Search for: finite-element-method
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    Application of differential quadrature method to investigate dynamics of a curved beam structure acted upon by a moving concentrated load

    , Article Indian Journal of Science and Technology ; Volume 5, Issue 8 , 2012 , Pages 3085-3089 ; 09746846 (ISSN) Nikkhoo, A ; Kananipour, H ; Chavoshi, H ; Zarfam, R ; Sharif University of Technology
    Application of curved beams in special structures requires a special analysis. In this study, the differential quadrature method (DQM) as a well-known numerical method is utilized in the dynamic analysis of the Euler-Bernoulli curved beam problem with a uniform cross section under a constant moving load. DQ approximation of the required partial derivatives is given by a weighted linear sum of the function values at all grid points. A prismatic semicircular arch with simply supported boundary conditions is assumed. The accuracy of the obtained results is corroborated by employing the Galerkin and finite element methods. Finally, the convergence rate of the DQM and Finite Element Method (FEM)... 

    Investigating stage construction in high concrete arch dams

    , Article Indian Journal of Science and Technology ; Volume 8, Issue 14 , July , 2015 ; 09746846 (ISSN) Pourbakhshian, S ; Ghaemian, M ; Sharif University of Technology
    Indian Society for Education and Environment  2015
    Concrete arch dam is a complex geometric structure and designing such a structure requires experience and high knowledge. One of the important parameters in designing concrete arch dams is the tensile stress in arch concrete material. The static analysis results of high arch dam structure depend on structure analysis model, intensively. Stage construction is needed to be focused in modeling high arch dams. In this study, the necessity of considering stage construction in static analysis of dam structure is focused. Modeling stage construction uses Birth and Death technique of elements. Therefore, six stage construction models are provided including applying dam wall weight outright, two... 

    Finite element modeling of incremental bridge launching and study on behavior of the bridge during construction stages

    , Article International Journal of Civil Engineering ; Volume 13, Issue 1 , 2015 , Pages 112-125 ; 17350522 (ISSN) Shojaei, A ; Tajmir Riahi, H ; Hirmand, M ; Sharif University of Technology
    Iran University of Science and Technology  2015
    Incremental launching is a widespread bridge erection technique which may offer many advantages for bridge designers. Since internal forces of deck vary perpetually during construction stages, simulation and modeling of the bridge behavior, for each step of launching, are tedious and time consuming tasks. The problem becomes much more complicated in construction progression. Considering other load cases such as support settlements or temperature effects makes the problem more intricate. Therefore, modeling of construction stages entails a reliable, simple, economical and fast algorithmic solution. In this paper, a new Finite Element (FE) model for study on static behavior of bridges during... 

    Development of galerkin finite element method three-dimensional computational code for the multigroup neutron diffusion equation with unstructured tetrahedron elements

    , Article Nuclear Engineering and Technology ; Volume 48, Issue 1 , 2016 , Pages 43-54 ; 17385733 (ISSN) Hosseini, S. A ; Sharif University of Technology
    Korean Nuclear Society 
    In the present paper, development of the three-dimensional (3D) computational code based on Galerkin finite element method (GFEM) for solving the multigroup forward/adjoint diffusion equation in both rectangular and hexagonal geometries is reported. Linear approximation of shape functions in the GFEM with unstructured tetrahedron elements is used in the calculation. Both criticality and fixed source calculations may be performed using the developed GFEM-3D computational code. An acceptable level of accuracy at a low computational cost is the main advantage of applying the unstructured tetrahedron elements. The unstructured tetrahedron elements generated with Gambit software are used in the... 

    Effects of the hardened nickel coating on the fatigue behavior of CK45 steel: experimental, finite element method, and artificial neural network modeling

    , Article Iranian Journal of Materials Science and Engineering ; Volume 14, Issue 4 , 2017 , Pages 81-99 ; 17350808 (ISSN) Maleki, E ; Kashyzadeh, K. R ; Sharif University of Technology
    Hardened nickel coating is widely used in many industrial applications and manufacturing processes because of its benefits in improving the corrosion fatigue life. It is clear that increasing the coating thickness provides good protection against corrosion. However, it reduces the fatigue life. Thus, applying a thin layer of coated nickel might give an acceptable corrosion protection with minimum loss of the fatigue life. In the present study, the effects of hardened nickel coating with different thicknesses on the fatigue behavior of CK45 mild steel were experimentally investigated. After conducting the experimental tests, we carried out two different modeling approaches of finite element... 

