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    Some basis-free expressions for stresses conjugate to Hill's strains through solving the tensor equation AX + XA = C

    , Article International Journal of Solids and Structures ; Volume 45, Issue 11-12 , 2008 , Pages 3584-3595 ; 00207683 (ISSN) Asghari, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
    2008
    Abstract
    In the present paper, some new and compact basis-free expressions are derived for representing stresses conjugate to the Lagrangean Hill's strain measures. Solving a tensor equation in the form of AX + XA = C, a rather simple general expression is obtained for the conjugate stresses in the case of distinct principal stretches. The result decomposes the conjugate stresses additively into two parts, such that one part is coaxial with the right stretch tensor while another part is orthogonal to it. An expression for the case of double-coalescent principal stretches is also obtained. As an example of the general results, simple expressions are obtained for the stress conjugate to the logarithmic... 

    Effect of EPB tunnelling on surface settlement

    , Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 2 , 2007 , Pages 1003-1012 Sadaghiani, M. H ; Aliari, Y ; Sharif University of Technology
    2007
    Abstract
    Settlement is one of the most important effects of tunnelling. In order to minimize this effect, it is necessary to arrange for circumstances to keep the strain and stress state of undisturbed soil within a tight limit. To achieve this, it is common nowadays to use closed face pressurized shields such as EPB TBMs. In this type of shield, face stability and ground settlement control is maintained by pressurizing the tunnel face with adjustment of cutter head thrust and muck removal discharge. In this paper, numerical modeling of excavation of twin tunnels in Tabriz subway is addressed with respect to the effect of EPB tunnelling in settlement control. Settlement and lining thrust are... 

    Conjugate stresses to two-point deformation tensors

    , Article International Journal of Solids and Structures ; Volume 44, Issue 22-23 , 2007 , Pages 7457-7467 ; 00207683 (ISSN) Asghari, M ; Naghdabadi, R ; Sharif University of Technology
    2007
    Abstract
    In this paper some expressions for stresses conjugate to two-point deformation tensors are derived. These expressions are offered in both the component and basis-free forms. Although, the material time rate of a two-point deformation tensor is not an objective quantity, the stress tensor conjugate to it may be determined. The component-form expressions are obtained by using the notion of conjugacy together with the objectivity of the stress power. The component-form expressions are then extended to a unified basis-free form, using a theorem established for this purpose. The specific results are provided for all different cases of distinct and coalescent principal stretches in a... 

    Stresses conjugate to the Jaumann rate of Eulerian strain measures

    , Article Acta Mechanica ; Volume 190, Issue 1-4 , 2007 , Pages 45-56 ; 00015970 (ISSN) Asghari, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
    2007
    Abstract
    In this paper basis-free expressions are derived for the stresses conjugate to the Jaumann rate of the general Eulerian strain measures. The component-form of the expressions is also presented. The basis-free results are compact and also valid for all different cases of distinct and coalescent principal stretches. As an example, the compact basis-free expressions for the stress conjugate to the Jaumann rate of logarithmic strain lnV are determined. © Springer-Verlag Wien 2007  

    Intrinsic expressions for arbitrary stress tensors conjugate to general strain tensors

    , Article Scientia Iranica ; Volume 14, Issue 5 , 2007 , Pages 486-493 ; 10263098 (ISSN) Sohrabpour, S ; Naghdabadi, R ; Asghari, M ; Sharif University of Technology
    Sharif University of Technology  2007
    Abstract
    In this paper, a unified explicit tensorial relation is sought between two stress tensors conjugate to arbitrary and general Hill strains. The approach used for deriving the tensorial relation is based on the eigenprojection method. The result is, indeed, a generalization of the relations that were derived by Farahani and Naghadabadi [1] in 2003 from a component to intrinsic form. The result is unified in the sense that it is valid for all cases of distinct and coalescent principal stretches. Also, in the case of three dimensional Euclidean inner product space, using the derived unified relation, some expressions for the conjugate stress tensors are presented. © Sharif University of... 

