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    Ab initio DFPT Based Constitutive Modelling of Crystalline Solids within Micromorphic Theory with Application to Nano/Micro-structures

    , Ph.D. Dissertation Sharif University of Technology Moosavian, Hashem (Author) ; Mohammad Shodja, Hossein (Supervisor)
    Abstract
    To account for certain essential features of material such as micro-structure effects and dispersive behaviour and optical branches in dispersion curves, a fundamental departure from classical elasticity to generalized continuum theories is required. Among the generalized continuum mechanics, micromorphic elasticity is capable of capturing these physical phenomena completely. In the mathematical framework of micromorphic elasticity, in addition to the traditional elastic moduli tensors, some additional tensors are introduced in the pertinent governing equations of motion. A precise evaluation of the numerical values of the aforementioned elastic moduli tensors in the realm of the... 

    Calculating Interface Energy, Residual Stresses and Elastic Constants of Non-magnetic FCC Metals

    , M.Sc. Thesis Sharif University of Technology Lotfian, Kimia (Author) ; Mohammadi Shoja, Hossein (Supervisor)
    Abstract
    The investigation of interface residual stress and interface elastic moduli tensors plays a crucial role in enhancing the conventional theory of elasticity. These considerations allow us to account for size effects and eliminate nonphysical singularities near defects. The primary objective of this study is to comprehensively calculate interface energy, residual stress components, and interface elastic moduli tensors for various interfaces between non-magnetic fcc metals using density functional theory (DFT). We achieve this by performing ab initio DFT calculations to determine the interface energies for different coherent interfaces among these metals. Subsequently, these energies are... 

    Finite element analysis of a CFRP reinforced retaining wall

    , Article Geomechanics and Engineering ; Volume 10, Issue 6 , 2016 , Pages 757-774 ; 2005307X (ISSN) Ouria, A ; Toufigh, V ; Desai, C ; Toufigh, V ; Saadatmanesh, H ; Sharif University of Technology
    Techno Press 
    Abstract
    Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to 1000 million m2, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two... 

    Mindlin–Eringen anisotropic micromorphic elasticity and lattice dynamics representation

    , Article Philosophical Magazine ; Volume 100, Issue 2 , 2020 , Pages 157-193 Moosavian, H ; Shodja, H. M ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    To account for certain essential features of material such as dispersive behaviour and optical branches in dispersion curves, a fundamental departure from classical elasticity to polar theories is required. Among the polar theories, micromorphic elasticity of appropriate grades and anisotropy is capable of capturing these physical phenomena completely. In the mathematical framework of micromorphic elasticity, in addition to the traditional elastic constants, some additional constants are introduced in the pertinent governing equations of motion. A precise evaluation of the numerical values of the aforementioned elastic constants in the realm of the experimentations poses serious... 

    On the theoretical and molecular dynamic methods for natural frequencies of multilayer graphene nanosheets incorporating nonlocality and interlayer shear effects

    , Article Mechanics of Advanced Materials and Structures ; Volume 29, Issue 20 , 2022 , Pages 2873-2883 ; 15376494 (ISSN) Nikfar, M ; Taati, E ; Asghari, M ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    In this paper, a multiplate nonlocal shear model and molecular dynamic simulations are presented to investigate the effects of interlayer shear and nonlocality on the natural frequencies of multilayer graphene sheets (MLGSs). From one aspect in the optimal design of such structures, the interaction between graphene layers, which can significantly vary the static and dynamic behavior due to lack of solidity of layers stack, should be considered. On the other hand, it is requied that the nonlocality phenomenon which has an effective role in the mechanical analysis of nanostructures is taken into account. To this aim, the equation of motion along with corresponding boundary conditions is... 

    Design, fabrication, and characterization of novel porous conductive scaffolds for nerve tissue engineering

    , Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 64, Issue 18 , 2015 , Pages 969-977 ; 00914037 (ISSN) Baniasadi, H ; Ahmad Ramazani, S. A ; Mashayekhan, S ; Farani, M. R ; Ghaderinezhad, F ; Dabaghi, M ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    Highly conductive polypyrrole/graphene (PYG) nanocomposite was synthesized with chemical oxidation process via emulsion polymerization and used for the preparation of novel porous conductive gelatin/chitosan-based scaffolds. The effect of PYG loading on various properties of scaffolds was investigated. The obtained results indicated that by introducing PYG into the polymeric matrix, the porosity and swelling capacity decreased while electrical conductivity and Young's modulus demonstrated increasing trend. The in vitro biodegradation test revealed that pure gelatin/chitosan matrix lost 80% of its weight after six weeks in the presence of lysozyme whilst the biodegradation rate was... 