    Analytical model for sight distance analysis on three-dimensional highway alignments

    , Article Transportation Research Record ; Issue 1523 , 1996 , Pages 1-10 ; 03611981 Hassan, Y ; Easa, S. M ; Abd El Halim, A. O ; Sharif University of Technology
    Existing sight distance models are applicable only to two-dimensional (2-D) separate horizontal and vertical alignments or simple elements of these separate alignments (vertical curve, horizontal curve). A new model is presented for determining the available sight distance on 3-D combined horizontal and vertical alignments. The model is based on the curved parametric elements that have been used in the finite element method. The elements presented are rectangular (4-node, 6-node, and 8-node elements) and triangular. These elements are used to represent various features of the highway surface and sight obstructions, including tangents (grades), horizontal curves, vertical curves, traveled... 

    Sensitivity analysis of the galerkin finite element method neutron diffusion solver to the shape of the elements

    , Article Nuclear Engineering and Technology ; Volume 49, Issue 1 , 2017 , Pages 29-42 ; 17385733 (ISSN) Hosseini, S. A ; Sharif University of Technology
    Korean Nuclear Society  2017
    The purpose of the present study is the presentation of the appropriate element and shape function in the solution of the neutron diffusion equation in two-dimensional (2D) geometries. To this end, the multigroup neutron diffusion equation is solved using the Galerkin finite element method in both rectangular and hexagonal reactor cores. The spatial discretization of the equation is performed using unstructured triangular and quadrilateral finite elements. Calculations are performed using both linear and quadratic approximations of shape function in the Galerkin finite element method, based on which results are compared. Using the power iteration method, the neutron flux distributions with... 

    XFEM, strong discontinuities and second-order work in shear band modeling of saturated porous media

    , Article Acta Geotechnica ; Volume 13, Issue 6 , 2018 , Pages 1249-1264 ; 18611125 (ISSN) Mikaeili, E ; Schrefler, B ; Sharif University of Technology
    We investigate shear band initiation and propagation in fully saturated porous media by means of a combination of strong discontinuities (discontinuities in the displacement field) and XFEM. As a constitutive behavior of the solid phase, a Drucker–Prager model is used within a framework of non-associated plasticity to account for dilation of the sample. Strong discontinuities circumvent the difficulties which appear when trying to model shear band formation in the context of classical nonlinear continuum mechanics and when trying to resolve them with classical numerical methods like the finite element method. XFEM, on the other hand, is well suited to deal with problems where a discontinuity... 

    Calculation of creep and shrinkage in tall concrete buildings using nonlinear staged construction analysis

    , Article Asian Journal of Civil Engineering ; Volume 10, Issue 4 , 2009 , Pages 409-426 ; 15630854 (ISSN) Vafaia, A ; Ghabdian, M ; Estekanchi, H. E ; Desai, C. S ; Sharif University of Technology
    This paper attempts to calculate column shortening and differential shortening between columns and walls in concrete frames using a nonlinear staged construction analysis based on the Dirichlet series and direct integration methods. Prototype frame structures are idealized as two-dimensional and the finite element method (FEM) is used to calculate the creep and shrinkage strains. It is verified with respect to published experimental and analytical results. B3 model and methods such as AAEM, EMM, IDM, and RCM are used for verification purposes. For each frame, effects of creep and shrinkage parameters such as relative humidity percent, rate of construction, shrinkage parameter, and concrete... 

    Simulation of welding residual stresses in resistance spot welding, FE modeling and X-ray verification

    , Article Journal of Materials Processing Technology ; Volume 205, Issue 1-3 , 26 August , 2008 , Pages 60-69 ; 09240136 (ISSN) Ranjbar Nodeh, I ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
    In the present study, an electro-thermo-mechanical model is utilized to predict electrical potential, temperature and residual stress distributions during different stages of resistance spot welding. In order to improve accuracy, material properties including physical, thermal and mechanical properties supposed to be temperature-dependent. The employed model is capable of considering the effects of welding parameters such as heat input and welding time on residual stress distribution. The model results are then compared with the measured residual stresses and good agreement is observed. Predictions show that maximum tensile residual stresses are located at the weld center while they are... 

    An enriched-FEM model for simulation of localization phenomenon in Cosserat continuum theory

    , Article Computational Materials Science ; Volume 44, Issue 2 , December , 2008 , Pages 733-749 ; 09270256 (ISSN) Khoei, A. R ; Karimi, K ; Sharif University of Technology
    The standard finite element models, i.e. the finite element methods that use the classical continuum models, suffer from the excessive mesh dependence when a strain-softening model is used. It cannot converge to a meaningful solution and the governing differential equation loses the ellipticity. This paper presents an enriched finite element algorithm for simulation of localization phenomenon using a higher order continuum model based on the Cosserat continuum theory. The governing equations are regularized by adding the rotational degrees-of-freedom to the conventional degrees-of-freedom and including the internal length parameter in the model. The extended finite element method (X-FEM) is... 

