal and mechanical stresses developed within the work-roll are comparable; however, the more significant influence is due to heating and... 

    Welding metallurgy of duplex stainless steel during resistance spot welding

    , Article Welding Journal ; Volume 96, Issue 9 , 2017 , Pages 307s-318s ; 00432296 (ISSN) Arabi, S. H ; Pouranvari, M ; Movahedi, M ; Sharif University of Technology
    Abstract
    This paper investigates the metallurgical and mechanical response of 2304 duplex stainless steel-as an interesting candidate for automotive body-in-white applications-to resistance spot welding. The results showed the high cooling rate associated with the resistance spot welding process suppressed the postsolidification ferrite-austenite transformation leading to improper ferrite-austenite phase balance with a reduced volume fraction of austenite and consequent precipitation of chromium-rich nitrides. The effects of welding current, as the key parameter determining the weld heat input, on the austenite volume fraction and precipitation are discussed. The minimum fusion zone hardness... 

    A numerical approach to study the post-yield softening in cellular solids: role of microstructural ordering and cell size distribution

    , Article Acta Mechanica ; Volume 228, Issue 6 , 2017 , Pages 2005-2016 ; 00015970 (ISSN) Goodarzi Hosseinabadi, H ; Bagheri, R ; Altstadt, V ; Sharif University of Technology
    Springer-Verlag Wien  2017
    Abstract
    Designing meta-materials and cellular solids with biomimetic structures has received increasing attention in the past few years partially due to advances in additive manufacturing techniques that have enabled the fabrication of advanced materials with arbitrarily complex microarchitectures and novel functionalities. To impact on this trend, it is essential to develop our understanding about the role of microstructure on mechanical responses of these structures. Although a large literature exists on the general subject, the role of microstructure on the post-yield instability is not yet adequately documented. This research introduces a numerical approach to study the post-yield instability in... 

    Finite-element modeling of thermal aspects in high speed cold strip rolling

    , Article Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture ; Volume 231, Issue 8 , 2017 , Pages 1350-1362 ; 09544054 (ISSN) Koohbor, B ; Moaven, K ; Sharif University of Technology
    SAGE Publications Ltd  2017
    Abstract
    An integrated model based on finite-element method has been proposed to examine the mechanical and thermal responses of strips and work-rolls in tandem and reverse cold rolling operations. The model has been developed such that the influence of various process parameters, such as lubrication, rolling speed, frictional state and back-up rolls, can be examined. Thermal behaviors of the rolled material and the work-rolls have been analyzed using stream-line upwind Petrov-Galerkin approach, in order to make the model applicable to high-speed rolling processes, as well. The results have been compared to the actual on-line measurements and shown to be of acceptable accuracy. Such modeling approach... 

    Process optimization and kinetics for leaching of cerium, lanthanum and neodymium elements from iron ore waste's apatite by nitric acid

    , Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 27, Issue 2 , 2017 , Pages 420-428 ; 10036326 (ISSN) Ferdowsi, A ; Yoozbashizadeh, H ; Sharif University of Technology
    Nonferrous Metals Society of China  2017
    Abstract
    The leaching of rare earth elements (REEs) including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid... 

    Molecular dynamics study of two dimensional silicon dioxides with in-plane negative poisson's ratio

    , Article Computational Materials Science ; Volume 153 , 2018 , Pages 258-267 ; 09270256 (ISSN) Safaei, S ; Tavakoli, R ; Jafary Zadeh, M ; Sharif University of Technology
    Abstract
    In the present work, the mechanical properties, in particular, the Poisson's ratio of four two-dimensional silica structures, called here α,β,γ and δ are studied by means of molecular dynamics simulations. The α structure has been synthesized experimentally and the others have been reported as the most stable low-energy structures that reveal in-plane negative Poisson's ratio based on the first principles calculations. Among these structures, β-silica exhibits the largest in-plane negative Poisson's ratio which is 2–4 times higher than penta-graphene. Our results illustrate that the classical molecular dynamics simulation reproduces results in agreement with those of the first principles... 

    Interrelation between mechanical response, strain field, and local free volume evolution in glassy polymers: seeking the atomistic origin of post-yield softening

    , Article Express Polymer Letters ; Volume 12, Issue 1 , January , 2018 , Pages 2-12 ; 1788618X (ISSN) Goodarzi Hosseinabadi, H ; Bagheri, R ; Gigl, T ; Hugenschmidt, C ; Raps, D ; Altstadt, V ; Sharif University of Technology
    BME-PT and GTE  2018
    Abstract
    A set of complementary experiments are used for the first time to elucidate the interrelation between the mechanical properties, the strain field, and the free volume evolution during non-homogenous compression of aglassy polymer. Two sets of quenched and annealed polystyrene samples, having different free volume histories, are notched and exposed to compression. The variation of both the strain field and the free volume are measured on a microscopic scale via digital image correlation in case of strain and Doppler broadening spectroscopy of positron annihilation line in case of free volume measurements. Eventually, the interplay between the local evolution of free-volume, the local strain... 

    A time-dependent finite element formulation for thick shape memory polymer beams considering shear effects

    , Article International Journal of Applied Mechanics ; Volume 10, Issue 4 , 2018 ; 17588251 (ISSN) Eskandari, A. H ; Baghani, M ; Sohrabpour, S ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2018
    Abstract
    In this paper, employing a thermomechanical small strain constitutive model for shape memory polymers (SMP), a beam element made of SMPs is presented based on the kinematic assumptions of Timoshenko beam theory. Considering the low stiffness of SMPs, the necessity for developing a Timoshenko beam element becomes more prominent. This is due to the fact that relatively thicker beams are required in the design procedure of smart structures. Furthermore, in the design and optimization process of these structures which involves a large number of simulations, we cannot rely only on the time consuming 3D finite element analyses. In order to properly validate the developed formulations, the numeric...