    Unified basis-free relation between two stress tensors conjugate to arbitrary Hill's strain measures

    , Article ASME PVP2006/ICPVT-11 Conference, Vancouver, BC, 23 July 2006 through 27 July 2006 ; Volume 2006 , 2006 ; 0277027X (ISSN); 0791837823 (ISBN); 9780791837825 (ISBN) Asghari, M ; Naghdabadi, R ; Sharif University of Technology
    American Society of Mechanical Engineers(ASME)  2006
    Abstract
    The concept of energy conjugacy for stress and strain measures states that a stress tensor T is conjugate to a strain measure E if T: Ė provides the rate of change of the internal energy per unit reference volume of the body in an adiabatic process. The applications of the conjugate stress and strain measures are in the development of the basic relations in nonlinear analysis of solids. In this paper using eigenprojection method, unified explicit basis-free relation between two arbitrary stress tensors T(f) and T (g), respectively conjugate to two measures of Hill's strains is determined. The result is valid for arbitrary dimension of the Euclidean inner product space and for all cases of... 

    The effects of die geometry in tube channel pressing: Severe plastic deformation

    , Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 230, Issue 1 , 2016 , Pages 263-272 ; 14644207 (ISSN) Farshidi, MH ; Kazeminezhad, M ; Sharif University of Technology
    SAGE Publications Ltd 
    Abstract
    The effects of die geometry on the deformation behavior of aluminum 6061 alloy tube in a novel severe plastic deformation (SPD) process called tube channel pressing (TCP) were studied using the Abaqus 6.10 software. Using the optimized die geometry, 1 to 3 passes of TCP is imposed not only to validate the simulation results, but also to investigate the performance of TCP as a SPD process. The finite element method (FEM) simulation results show that the moderated plastic strain, the lower inhomogeneity in distribution of plastic strain, and the lower risk of fracture during process can be obtained using the proper die geometry. In addition, the imposed strain is a mixture of shear strain and... 

    Effects of viscoelastic supports on the behavior of bridges under moving vehicles

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1751-1769 ; 10263098 (ISSN) Samanipour, K ; Vafai, H ; Sharif University of Technology
    Sharif University of Technology  2017
    Abstract
    One of the most important problems facing structural engineers is the analysis of dynamic behavior of bridges subjected to moving vehicles. In addition, viscoelastic supports under bridges change their dynamic behavior under passing traffic loads. This paper presents how to model a bridge with viscoelastic supports and how the maximum dynamic stress of bridges changes during the passing of moving vehicles. Furthermore, this paper presents an algorithm to solve the governing equation of the bridge with viscoelastic supports as well as the equation of motion of a real European truck with different speeds, simultaneously. Using viscoelastic supports with appropriate characteristics can make a... 

    Feasibility Study of Converting a Turbojet Engine to a Turboshaft

    , M.Sc. Thesis Sharif University of Technology Molaei, Reza (Author) ; Durali, Mohammad (Supervisor) ; Hajilouy Benisi, Ali (Supervisor)
    Abstract
    In gas turbine industry, usually turboshaft engines are designed base on turbojet and turbofan gas generators. Hence, the overall cost of product design and manufacturing will decrease and sales and revenues will increase. It is also common to convert aerial engines with their flight life passed to industrial engines. In the present work, the conversion of an existing turbojet in the gas turbine lab of sharif university of technology to a turboshaft has been investigated. In the first step of project, the experimental data of turbojet performance are considered and the design point of the turboshaft engine will be determined. Then, nominal rotational speed of power turbine and zero to three... 

    Axisymmetric thermo-electro-elastic analysis of a piezoelectric half space

    , Article Mathematics and Mechanics of Solids ; Volume 17, Issue 5 , September , 2012 , Pages 500-515 ; 10812865 (ISSN) Kargarnovin, M. H ; Hashemi, R ; Hashemi, M ; Sadeghi, H ; Sharif University of Technology
    2012
    Abstract
    In this study, an analytical solution is presented for thermo-electro- elastic analysis of piezoelectric semi-infinite bodies. For this purpose, governing equations are derived for a transversely isotropic piezoelectric material under an axisymmetric thermo-electro-mechanical loading condition. A general closed-form analytical solution is presented for the complementary and particular parts of the components of the displacement vector and also for the electric potential function. Then, boundary conditions are imposed and in that case an explicit solution is obtained for piezoelectric semi-infinite bodies. Results show that when a piezoelectric half space is subjected to constant/ramp surface... 

