Search for: elasticity
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    Two-dimensional porous graphitic carbon nitride C6N7 monolayer: first-principles calculations

    , Article Applied Physics Letters ; Volume 119, Issue 14 , 2021 ; 00036951 (ISSN) Bafekry, A ; Faraji, M ; Fadlallah, M. M ; Abdolhosseini Sarsari, I ; Jappor, H. R ; Fazeli, S ; Ghergherehchi, M ; Sharif University of Technology
    American Institute of Physics Inc  2021
    The fabrication of the C6N7 monolayer [Zhao et al., Sci. Bull. 66, 1764 (2021)] motivated us to discover the optical, structural, mechanical, and electronic properties of the C6N7 monolayer by employing the density functional theory (DFT) method. We find that the shear modulus and Young's modulus of the C6N7 monolayer are smaller than the relevant values of graphene. However, Poisson's ratio is more significant than that of graphene. Applying the PBE (HSE06) functional bandgap of the C6N7 monolayer is 1.2 (1.97) eV, and the electronic dispersion is almost isotropic around the Γ point. C6N7 is more active in the ultraviolet region as compared to the visible light region. This study provides... 

    Small-scale oriented elasticity modeling of functionally graded rotating micro-disks with varying angular velocity in the context of the strain gradient theory

    , Article Acta Mechanica ; Volume 232, Issue 6 , 2021 , Pages 2395-2416 ; 00015970 (ISSN) Bagheri, E ; Asghari, M ; Kargarzadeh, A ; Badiee, M ; Sharif University of Technology
    Springer  2021
    During the varying angular speed timespans of the start or shutdown of rotating machinery, the machinery components may be subjected to intense mechanical loadings which should be taken into account by its fabricator in the designing processes. In the microscale rotating systems, where the angular velocity is typically very high, the importance of this issue is much higher. In this paper, a comprehensive strain-gradient elasticity formulation is presented for functionally graded rotating micro-disks under the effects of varying angular velocity. The gradation of the constituent material along the radial direction can be a helpful option to mitigate the stresses in rotating micro-disks under... 

    Elasticity formulation for motion equations of couple stress based micro-rotating disks with varying speeds

    , Article Mechanics Based Design of Structures and Machines ; Volume 49, Issue 1 , 2021 , Pages 1-19 ; 15397734 (ISSN) Bagheri, E ; Asghari, M ; Sharif University of Technology
    Bellwether Publishing, Ltd  2021
    The elasticity formulation for equations of motion of micro-rotating disks in the presence of angular acceleration as well as the corresponding boundary conditions are developed based on the non-classical continuum theory of couple stress. The system of the boundary value problem is derived on the basis of the variational method. Analytical elasticity solutions to the system of equations are then provided. Based on the elasticity solution, the mechanical responses, including the displacement and stress fields, for varying-speed micro-rotating disks are studied. In a numerical case study, the effect of the couple stresses on the distribution of stress and displacement components are... 

    Effect of seismic wave propagation in massed medium on rate-dependent anisotropic damage growth in concrete gravity dams

    , Article Frontiers of Structural and Civil Engineering ; Volume 15, Issue 2 , 2021 , Pages 346-363 ; 20952430 (ISSN) Daneshyar, A ; Mohammadnezhad, H ; Ghaemian, M ; Sharif University of Technology
    Higher Education Press Limited Company  2021
    Seismic modeling of massive structures requires special caution, as wave propagation effects significantly affect the responses. This becomes more crucial when the path-dependent behavior of the material is considered. The coexistence of these conditions renders numerical earthquake analysis of concrete dams challenging. Herein, a finite element model for a comprehensive nonlinear seismic simulation of concrete gravity dams, including realistic soil-structure interactions, is introduced. A semi-infinite medium is formulated based on the domain reduction method in conjunction with standard viscous boundaries. Accurate representation of radiation damping in a half-space medium and wave... 

    Insights into application of acorn shell powder in drilling fluid as environmentally friendly additive: filtration and rheology

    , Article International Journal of Environmental Science and Technology ; Volume 18, Issue 4 , 2021 , Pages 835-848 ; 17351472 (ISSN) Davoodi, S ; Ramezani Saadat Abadi, A ; Rukavishnikov, V ; Minaev, K ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Conventional additives used in drilling fluid may have detrimental short- and long-term impacts on the surrounding environment. The employment of biodegradable green material in drilling fluid as alternative additives will eliminate these harmful impacts. In this study, acorn shell powder is proposed as a novel biodegradable additive for application in drilling fluid. First, the acorn shell powder was prepared and then characterized in terms of chemical structure, particle size, and morphology. The acorn shell powder, with four different concentrations, was then introduced into a water-based fluid; its functionality in the fluid system was evaluated with respect to rheological and filtration... 