    Development of an accurate finite element model for N-layer MR-laminated beams using a layerwise theory

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Taylor and Francis Inc  2017
    Abstract
    Laminated composite beams incorporated with magneto-rheological fluid are being used in variety of critical applications. An N-layer magneto-rheological-laminated beam based on layerwise theory has been developed to study the dynamic characteristics. For simulation purpose, an MR-laminated beam with five layers is considered in which two layers filled with magneto-rheological and three layers are made of composite materials. The results of simulations are compared with existing layerwise, first-order shear-deformation theory and experimental tests where it shows the accuracy and functionality of the present model. The complex shear modulus of magneto-rheological fluid has been determined... 

    Performance evaluation of a new nanocomposite polymer gel for water shutoff in petroleum reservoirs

    , Article Journal of Dispersion Science and Technology ; 2018 ; 01932691 (ISSN) Asadizadeh, S ; Ayatollahi, S ; ZareNezhad, B ; Sharif University of Technology
    Taylor and Francis Inc  2018
    Abstract
    A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100 °C. It is shown that at a high salinity without using SiO2 nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5 Pa and 9.8 Pa respectively. However by incorporation of SiO2 nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56 Pa and 11.57 Pa respectively, which is quite interesting... 

    Vibration characteristics of laminated composite beams with magnetorheological layer using layerwise theory

    , Article Mechanics of Advanced Materials and Structures ; Volume 25, Issue 3 , 2018 , Pages 202-211 ; 15376494 (ISSN) Naji, J ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Taylor and Francis Inc  2018
    Abstract
    Vibration characteristics of laminated composite beams with magnetorheological (MR) layer are investigated using layerwise theory. In most studies, shear strain across the thickness of MR layer has been considered as a constant value, which does not precisely describe the shear strain. In this study, layerwise theory is employed to develop a finite element formulation to investigate MR-laminated beams. Experimental tests under different magnetic fields are carried out to verify the numerical results. Layerwise numerical results are compared with the experimental results and other theories. An empirical expression for complex shear modulus is presented. The effects of MR layer thickness on... 

    Performance evaluation of a new nanocomposite polymer gel for water shutoff in petroleum reservoirs

    , Article Journal of Dispersion Science and Technology ; Volume 40, Issue 10 , 2019 , Pages 1479-1487 ; 01932691 (ISSN) Asadizadeh, S ; Ayatollahi, S ; ZareNezhad, B ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100 °C. It is shown that at a high salinity without using SiO2 nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5 Pa and 9.8 Pa respectively. However by incorporation of SiO2 nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56 Pa and 11.57 Pa respectively, which is quite interesting... 

    Mechanical properties of graphene oxide: A molecular dynamics study

    , Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 24, Issue 9 , 2016 , Pages 594-603 ; 1536383X (ISSN) Khoei, A. R ; Sarkari Khorrami, M ; Sharif University of Technology
    Taylor and Francis Inc 
    Abstract
    In this paper, the mechanical properties of graphene oxide are obtained using the molecular dynamics analysis, including the ultimate stress, Young modulus, shear modulus and elastic constants, and the results are compared with those of pristine graphene. It is observed that the increase of oxide agents (–O) and (–OH) leads to the increase of C–C bond length at each hexagonal lattice and as a result, alter the mechanical properties of the graphene sheet. It is shown that the elasticity modulus and ultimate tensile strength of graphene oxides (–O) and (–OH) decrease significantly causing the failure behavior of graphene sheet changes from the brittle to ductile. The results of shear loading... 