    A simple relation in elastic contact problems

    , Article Tribology International ; Volume 41, Issue 5 , 2008 , Pages 341-347 ; 0301679X (ISSN) Adibnazari, S ; Sharafbafi, F ; Sharif University of Technology
    2008
    Abstract
    In this paper, a new relation is introduced that simplifies the determination of the Muskhelishvili's potential function in plane contact problems. The relation is Φ (z) = 1 / 2 [p (z) - i q (z)], which is correct for all uncoupled contact problems. The new relation is proved in a mathematical way and utilized to obtain the potential function in several contact problems. A complete agreement has been observed between our results and the potential functions that have been obtained from complicated methods in the past. Utilization of the new relation simplifies the solution of contact problems and analytical calculation of the stress and displacement fields, which may lead to the design of... 

    Energy pairs in the micropolar continuum

    , Article International Journal of Solids and Structures ; Volume 44, Issue 14-15 , 2007 , Pages 4810-4818 ; 00207683 (ISSN) Ramezani, S ; Naghdabadi, R ; Sharif University of Technology
    2007
    Abstract
    In this paper, the concept of energy pairs in the micropolar continuum is introduced. A brief review of the micropolar continuum theory is presented for using in the subsequent derivations. A mathematical Lagrangian strain and a wryness tensor for the micropolar continuum are introduced. Using the first law of thermodynamics and for isothermal processes, the power of deformation is obtained and the energy pairs in the Eulerian and Lagrangian descriptions are defined. Also, the micropolar stress and couple stress tensors which are energy pairs to the micropolar Lagrangian strain and wryness measures are determined. © 2006 Elsevier Ltd. All rights reserved  

    Basis-free relations for conjugate strains of eshelby-like stress tensors

    , Article Mechanics of Materials ; Volume 39, Issue 7 , 2007 , Pages 637-642 ; 01676636 (ISSN) Behfar, S. K ; Naghdabadi, R ; Arghavani, J ; Asghari, M ; Sharif University of Technology
    2007
    Abstract
    In this paper, a general class of Eshelby-like or weighted stress tensors based on the right stretch tensor is defined as the product of a general type of Lagrangian stress tensor and a class of stretch measure. In addition, basis free relations for conjugate strains of Eshelby-like stress tensors are investigated, which are based on Hill's definition of energy conjugacy. The equations for strain tensors conjugate to Eshelby-like stress tensors are generally determined, but the case in which the conjugate strains are coaxial with the right stretch tensor is mostly investigated. © 2006 Elsevier Ltd. All rights reserved  

    A micromechanics approach for fatigue of unidirectional fibrous composites

    , Article Iranian Polymer Journal (English Edition) ; Volume 16, Issue 4 , 2007 , Pages 219-232 ; 10261265 (ISSN) Zabihpoor, M ; Adibnazari, S ; Sharif University of Technology
    2007
    Abstract
    The overall mechanical properties of composite materials are dependent on the mechanical response of individual constituents and their interactions while they may be relatively easy to determine. This paper represents a simulation process by which the cyclic stresses and fatigue loadings on its constituents could be predicted for an under fatigue loading lamina. Hence, the unidirectional composites fatigue would be studied through its constituents. The proposed model introduces a new coupled stiffness/strength technique by relating lamina stiffness to the stress field in its constituents. Therefore, the stress field and strength considerations in its constituents could be studied when the... 

    Generalized slab method analysis of radial forging with a general curved shape die

    , 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) Afrasiab, H ; Movahhedy, M. R ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. Among parameters affecting process variables, the die geometry is of fundamental importance and greatly influences variables such as forging load, stress distribution on the dies, metal flow during deformation, and surface finish of the forged product. In this paper a generalized slab method analysis of radial forging process is presented which can handle this process with curved shape dies. Results for dies with various curves are presented and it is shown that the analysis reduces to that of Lahoti and Altan [2] when the die... 