    Development of an aeroelastic model based on system identification using boundary elements method

    , Article Aircraft Engineering and Aerospace Technology ; 2021 ; 17488842 (ISSN) Dehghani Firouz Abadi, R ; Borhan Panah, M. R ; Sharif University of Technology
    Emerald Group Holdings Ltd  2021
    Purpose: The purpose of this paper is to analyze the stability of aeroelastic systems using a novel reduced order aeroelastic model. Design/methodology/approach: The proposed aeroelastic model is a reduced-order model constructed based on the aerodynamic model identification using the generalized aerodynamic force response and the unsteady boundary element method in various excitation frequency values. Due to the low computational cost and acceptable accuracy of the boundary element method, this method is selected to determine the unsteady time response of the aerodynamic model. Regarding the structural model, the elastic mode shapes of the shell are used. Findings: Three case studies are... 

    Bacteria cell hydrophobicity and interfacial properties relationships: A new MEOR approach

    , Article Colloids and Interfaces ; Volume 5, Issue 4 , 2021 ; 25045377 (ISSN) Ganji Azad, E ; Javadi, A ; Jahanbani Veshareh, M ; Ayatollahi, S ; Miller, R ; Sharif University of Technology
    MDPI  2021
    For microbial enhanced oil recovery (MEOR), different mechanisms have been introduced. In some of these papers, the phenomena and mechanisms related to biosurfactants produced by certain microorganisms were discussed, while others studied the direct impacts of the properties of microorganisms on the related mechanisms. However, there are only very few papers dealing with the direct impacts of microorganisms on interfacial properties. In the present work, the interfacial properties of three bacteria MJ02 (Bacillus Subtilis type), MJ03 (Pseudomonas Aeruginosa type), and RAG1 (Acinetobacter Calcoaceticus type) with the hydrophobicity factors 2, 34, and 79% were studied, along with their direct... 

    Frequency characteristics of a viscoelastic graphene nanoplatelet–reinforced composite circular microplate

    , Article JVC/Journal of Vibration and Control ; Volume 27, Issue 1-2 , 2021 , Pages 101-118 ; 10775463 (ISSN) Ghabussi, A ; Habibi, M ; NoormohammadiArani, O ; Shavalipour, A ; Moayedi, H ; Safarpour, H ; Sharif University of Technology
    SAGE Publications Inc  2021
    This is the first research on the frequency analysis of a graphene nanoplatelet composite circular microplate in the framework of a numerical-based generalized differential quadrature method. Stresses and strains are obtained using the higher order shear deformation theory. The microstructure is surrounded by a viscoelastic foundation. Rule of the mixture is used to obtain varying mass density and Poisson’s ratio, whereas the module of elasticity is computed by a modified Halpin–Tsai model. Governing equations and boundary conditions of the graphene nanoplatelet composite circular microplate are obtained by implementing Hamilton’s principle. The results show that outer to inner radius ratio... 

    Stochastic fatigue life prediction of Fiber-Reinforced laminated composites by continuum damage Mechanics-based damage plastic model

    , Article International Journal of Fatigue ; Volume 152 , 2021 ; 01421123 (ISSN) Gholami, P ; Farsi, M. A ; Kouchakzadeh, M. A ; Sharif University of Technology
    Elsevier Ltd  2021
    In this paper, the evolution of elastic–plastic damage in the composite laminates under fatigue conditions is modeled. Continuum damage mechanics (CDM) has been coupled with the bridge micromechanics model to estimate the fatigue damage and life for laminated composite structures. Based on the elastic–plastic bridging model, three damage variables are defined. These variables estimate the fiber, matrix, and fiber/matrix damage response at the ply scale. To model the beginning of plastic deformation, a yield function is utilized, and evolution equations of the damage variables are obtained. Then the developed deformation plastic model is calculated. The model parameters are calibrated by... 