    Numerical modeling of piles in sandy soils considering stress dependent modulus of elasticity

    , Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; 2015 , Pages 973-977 ; 9781138001480 (ISBN) Ahmadi, M. M ; Abadi, S. M ; Sharif University of Technology
    Taylor and Francis - Balkema  2015
    Abstract
    Pile Foundations are used to transfer loads from superstructures to the underlying competent soil layers. Predicting pile bearing capacity is among the most interesting subjects for geotechnical engineers. In this study, a single pile is modeled in axisymmetric condition. The soil is considered to be a sandy soil. Then, results of the model were verified with a full scale pile load test performed by previous researchers. In order to take into consideration the real behavior of sandy soils, a variation of modulus of elasticity with respect to the changes in the mean effective stress was taken into account. The dependency of soil modulus to the mean effective stress makes the model more... 

    Structure, swelling and mechanical behavior of a cationic full-IPN hydrogel reinforced with modified nanoclay

    , Article Iranian Polymer Journal (English Edition) ; Volume 24, Issue 5 , May , 2015 , Pages 379-388 ; 10261265 (ISSN) Kheirabadi, M ; Bagheri, R ; Kabiri, K ; Sharif University of Technology
    Springer-Verlag London Ltd  2015
    Abstract
    Despite various applications of hydrogels, they have poor gel strength and low resistance against crack propagation which lead to the limitation of their applications. For overcoming this inherent weakness, the current study has focused on the simultaneous utilization of interpenetrating polymer network (IPN) structure and nanocomposite hydrogels. It is known that IPN and nanocomposite gels can improve gel strength. The combination of IPN and nanocomposite structure was developed in hydrogels for improving gel strength. For this purpose, bentonite was successfully modified with a cationic surfactant, (3-methacrylamidopropyl) trimethyl ammonium chloride (MAPTAC), as intercalate, and... 

    A comprehensive mathematical simulation of the composite size-dependent rotary 3D microsystem via two-dimensional generalized differential quadrature method

    , Article Engineering with Computers ; 2021 ; 01770667 (ISSN) Liu, H ; Zhao, Y ; Pishbin, M ; Habibi, M ; Bashir, M. O ; Issakhov, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    In this study, frequency simulation and critical angular velocity of a size-dependent laminated rotary microsystem using modified couple stress theory (MCST) as the higher-order elasticity model is undertaken. The centrifugal and Coriolis impacts due to the spinning are taken into account. The size-dependent thick annular microsystem's computational formulation, non-classical governing equations, and corresponding boundary conditions are obtained by using the higher-order stress tensors and symmetric rotation gradient to the strain energy. By using a single material length scale factor, the most recent non-classical approach captures the size-dependency in the annular laminated microsystem.... 

    Forced and free vibrational analysis of viscoelastic nanotubes conveying fluid subjected to moving load in hygro-thermo-magnetic environments with surface effects

    , Article Archives of Civil and Mechanical Engineering ; Volume 22, Issue 4 , 2022 ; 16449665 (ISSN) Sarparast, H ; Alibeigloo, A ; Borjalilou, V ; Koochakianfard, O ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Abstract
    Forced and free vibrational analyses of viscoelastic nanotubes containing fluid under a moving load in complex environments incorporating surface effects are conducted based on the nonlocal strain gradient theory and the Rayleigh beam model. To model the internal nanoflow, the slip boundary condition is employed. Adopting the Galerkin discretization approach, the reduced-order dynamic model of the system is acquired. Analytical and numerical methods are exploited to determine the dynamic response of the system. The impacts of geometry, scale parameter ratio, Knudsen number, fluid velocity, rotary inertia parameter, viscoelastic parameter, surface residual stress, surface elastic modulus, and... 

    A comprehensive mathematical simulation of the composite size-dependent rotary 3D microsystem via two-dimensional generalized differential quadrature method

    , Article Engineering with Computers ; Volume 38 , 2022 , Pages 4181-4196 ; 01770667 (ISSN) Liu, H ; Zhao, Y ; Pishbin, M ; Habibi, M ; Bashir, M. O ; Issakhov, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Abstract
    In this study, frequency simulation and critical angular velocity of a size-dependent laminated rotary microsystem using modified couple stress theory (MCST) as the higher-order elasticity model is undertaken. The centrifugal and Coriolis impacts due to the spinning are taken into account. The size-dependent thick annular microsystem's computational formulation, non-classical governing equations, and corresponding boundary conditions are obtained by using the higher-order stress tensors and symmetric rotation gradient to the strain energy. By using a single material length scale factor, the most recent non-classical approach captures the size-dependency in the annular laminated microsystem.... 

