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    Large deformation analysis of elastic cosserat continua by FEM

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Sharbati, E ; Naghdabadi, R ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Based on the non linear terms appearing in the strain tensor in classical continuum mechanics, two expressions for large strain in the Cosserat continuum are proposed. The generalized form of principal of virtual work together with the constitutive equations for an Isotropic elastic Cosserat continuum are used to derive the finite element formulations for elastic large deformation analysis based on the Cosserat theory. The finite element formulations are then applied to a four-node quadrilateral element with three degrees of freedom at each node including two translational and one rotational degrees of freedom. The tension of a semi-infinite plate with a circular whole in the center is... 

    Nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium

    , Article Composites Science and Technology ; Volume 65, Issue 7-8 , 2005 , Pages 1159-1164 ; 02663538 (ISSN) Behfar, K ; Naghdabadi, R ; Sharif University of Technology
    In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding natural frequencies and the associated modes are determined. The modeling is based on the fact that the elastic moduli of a graphene sheet in two perpendicular orientations are different, so the plate is considered to be anisotropic. The graphene layers stacking at the top of each other bond with carbon-carbon van der Waals forces between two adjacent ones. Also, the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. © 2005 Elsevier Ltd. Al rights reserved  

    Interlaminar hygrothermal stresses in laminated plates

    , Article International Journal of Solids and Structures ; Volume 44, Issue 25-26 , 2007 , Pages 8119-8142 ; 00207683 (ISSN) Bahrami, A ; Nosier, A ; Sharif University of Technology
    Within the elasticity formulation the most general displacement field for hygrothermal problems of long laminated composite plates is presented. The equivalent single-layer theories are then employed to determine the global deformation parameters appearing in the displacement fields of general cross-ply, symmetric, and antisymmetric angle-ply laminates under thermal and hygroscopic loadings. Reddy's layerwise theory is subsequently used to determine the local deformation parameters of various displacement fields. An elasticity solution is also developed in order to validate the efficiency and accuracy of the layerwise theory in predicting the interlaminar normal and shear stress... 

    Solving the Path Planning Problem in 3D Continues Space with Application in Elastic Manipulator

    , M.Sc. Thesis Sharif University of Technology Turani, Amir Abbas (Author) ; Asghari, Mohsen (Supervisor)
    Nowadays, robots are become more common in many important applications, such as academic and industrial issues. One of the most important robots are Multi-Arm manipulators which are used in many application such as moving objects, coloring, automatic welding and etc. Working with this kind of robots needs some vital attentions like planning their moving path. It is Because of the large number of obstacles that they face with in the path. Therefore, not only robots are not allowed to collision with themselves, but also they must not touch the obstacles. In the other words, they need Path planning. Generally, the equations of these robots are nonlinear. Therefore, computers and numerical... 

    Forward and Inverse Problem of Seismic Waves

    , M.Sc. Thesis Sharif University of Technology Mojahedi, Mojtaba (Author) ; Moghadasi, Reza (Supervisor)
    Applying of seismic waves and analysing of its reflections is of effective ways in exploration of the internal structur of the Earth. In this method the Earth is considered as a elastic body that seismic waves are propagated in it. In this thesis the how of creation and propagation of seismic waves is modeld at first and then the inverse problem, exploration of the internal structure of the Earth from observed data, is considered  

    Experimental and Analytical Investigation of Elastic-Plastic Behavior of Glass Fiber Reinforced Polymer Composites

    , M.Sc. Thesis Sharif University of Technology Sajadi, Banafshe (Author) ; Naghdabadi, Reza (Supervisor) ; Asghari, Mohsen (Supervisor)
    In this thesis, we aim to study the elastic-plastic behavior of short fiber reinforced composites experimentally and analytically. The experimental investigation is applied to glass fiber-polypropylene composites (PP/GF). The samples are produced by injection process with maximum temperature of 190C. Fibers are randomly oriented in this procedure of fabrication. The samples are tested in tension, and the mechanical strength is measured by changes in fiber content. The Young's modulus is also investigated in these experiments.Also in this thesis, an analytical model for calculation of Young’s modulus of fiber reinforced composite materials is proposed. In this analysis a displacement field is... 

    Design of Electrical Drive for Steer-by-Wire Systems

    , M.Sc. Thesis Sharif University of Technology Afshang, Hamid (Author) ; Tahami, Farzad (Supervisor)
    Hydraulic steering technology has been used in vehicles for decades. Recently, a trend has been seen towards the use of electronic steer-by-wire systems that provide greater design flexibility by customizing the connection between the steering wheel and the steering mechanism. Steer-by-Wire systems (SbW) offer the potential to enhance steering functionality by enabling features such as automatic lane keeping, park assist, variable steer ratio, and advanced vehicle dynamics control. The lack of a steering intermediate shaft significantly enhances vehicle architectural flexibility. The task of a SbW system is two-fold: turning the steered wheels by tracking the hand wheel (HW) rotation and... 