    Healthy and diseasedin vitromodels of vascular systems

    , Article Lab on a Chip ; Volume 21, Issue 4 , 2021 , Pages 641-659 ; 14730197 (ISSN) Hosseini, V ; Mallone, A ; Nasrollahi, F ; Ostrovidov, S ; Nasiri, R ; Mahmoodi, M ; Haghniaz, R ; Baidya, A ; Salek, M. M ; Darabi, M. A ; Orive, G ; Shamloo, A ; Dokmeci, M. R ; Ahadian, S ; Khademhosseini, A ; Sharif University of Technology
    Royal Society of Chemistry  2021
    Irregular hemodynamics affects the progression of various vascular diseases, such atherosclerosis or aneurysms. Despite the extensive hemodynamics studies on animal models, the inter-species differences between humans and animals hamper the translation of such findings. Recent advances in vascular tissue engineering and the suitability ofin vitromodels for interim analysis have increased the use ofin vitrohuman vascular tissue models. Although the effect of flow on endothelial cell (EC) pathophysiology and EC-flow interactions have been vastly studied in two-dimensional systems, they cannot be used to understand the effect of other micro- and macro-environmental parameters associated with... 

    A novel procedure for micromechanical characterization of white matter constituents at various strain rates

    , Article Scientia Iranica ; Volume 27, Issue 2 , 2021 , Pages 784-794 ; 10263098 (ISSN) Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Sharif University of Technology  2021
    Optimal hyperplastic coeficients of the micromechanical constituents of the human brain stem were investigated. An evolutionary optimization algorithm was combined with a Finite Element (FE) model of a Representative Volume Element (RVE) to nd the optimal material properties of axon and Extra Cellular Matrix (ECM). The tension and compression test results of a previously published experiment were used for optimizing the material coeficients, and the shear experiment was used for the validation of the resulting constitutive model. The optimization algorithm was used to search for optimal shear moduli and ber sti ness of axon and ECM by tting the average stress in the axonal direction with the... 

    Effect of axonal fiber architecture on mechanical heterogeneity of the white matter—a statistical micromechanical model

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; 2021 ; 10255842 (ISSN) Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    A diffusion tensor imaging (DTI) -based statistical micromechanical model was developed to study the effect of axonal fiber architecture on the inter- and intra-regional mechanical heterogeneity of the white matter. Three characteristic regions within the white matter, i.e., corpus callosum, brain stem, and corona radiata, were studied considering the previous observations of locations of diffuse axonal injury. The embedded element technique was used to create a fiber-reinforced model, where the fiber was characterized by a Holzapfel hyperelastic material model with variable dispersion of axonal orientations. A relationship between the fractional anisotropy and the dispersion parameter of... 

    Experimental investigation on freeze-thaw durability of polymer concrete

    , Article Frontiers of Structural and Civil Engineering ; Volume 15, Issue 4 , 2021 , Pages 1038-1046 ; 20952430 (ISSN) Jafari, K ; Heidarnezhad, F ; Moammer, O ; Jarrah, M ; Sharif University of Technology
    Higher Education Press Limited Company  2021
    Assessing the durability of concrete is of prime importance to provide an adequate service life and reduce the repairing cost of structures. Freeze-thaw is one such test that indicates the ability of concrete to last a long time without a significant loss in its performance. In this study, the freeze-thaw resistance of polymer concrete containing different polymer contents was explored and compared to various conventional cement concretes. Concretes’ fresh and hardened properties were assessed for their workability, air content, and compressive strength. The mass loss, length change, dynamic modulus of elasticity, and residual compressive strength were determined for all types of concretes... 

    Mesoscopic theoretical modeling and experimental study of rheological behavior of water-based drilling fluid containing associative synthetic polymer, bentonite, and limestone

    , Article Journal of Molecular Liquids ; 2021 ; 01677322 (ISSN) Kariman Moghaddam, A ; Davoodi, S ; Ramazani S.A., A ; Minaev, K.M ; Sharif University of Technology
    Elsevier B.V  2021
    Employing an effective rheological model for the flow of drilling fluid that can accurately predict changing conditions is of significant importance in drilling fluid optimization. Traditional generalized Newtonian models cannot predict the time change condition, viscoelastic behavior, role of each component, or microstructural behaviors within the fluid. Consequently, the present research aims to develop constitutive equations in the framework of generalized bracket formalisms and the extra tensor concept that connect the microscopic and macroscopic properties and can overcome the aforementioned problems of traditional rheological models. The developed model is applicable for drilling fluid... 

