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    A mathematical model for prediction of austenite phase transformation

    , Article Materials Letters ; Volume 58, Issue 10 , 2004 , Pages 1597-1601 ; 0167577X (ISSN) Serajzadeh, S ; Sharif University of Technology
    2004
    Abstract
    In this study, a model is developed to predict austenite phase transformation by means of Avrami's model and the finite element method. For doing so, the Avrami-type rate equation is evaluated with the modified Euler's method to handle the kinetics of phase change under non-isothermal conditions. Also, to simultaneously consider the effect of temperature variations on austenite decomposition, heat conduction equation is solved using a two-dimensional finite element approach. To establish the reliability of theoretical results, a comparison is made between simulated and experimental cooling curves for two grades of carbon steel. © 2003 Elsevier B.V. All rights reserved  

    Extended finite element method for three-dimensional large plasticity deformations on arbitrary interfaces

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 197, Issue 9-12 , 2008 , Pages 1100-1114 ; 00457825 (ISSN) Khoei, A. R ; Biabanaki, S. O. R ; Anahid, M ; Sharif University of Technology
    2008
    Abstract
    In this paper, the extended finite element method is presented for large elasto-plastic deformation in 3D solid mechanics problems. The X-FEM computational algorithm is presented in the framework of Lagrangian description in order to model the arbitrary interfaces in large deformations. In X-FEM, the material interface is represented independently of element boundaries and the process is accomplished by partitioning the domain with several tetrahedral sub-elements whose Gauss points are used for integration of the domain of elements. The interface between two bodies is modeled by using the X-FEM technique and applying a modified level set enrichment function. In order to simulate the... 

    A different approach to estimate the process parameters in tube hydroforming

    , Article International Journal of Material Forming ; Volume 8, Issue 3 , July , 2015 , pp 355-366 ; ISSN: 19606206 Hashemi, R ; Shirin, M. B ; Einolghozati, M ; Assempour, A ; Sharif University of Technology
    Abstract
    An enhanced unfolding inverse finite element method (IFEM) has been used together with an extended strain-based forming limit diagram (FLD) to develop a fast approach to predict the feasibility of tube hydroforming process of concept part and determine where the failure or defects can occur. In tube hydroforming, the inverse IFEM has been used for estimating the initial length of tube, axial feeding and fluid pressure. The already developed IFEM algorithm used in this study is based on the total deformation theory of plasticity. Although the nature of tube hydroforming is three-dimensional deformation, in this article a modeling technique has been used to perform the computations in... 

    Numerical and experimental analysis of copper electroforming on an aluminum substrate as a rotating cone electrode cell

    , Article ChemistrySelect ; Volume 4, Issue 40 , 2019 , Pages 11839-11847 ; 23656549 (ISSN) Memannavaz, H ; Pebdeni, H. H ; Liaghat, G ; Rahmati, S ; Najafi, M ; Fazeli, H ; Sharif University of Technology
    Wiley-Blackwell  2019
    Abstract
    In this paper, the advantages of numerical simulation to improve the process of copper electroforming are demonstrated. In this regard, the finite element model of copper electroforming for a rotating cone electrode was first prepared and then, the effect of the key parameters, such as applied current density, solution conductivity, electrode spacing, and anode height, on the uniformity of the thickness was investigated. The model combines tertiary current distribution with Bulter–Volmer electrode kinetics and computational fluid dynamics at the turbulent condition. In order to validate the model, a cone-shaped shell was produced by electroforming method in the laboratory. The obtained... 

    Analysis of concrete shallow funicular shells of rectangular plan

    , Article Curved and Layered Structures ; Volume 6, Issue 1 , 2019 , Pages 229-235 ; 23537396 (ISSN) Sabermahany, H ; Rasouli, E ; Mofid, M ; Sharif University of Technology
    De Gruyter Open Ltd  2019
    Abstract
    Analysis of concrete shallow funicular shells of rectangular plan with simply supported boundary conditions under static loads is performed using the Ritz method. Double Fourier series with the unknown constant coefficients are assumed for the displacement components of the shell and their unknown coefficients are determined such that the potential energy of the shell becomes minimum. The solution is presented in a simple form and is suitable for practical applications. The responses of rectangular-plan concrete shallow funicular shells including deflections, strains, internal forces, internal moments and stresses could be easily determined using the proposed semi-analytical method. The Ritz... 

    Analysis of concrete shallow funicular shells of rectangular plan

    , Article Curved and Layered Structures ; Volume 6, Issue 1 , 2019 , Pages 229-235 ; 23537396 (ISSN) Sabermahany, H ; Rasouli, E ; Mofid, M ; Sharif University of Technology
    De Gruyter Open Ltd  2019
    Abstract
    Analysis of concrete shallow funicular shells of rectangular plan with simply supported boundary conditions under static loads is performed using the Ritz method. Double Fourier series with the unknown constant coefficients are assumed for the displacement components of the shell and their unknown coefficients are determined such that the potential energy of the shell becomes minimum. The solution is presented in a simple form and is suitable for practical applications. The responses of rectangular-plan concrete shallow funicular shells including deflections, strains, internal forces, internal moments and stresses could be easily determined using the proposed semi-analytical method. The Ritz... 