    Investigating Effects of Interphase on Mechanical Properties of Particulate Metal-Matrix Nanocomposites Using Surface Elasticity

    , M.Sc. Thesis Sharif University of Technology Ebrahimi Estahbanati, Parvin (Author) ; Naghdabadi, Reza (Supervisor)
    Due to ignoring the effect of length scale and neglecting the details at nanosize, classical methods are not sufficiently accurate to determine the properties of nanostructured materials. More reliable results can be obtained, using surface elasticity theory. Lots of analytical, experimental and numerical investigations have been done on the effect of interphase on the mechanical properties of polymer nanocomposites whereas metal matrix nanocomposites are in the first stages of analytical and numerical researches and have attracted so much attention.
    The main objective of this research is to investigate the effects of interphase as well as coating, on the mechanical behavior of metal... 

    Estimation Elasticity of Calorie and Macronutrients with Respect to Income in the Islamic Republic of Iran, 2008-2016

    , M.Sc. Thesis Sharif University of Technology Hosseinpour, Mitra Sadat (Author) ; Vesal, Mohammad (Supervisor)
    Inadequate nutrition is perhaps the most important problem facing the poor. Being hungry lowers productivity and decreases individuals’ income. All of these factors conspire to help the poor stay poor. Raising the income of the poor is one solution for this problem if the elasticity of calorie and macronutrients with respect to income is greater than zero. This study employs both nonparametric and parametric methods to obtain the elasticity of per capita calorie and macronutrients with respect to household per capita expenditure. The case presented is for urban areas of Islamic republic of Iran, 2008-2016. Under each estimation strategy we employ, we find a strongly significant and positive... 

    Polysilicon nano-beam model based on modified couple stress and Eringen's nonlocal elasticity theories

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Vol. 63, issue , 2014 , p. 223-228 Miandoab, E. M ; Pishkenari, H. N ; Yousefi-Koma, A ; Hoorzad, H ; Sharif University of Technology
    In recent years, extensive experiments have shown that classical continuum theory cannot predict the behavior of mechanical microstructures with small size. To accurately design and analyze micro- and nano-electro-mechanical systems, size-dependent continuum theories should be used. These theories model micro- and nano-electro-mechanical systems with higher accuracy because they include size-dependent parameters. In this paper, polysilicon nano-beam is modeled using modified couple stress and Eringen's nonlocal elasticity theories. First, partial differential equations governing the vibration of nano-beams are converted to a one D.O.F. differential equations using Galerkin method, resulting... 

    Analytical Solutions of Actin-Retrograde-Flow in a Circular Stationary Cell: A Mechanical Point of View

    , Article Bulletin of Mathematical Biology ; Vol. 76, issue. 3 , March , 2014 , p. 744-760 ; 00928240 Ghasemi, V., A ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
    The network of actin filaments in the lamellipodium (LP) of stationary and migrating cells flows in a retrograde direction, from the membrane periphery toward the cell nucleus. We have theoretically studied this phenomenon in the circular stationary (fully spread) cells. Adopting a continuum view on the LP actin network, new closed-form solutions are provided for the actin-retrograde-flow (ARF) in a polar coordinate system. Due to discrepancy in the mechanical models of the actin network in the ARF regime, solutions are provided for both assumptions of solid and fluid behavior. Other involved phenomena, including polymerizing machine at the membrane periphery, cytosol drag, adhesion... 

    Free-edge stresses in general cross-ply laminates

    , Article Scientia Iranica ; Vol. 21, issue. 2 , April , 2014 , p. 387-402 Yazdani Sarvestani, H ; Sharif University of Technology
    Within elasticity theory, the reduced form of a displacement field is obtained for general cross-ply composite laminates subjected to a bending moment. The firstorder shear deformation theory of plates and Reddy's layerwise theory are then utilized to determine the global deformation parameters and the local deformation parameters appearing in the displacement fields, respectively. For a special set of boundary conditions an elasticity solution is developed to verify the validity and accuracy of the layerwise theory. Finally, various numerical results are presented within the layerwise theory for edge-effect problems of several cross-ply laminates under the bending moment. The results... 

    The relationship between energy consumption and income inresidential and commercialsectors of Iran using STR

    , Article World Applied Sciences Journal ; Volume 22, Issue 6 , Oct , 2013 , Pages 824-830 ; 18184952 (ISSN) Mollaali Kani, A. H ; Abbaspour, M ; Amiri, H ; Beshkhoor, M ; Talaie Shokri, S ; Sharif University of Technology
    Residential and commercial sectors, share a significant portion of energy consumption in Iran; 37 percent of the total per capita consumption. Therefore, identification of the relation between revenue and energy consumption could be a great assistance to policy makers for clarification of policies employed in energy sector. This paper attempts to explore and analyze the relationship between revenue and energy consumption in residential and commercial sectors for the years 1969 to 2009 in Iran by Smooth Transition Regression Models. Smooth transition regression model is a nonlinear time series model which can be considered as a developed form of Switching Regression Model. The obtained... 