    Characterizing the effect of fines content on the small strain shear modulus of sand-silt mixtures during hydraulic hysteresis

    , Article 4th International Conference on Transportation Geotechnics, ICTG 2021, 23 May 2021 through 26 May 2021 ; Volume 165 , 2022 , Pages 837-849 ; 23662557 (ISSN); 9783030772338 (ISBN) Jebeli, M ; Mohsen Haeri, S ; Khosravi, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Abstract
    Small strain shear modulus, Gmax, is one of the most important parameters for the characterization of the behavior of earth structures subjected to static or dynamic loading conditions. This research presents an experimental laboratory study on the effect of non-plastic fines content and hydraulic hysteresis on the Gmax of unsaturated sandy soils. In this regard, clean Firoozkuh No. 161 silica sand which is classified as poorly graded sand was mixed with different percentages of non-plastic Firoozkuh silt. A set of bender element tests were carried out using two modified triaxial devices. The modifications on these two apparatus were to add HAV ceramic discs for air–water control of... 

    Discrete kernel functions for fcc crystals within eringen’s nonlocal theory of elasticity

    , Article Journal of Elasticity ; Volume 143, Issue 1 , 2021 ; 03743535 (ISSN) Shodja, H. M ; Shahvaghar Asl, S ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    Abstract
    The dilemma with the deficiencies of the nonlocal kernel functions as the building blocks of the Eringen’s nonlocal theory has been of concern. The aim of the current work is to provide a remedy for the calculation of the components of the nonlocal moduli tensor pertinent to face center cubic (fcc) crystals accounting for their true symmetry group. To this end, three new distinct nonlocal kernel functions which are the discrete atomistic Green’s functions in the stress space are obtained through the nonlocal dispersion relations associated with the longitudinal and shear waves in fcc crystals combined with the corresponding ones calculated via ab initio based on density functional... 

    Fabrication mechanism of nanostructured HA/TNTs biomedical coatings: an improvement in nanomechanical and in vitro biological responses

    , Article Journal of Materials Science: Materials in Medicine ; Volume 27, Issue 10 , 2016 ; 09574530 (ISSN) Ahmadi, S ; Riahi, Z ; Eslami, A ; Sadrnezhaad, S. K ; Sharif University of Technology
    Springer New York LLC  2016
    Abstract
    In this paper, a mechanism for fabrication of nanostructured hydroxyapatite coating on TiO2 nanotubes is presented. Also, the physical, biological, and nanomechanical properties of the anodized Ti6Al4V alloy consisting TiO2 nanotubes, electrodeposited hydroxyapatite, and the hydroxyapatite/TiO2 nanotubes double layer coating on Ti6Al4V alloy implants are compared. Mean cell viability of the samples being 84.63 % for uncoated plate, 91.53 % for electrodeposited hydroxyapatite, and 94.98 % for hydroxyapatite/TiO2 nanotubes coated sample were in the acceptable range. Merely anodized prototype had the highest biocompatibility of 110 % with respect to the control sample. Bonding strength of... 

    Nonlinear mechanics of soft composites: hyperelastic characterization of white matter tissue components

    , Article Biomechanics and Modeling in Mechanobiology ; Volume 19, Issue 3 , 2020 , Pages 1143-1153 Yousefsani, S. A ; Shamloo, A ; Farahmand, F ; Sharif University of Technology
    Springer  2020
    Abstract
    This paper presents a bi-directional closed-form analytical solution, in the framework of nonlinear soft composites mechanics, for top-down hyperelastic characterization of brain white matter tissue components, based on the directional homogenized responses of the tissue in the axial and transverse directions. The white matter is considered as a transversely isotropic neo-Hookean composite made of unidirectional distribution of axonal fibers within the extracellular matrix. First, two homogenization formulations are derived for the homogenized axial and transverse shear moduli of the tissue, based on definition of the strain energy density function. Next, the rule of mixtures and...