    Implementation of visco-pseudo-elastic dampers for vibration reduction of sandwich shells using a large deformation FE technique

    , Article International Journal of Mechanical Sciences ; Volume 207 , 2021 ; 00207403 (ISSN) Khorasani, R ; Hosseini Kordkheili, S. A ; Razov, A ; Resnina, N ; Sharif University of Technology
    Elsevier Ltd  2021
    This study introduces a numerical method for investigating the appropriate arrangement of visco-pseudo-elastic dampers applicable to shell and plate structures under large deformation. These passive dampers are considered as discrete shape memory alloy (SMA) wires and viscoelastic layers. The SMA constitutive model is adopted and developed based on carried out experimental tests (i.e., calorimetry and tensile tests) on Ni-rich Nitinol alloy samples. Pseudoelastic, pseudoplastic, strain recovery and de-twinning phenomena are perceived experimentally. The presented model characterizes pseudoelastic response of shape memory alloys. The current finite element formulation is based on an... 

    Nonlinear stress analysis of shell structures in buckling and snapping problems by exact geometry solid-shell elements through sampling surfaces formulation

    , Article International Journal of Non-Linear Mechanics ; Volume 129 , 2021 ; 00207462 (ISSN) Kulikov, G. M ; Bohlooly, M ; Plotnikova, S. V ; Kouchakzadeh, M. A ; Mirzavand, B ; Sharif University of Technology
    Elsevier Ltd  2021
    In this paper, the nonlinear three-dimensional (3D) stress analysis of shell structures in buckling and snapping problems is presented. The exact geometry or geometrically exact (GeX) hybrid-mixed four-node solid-shell element is developed using a sampling surfaces (SaS) method. The SaS formulation is based on the choice of N SaS parallel to the middle surface to introduce the displacements of these surfaces as basic shell unknowns. The SaS are located at the Chebyshev polynomial nodes (roots of the Chebyshev polynomial of degree N), that is, the outer surfaces are not included into a set of SaS. Such choice of unknowns with the consequent use of Lagrange polynomials of degree N–1 in the... 

    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
    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.... 

    Compressive modulus and deformation mechanisms of 3DG foams: Experimental investigation and multiscale modeling

    , Article Nanotechnology ; Volume 32, Issue 48 , 2021 ; 09574484 (ISSN) Mahdavi, S. M ; Adibnazari, S ; Del Monte, F ; Gutiérrez, M. C ; Sharif University of Technology
    IOP Publishing Ltd  2021
    Due to the wide applications of three-dimensional graphene (3DG) foam in bio-sensors, stretchable electronics, and conductive polymer composites, predicting its mechanical behavior is of paramount importance. In this paper, a novel multiscale finite element model is proposed to predict the compressive modulus of 3DG foams with various densities. It considers the effects of pore size and structure and the thickness of graphene walls on 3DG foams' overall behavior. According to the scanning electron microscope images, a unit cell is selected in the microscale step to represent the incidental arrangement of graphene sheets in 3DG foams. After derivation of equivalent elastic constants of the... 

    Modified Green–Lindsay analysis of an electro-magneto elastic functionally graded medium with temperature dependency of materials

    , Article Mechanics of Time-Dependent Materials ; 2021 ; 13852000 (ISSN) Mirparizi, M ; Razavinasab, S. M ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    This article presents a modified Green–Lindsay (MG-L) thermoelasticity model considering temperature and strain rate. Previously, this model has been developed based on the Green–Lindsay theory of thermoelasticity using strain and temperature rate dependent thermoelastic equations. This study analyzes stress and thermal wave propagation of a functionally graded medium exposed to an electromagnetic field and a thermal shock. All magnetic, elastic, and thermal features of the medium are considered to vary in the longitudinal direction. Additionally, the properties of the material are dependent on the temperature in the form of a cubic function. Using the large displacement formulation and the... 

    Resource allocation in space division multiplexed elastic optical networks secured with quantum key distribution

    , Article IEEE Journal on Selected Areas in Communications ; Volume 39, Issue 9 , 2021 , Pages 2688-2700 ; 07338716 (ISSN) Ehsani Moghaddam, E ; Beyranvand, H ; Salehi, J. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, and flexibility requirements of the upcoming 5th-generation (5G) networks. Furthermore, Multi-Core Fibers (MCFs) and Space Division Multiplexing (SDM) technique can be utilized to overcome the capacity limitation of the conventional Single Mode Fibers (SMFs). On the other hand, Quantum Key Distribution (QKD) is an effective solution to address the security issues in 5G transport networks. In this paper, we investigate the performance of QKD over elastic optical networks with multi-core fibers and address the resource allocation problem for quantum and classical channels of QKD (QChs and CChs) and...