    Failure procedure in epoxy adhesive joining composite plates

    , Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; 2020 Fazel, D ; Kadivar, M. H ; Zohoor, H ; Farid, M ; Hematiyan, M. R ; Sharif University of Technology
    Springer  2020
    Abstract
    In this paper, several numerical simulations are performed to study the failure of epoxy adhesive joining composite plates. Different geometries for the joint and its edge are considered, and the effects of these geometries on the failure load are investigated. Moreover, the joints are subjected to different types of loading in order to determine the failure load. The failure theories of composite materials are implemented into the finite element software ABAQUS, and the failure propagation in the joint is studied. © 2020, Shiraz University  

    Experimental and mathematical analysis of electroformed rotating cone electrode

    , Article Korean Journal of Chemical Engineering ; Volume 37, Issue 4 , April , 2020 , Pages 724-729 ; eISSN: 1975-7220 Heydari, H ; Ahmadipouya, S ; Shoaee Maddah, A ; Rokhforouz, M. R ; Sharif University of Technology
    Springer  2020
    Abstract
    In this study, we present results of a mathematical model in which the governing equations of electroforming process were solved using a robust finite element solver (COMSOL Multiphysics). The effects of different parameters including applied current density, solution electrical conductivity, electrode spacing, and anode height on the copper electroforming process have been investigated. An electroforming experiment using copper electroforming cell was conducted to verify the developed model. The obtained results show that by increasing the applied current density, the electroforming process takes place faster, thereby resulting in a higher thickness of the electroformed layer. In addition,... 

    Extended finite element method in an orthotropic cracked medium

    , Article 8th International Conference on Computational Plasticity: Fundamentals and Applications, COMPLAS VIII, Barcelona, 5 September 2005 through 7 September 2005 ; Issue PART 2 , 2005 , Pages 1110-1113 ; 849599979X (ISBN); 9788495999795 (ISBN) Asadpoure, A ; Mohammadi, S ; Vafai, A ; Sharif University of Technology
    2005

    Residual stresses in radial and indentation forging of tubes

    , Article 2005 SAE World Congress, Detroit, MI, 11 April 2005 through 14 April 2005 ; 2005 ; 01487191 (ISSN) Bihamta, R ; Ameli, A ; Movahhedy, M. R ; Mashregi, A. R ; Sharif University of Technology
    SAE International  2005
    Abstract
    Radial forging and indentation forging processes are two processes used for sizing and/or internal profiling of tubes. In this paper, the two processes are simulated using finite element method and their results are compared with Experimental results. The purpose of this paper is to compare the pattern of residual stresses in both processes. Copyright © 2005 SAE International  

    An investigation on strain inhomogeneity in hot strip rolling process

    , Article Journal of Materials Processing Technology ; Volume 128, Issue 1-3 , 2002 , Pages 88-99 ; 09240136 (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Nejati, M ; Izadi, J ; Fattahi, M ; Sharif University of Technology
    2002
    Abstract
    In this paper the velocity and temperature fields during hot strip rolling are determined using a rigid-viscoplastic finite element method together with a microstructural model for handling dynamic phase transformation during hot deformation. Based on these fields, the strain distributions within the rolled metal at different positions in the deformation zone are estimated. The analysis is capable of considering the effects of metallurgical phase transformations as well as various process parameters such as initial strip temperature, rolling speed, lubrication on the strain inhomogeneity produced during the hot rolling process. To assess the reliability of the theoretical analysis, a... 

    Modeling of Uplift and Impact with Finite Element and Generalized Finite Element Methods

    , M.Sc. Thesis Sharif University of Technology Eslahi, Reza (Author) ; Khoei, Amir Reza (Supervisor)
    Abstract
    One of the most important issues in modeling natural phenomena that always takes into consideration is the problem of contact and collision between objects. Finite element method is known as the most basic and commonly used in numerical modeling techniques to simulate the above phenomenon.This method has specific problems such as dependency of this approach to the domain mesh especially near the contact region. Due to the dynamic and complex nature of impact problems in which drastic changes occur in short duration that often deals with large deformations, one of the perennial concerns, is the weaknesses of methods applied to enforce contact constrains, and so it is essential to use an... 

    Development of an inverse finite element method with an initial guess of linear unfolding

    , Article Finite Elements in Analysis and Design ; Vol. 79, issue , 2014 , p. 1-8 Kankarani Farahani, M ; Bostan Shirin, M ; Assempour, A ; Sharif University of Technology
    Abstract
    An inverse finite element method (IFEM) has been developed for estimation of the blank size and prediction of the strain distribution in sheet metal forming. In the inverse method the nodal coordinates in the final shape are known and their corresponding positions on the initial blank should be determined. The developed method deals with logarithmic large strains of membrane triangular elements, virtual work principle and a new approach for friction modeling. This method leads to a system of nonlinear equations which is highly sensitive to the initial guess. In order to avoid the converging problems, especially in the quasi-vertical walls, an appropriate initial guess is introduced. The... 