    Interface effects on elastic behavior of an edge dislocation in a core-shell nanowire embedded to an infinite matrix

    , Article International Journal of Solids and Structures ; Volume 50, Issue 7-8 , 2013 , Pages 1177-1186 ; 00207683 (ISSN) Gutkin, M. Y ; Enzevaee, C ; Shodja, H. M ; Sharif University of Technology
    The elastic behavior of an edge dislocation located inside the core of a core-shell nanowire which is embedded in an infinite matrix is studied within the surface/interface elasticity theory. The corresponding boundary value problem is solved exactly by using complex potential functions. An important parameter so-called interface characteristic parameter which has the dimension of length and is a combination of the interface moduli enters the formulations. The stress field of the dislocation, image force acting on the dislocation, and the dislocation strain energy is calculated by considering the interface effect. The introduced characteristic parameter allows the examination of the... 

    Effects of surface elasticity on 3D micromechanical modeling of short fiber nanocomposites

    , Article 2012 3rd International Conference on Manufacturing Science and Technology, ICMST 2012, New Delhi, 18 August 2012 through 19 August 2012 ; Volume 622 , 2013 , Pages 975-979 ; 10226680 (ISSN) ; 9783037855638 (ISBN) Saboori, M. A ; Naghdabadi, R ; Sharif University of Technology
    Recent studies have shown that the surface/interface free energy plays an important role in the effective mechanical properties of solids with nanosized inhomogeneity. In the present study, an analytical model is developed for 3D axisymmetric analysis of short fiber nanocomposites including the fiber end region, subjected to an applied axial load considering surface effects. Closed form expressions are obtained for 3D stress filed in the fiber and matrix. Moreover, performing numerical examples, it is shown that the elastic stress field is size dependent in both the fiber and matrix especially for fiber radii less than 50 nm  

    Size-dependent interaction of an edge dislocation with an elliptical nano-inhomogeneity incorporating interface effects

    , Article International Journal of Solids and Structures ; Volume 49, Issue 5 , March , 2012 , Pages 759-770 ; 00207683 (ISSN) Shodja, H. M ; Ahmadzadeh Bakhshayesh, H ; Gutkin, M. Y
    The elastic behavior of an edge dislocation, which is positioned outside of a nanoscale elliptical inhomogeneity, is studied within the interface elasticity approach incorporating the elastic moduli and surface tension of the interface. The complex potential function method is used. The dislocation stress field and the image force acting on the dislocation are found and analyzed in detail. The difference between the solutions obtained within the classical-elasticity and interface-elasticity approaches is discussed. It is shown that for the stress field, this difference can be significant in those points of the inhomogeneity-matrix interface, where the radius of curvature is smaller and which... 

    Surface/interface effect on the scattered fields of an anti-plane shear wave in an infinite medium by a concentric multi-coated nanofiber/nanotube

    , Article European Journal of Mechanics, A/Solids ; Volume 32 , 2012 , Pages 21-31 ; 09977538 (ISSN) Shodja, H. M ; Pahlevani, L ; Sharif University of Technology
    In this paper, the scattering of anti-plane shear waves in an infinite matrix containing a multi-coated nanofiber/nanotube is studied. Based on the fact that the surface to volume ratio for nano-size objects increases, the usual classical theories which generally neglect the surface/interface effects fail to provide reasonable results. Therefore, to analyze the problem the wave-function expansion method is coupled with the surface/interface elasticity theory. In order to provide some quantitative results through consideration of several examples, the knowledge of the relevant surface and/or interface properties of the corresponding constituent materials are required. For this reason, part of... 

    A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces

    , Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) Ojaghnezhad, F ; Shodja, H. M ; Sharif University of Technology
    Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface... 

    Contribution of nonlocal interactions to DNA elasticity

    , Article Journal of Chemical Physics ; Volume 134, Issue 12 , 2011 ; 00219606 (ISSN) Eslami Mossallam, B ; Ejtehadi, M. R ; Sharif University of Technology
    A nonlocal harmonic elastic rod model is proposed to describe the elastic behavior of short DNA molecules. We show that the nonlocal interactions contribute to effective bending energy of the molecule and affect its apparent persistence length. It is also shown that the anomalous behavior which has been observed in all-atom molecular dynamic simulations [A. K. Mazur, Biophys. J. 134, 4507 (2006)] can be a consequence of both nonlocal interactions between DNA base pairs and the intrinsic curvature of DNA  

    A screw dislocation near a circular nano-inhomogeneity in gradient elasticity

    , Article International Journal of Solids and Structures ; Volume 47, Issue 6 , 2010 , Pages 741-750 ; 00207683 (ISSN) Davoudi, K. M ; Gutkin, M. Yu ; Shodja, H. M ; Sharif University of Technology
    A screw dislocation outside an infinite cylindrical nano-inhomogeneity of circular cross section is considered within the isotropic theory of gradient elasticity. Fields of total displacements, elastic and plastic distortions, elastic strains and stresses are derived and analyzed in detail. In contrast with the case of classical elasticity, the gradient solutions are shown to possess no singularities at the dislocation line. Moreover, all stress components are continuous and smooth at the interface unlike the classical solution. As a result, the image force exerted on the dislocation due to the differences in elastic and gradient constants of the matrix and inhomogeneity, remains finite when...