    Computational aspects of the cosserat finite element analysis of localization phenomena

    , Article Computational Materials Science ; Volume 38, Issue 2 , 2006 , Pages 303-315 ; 09270256 (ISSN) Sharbati, E ; Naghdabadi, R ; Sharif University of Technology
    2006
    Abstract
    The computational aspects of the finite element solution procedure based on the Cosserat theory are studied for some elastic-plastic problems, in which the localization occurs. For this purpose, the equations of the Cosserat elasto-plasticity, which include effects of couple stress, micro-rotation and length scale, are presented. The Cosserat finite element formulation is derived and an algorithm for the solution procedure is proposed. For the elastic-plastic problems considered here, the mesh-independency of the Cosserat-based results is quantified and effects of the internal length and Cosserat material parameter a are investigated on the results. Also, the influence of the internal length... 

    Thermal Behavior of Concrete Arch Dams Including Water Level Fluctuations

    , M.Sc. Thesis Sharif University of Technology Rahmani, Eisa (Author) ; Ghaemian, Mohsen (Supervisor)
    Abstract
    One of the major reasons causing cracks in external surfaces of concrete arch dams are thermal loads. Therofore, in order to avoid instabilities due to function of thermal loads in association with hydrostatic and hydrodynamic pressures, a precise evaluation of temperature distribution through dam body is indispensable. In this study, effects of thermal loads mostly on upstream surface of Karun-3 concrete arch dam in Iran were examined using a 3-D finite element method considering water level fluctuations. Also the influence of operatvie boundry conditions in our problem which are water temperature, air temperature and solar radiation was precisely taken into account. Moreover, nonlinear... 

    Stress Analysis & Life Assessment of Alestum Locomotive's Wheels using Analytical Techniques

    , M.Sc. Thesis Sharif University of Technology Shayannejad, Mohammad (Author) ; Adib Nazari, Saeed (Supervisor)
    Abstract
    In this thesis contact problem between wheel and rail has been studied. Also rolling contact fatige (RCF) has been studied in detail. Unlike previous studies that have focused on FEM solution, in this study the problem has been formulated based on analytical methods. Evaluating the loads in wheel-rail contact zone is necessary to find the defects. This thesis presents the evaluation of the stress field inside elastic rolling bodies with an elliptic area of contact. This kind of model can be applied to wheel-rail contact mechanics. The problem has been solved for two main models: with friction and without friction. The results have shown that shear stress reaches the maximum magnitude... 

    Cracked Rotors Modeling for Vibration Analysis and Control

    , Ph.D. Dissertation Sharif University of Technology Ebrahimi, Ali Reza (Author) ; Behzad , Mehdi (Supervisor) ; Meghdari, Ali (Supervisor)
    Abstract
    The main aim of this thesis is to develop a mathematical model for vibration analysis of cracked rotors. This model should be a simple and precise model for prediction of the cracked rotor vibration behavior and suitable for vibration control. In order to create such model, the pure bending of a cracked beam is analyzed at first. This analysis is performed for two different orientations of the crack with respect to the beam and the bending vector. In this section a continuous bending model with continuous model for crack is developed which can predict the full deformation of the cracked beam in bending and can estimate the stress distribution in the beam with good approximation. Comparison... 

    Stress and Frictional Force Analysis of Core Jamming in Sarvak Formation (Bangestan Group)

    , M.Sc. Thesis Sharif University of Technology Soleimaninasab, Alireza (Author) ; Jamshidi, Saeed (Supervisor)
    Abstract
    One of the three fundamental methods in reservoir evaluation is coring, other two methods are logging and well test. Coring is an operation during which, samples from formation rock are taken, and used for laboratory tests and examinations. Although coring presents exact information from reservoir rock, its small scale is the reason of some laboratory errors. This operation is fulfilled with special bits. Coring importance shines where it could give us an idea of reservoir conditions; however cannot be develop it, to all of the reservoir. Coring is used to identify rock properties like porosity, permeability, wettability and fluid properties like fluid density or fluid saturation. Rock...