    3D neutron diffusion computational code based on GFEM with unstructured tetrahedron elements: A comparative study for linear and quadratic approximations

    , Article Progress in Nuclear Energy ; Volume 92 , 2016 , Pages 119-132 ; 01491970 (ISSN) Hosseini, S. A ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    In the present study, the comparison between the results obtained from the linear and quadratic approximations of the Galerkin Finite Element Method (GFEM) for neutronic reactor core calculation was reported. The sensitivity analysis of the calculated neutron multiplication factor, neutron flux and power distributions in the reactor core vs. the number of the unstructured tetrahedron elements and order of the considered shape function was performed. The cost of the performed calculation using linear and quadratic approximation was compared through the calculation of the FOM. The neutronic core calculation was performed for both rectangular and hexagonal geometries. Both the criticality and... 

    The influence of different configurations on position error of linear variable reluctance resolvers

    , Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 955-960 ; 9781509059638 (ISBN) Daniar, A ; Nasiri Gheidari, Z ; Sharif University of Technology
    Abstract
    In this study a new linear variable reluctance (LVR) resolver is proposed for linear motion control systems. The proposed resolver works based on the sinusoidal variation of air-gap length. Both signal and excitation windings are wound on primary teeth while the secondary has no winding. Two different configurations are examined for the sensor: long, stationary primary with short, moving secondary and long, stationary secondary with short, moving primary. The effect of secondary's number/shape of saliencies and primary's winding configuration on the accuracy of detected position is discussed. 2-D and 3-D time stepping finite element method (FEM) are used for analysis. By comparing the... 

    The influence of winding's pole pairs on position error of linear resolvers

    , Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 949-954 ; 9781509059638 (ISBN) Saneie, H ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Abstract
    Using linear position sensors is necessary in linear motion control systems. In this paper the influence of winding's pole pairs on the accuracy of linear resolver is studied. 2-D and 3-D time stepping finite element method (FEM) is used to calculate the performance characteristics of the resolver. The effect of finite mover's length, transverse edge effect and the end windings length are discussed in detail. Then a prototype of the studied resolver along with its experimental test setup is built. Good correlation between simulation and experimental results verified the simulation process. © 2017 IEEE  

    Effects of physical parameters on the accuracy of axial flux resolvers

    , Article IEEE Transactions on Magnetics ; Volume 53, Issue 4 , 2017 ; 00189464 (ISSN) Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Oraee, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    Axial flux resolvers (AFRs) are used in motion control of electrical machines. In this paper, the effects of physical parameters on the accuracy of detected position are studied. The examined parameters are width of slot opening and slot width, number of poles, number of slots per pole and per phase, and skewing of rotor slots. An analytical model based on the winding function method is proposed for the first time in to estimate the error of position signal. The results of the analytical method are verified with 3-D time stepping finite-element method. Finally, the prototype of the studied AFR is constructed and tested. Good agreement between simulation and experimental results confirms the... 

    Numerical modeling of shear band propagation in porous plastic dilatant materials by XFEM

    , Article Theoretical and Applied Fracture Mechanics ; Volume 95 , 2018 , Pages 164-176 ; 01678442 (ISSN) Mikaeili, E ; Liu, P ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    This paper studies mixed-mode shear band propagation behaviors in porous plastic dilatant materials by the extended finite element method (XFEM). The Drucker-Prager elastoplastic model is combined with the strong discontinuity method to simulate the dilatant shear band. First, the dissipative nature of the localized area with displacement jump is integrated into the constitutive model by introducing a cohesive law. A new contribution lies that the yielding function is modified in the localized region to calculate the cohesive traction within the framework of the XFEM. The shear band propagation direction is determined by the singularity of the acoustic tensor and the corresponding... 

    Two Phase Fluid Flow Modeling in Deforming Porous Media Using XFEM Technique

    , M.Sc. Thesis Sharif University of Technology Farrokhpour, Leila (Author) ; Khoei, Amir Reza (Supervisor)
    Abstract
    Geotechnical problems behavior depends on their interaction with existed fluid phases in their voids. In this research three phase porous media is introduced and it’s governing equations is presented. For solving this set of fully coupled dynamic equations finite element method is applied using elements with displacement and pressure degrees of freedom. Essential drawback of FEM method is in discontinuities modeling. In solid mechanic problems, discontinuity may occur in displacement field, such as crack or contact problems, or in their derivatives, such as multi-material problems. Major soil structures include some internal regions that there are some meshing problems during their FEM... 

    Modeling and Prediction Mechanical Properties Foam Graphene Based on Numerical Method

    , M.Sc. Thesis Sharif University of Technology Riazi, Ardalan (Author) ; Adib Nazari, Saeed (Supervisor)
    Abstract
    Purpose of these investigations is modeling and prediction of foam graphene like linear elastic modules and density of that material. In this modeling with two numerical method molecular dynamics and finite element method is used in that with multiscale method various numerical method match together. At the beginning of the modeling various image of foam graphene in Nano abd meso scale in the case of size and scale survaied till with this checking, scale of the work and varios of modeling was created and with this modeling linear elastic modules and density were estimation