    The effect of 3D and 2D deformations on flattened wires

    , Article Journal of Materials Processing Technology ; Volume 202, Issue 1-3 , 2008 , Pages 553-558 ; 09240136 (ISSN) Kazeminezhad, M ; Karimi Taheri, A ; Sharif University of Technology
    To investigate the effect of 3D and 2D deformations on flattened wires, the effective strain fields of flat rolled and sidepressed wires are predicted using the combined finite and slab element method (FSEM) and two-dimensional finite element method (TDFEM), respectively. The validity of the calculated strain fields are verified using the Vickers microhardness test. Utilizing the calculated strain fields, the strain inhomogeneity of the flat rolled and sidepressed wires are investigated. To assess the effects of height to width ratio and frictional condition on the strain inhomogeneity, an inhomogeneity factor (IF) is defined. The results show that for both the flat rolled and sidepressed... 

    Power transformers internal insulation design improvements using electric field analysis through finite-element methods

    , Article IEEE Transactions on Magnetics ; Volume 44, Issue 2 , 2008 , Pages 273-278 ; 00189464 (ISSN) Khaligh, A ; Vakilian, M ; Sharif University of Technology
    Understanding the potential and electric field distribution in the insulation system of a transformer during transients is vital to its construction. Therefore, we have developed a method for electric field analysis inside a power transformer. The method consists of the following steps. 1) A lumped parameter equivalent model is constructed by dividing transformer windings into several blocks. 2) The electric circuit parameters of this model are calculated. 3) Employing the results of the transformer transient model analysis as boundary conditions, a 2-D asymmetrical electric field finite-element analysis is performed to determine electric fields through the windings. The method has been... 

    Finite element modelling simulation of radial forging of tubes without mandrel

    , Article Materials and Design ; Volume 29, Issue 4 , 2008 , Pages 867-872 ; 02613069 (ISSN) Ghaei, A ; Movahhedy, M. R ; Karimi Taheri, A ; Sharif University of Technology
    Elsevier Ltd  2008
    Radial forging is an open forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, as well as for creating internal profiles for tubes such as rifling the gun barrels. The radial forging of tubes is usually performed over a mandrel to create an internal profile and/or size the internal diameter; but the process can also be used without a mandrel when workpiece geometry does not allow it or the internal surface quality is not critical. In some industrial applications, it may not be possible to use a mandrel inside the tubular workpiece, e.g., due to geometrical limitations of the workpiece. In this study, finite element modelling is applied to model the... 

    Prediction of temperature distribution and required energy in hot forging process by coupling neural networks and finite element analysis

    , Article Materials Letters ; Volume 61, Issue 14-15 , 2007 , Pages 3296-3300 ; 0167577X (ISSN) Serajzadeh, S ; Sharif University of Technology
    In this work, a neural network model is used to calculate flow stress of deforming metal as a function of temperature, strain and strain rate. Then, with the aid of this model and employing a finite element analysis, flow behavior of material and the temperature variations in hot upsetting process are predicted. To examine the model, hot nonisothermal forging of a low carbon steel is performed while force-displacement behavior during hot deformation is recorded. A good agreement is observed between the predicted data and the measured results. © 2006 Elsevier B.V. All rights reserved  

    A parametric study on residual stresses and forging load in cold radial forging process

    , Article International Journal of Advanced Manufacturing Technology ; Volume 33, Issue 1-2 , 2007 , Pages 7-17 ; 02683768 (ISSN) Ameli, A ; Movahhedy, M. R ; Sharif University of Technology
    In this work, a comprehensive study of radial forging process is presented through 2-D axisymmetric and 3-D finite element simulations while considering internal tube profile. The tube used in this investigation has four internal helical grooves along its length. The material is modeled with the elastic-plastic behavior, and sliding-sticking friction model is utilized to model the die-workpiece and mandrel-workpiece contacts. The numerical results in the 2-D case are compared with available experimental data. Residual stresses in the forged product, stress concentration around the grooves, pressure distribution on the hammers and mandrel and maximum forging load are studied. The effects of... 

    Investigation on behaviors of acoustoelastic cavities using a novel reduced finite element–dual reciprocity boundary element formulation

    , Article Engineering Applications of Computational Fluid Mechanics ; Volume 15, Issue 1 , 2021 , Pages 1885-1901 ; 19942060 (ISSN) Liu, W ; Bornassi, S ; Shen, Y ; Ghalandari, M ; Haddadpour, H ; Firouzabadi, R. D ; Band, S. S ; Chau, K. W ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    This paper presents the acoustic and structure characteristics of chambers with elastic/rigid baffles and elastic walls using a novel formulation. The acoustic fluid is assumed to be compressible and inviscid, and the effect of mean flow is neglected. The acoustic field is formulated based on the dual reciprocity boundary element method (DRBEM), and the finite element method (FEM) is used to model the structural dynamics of elastic walls. The reduced-order model (ROM) of the coupled system is derived based on modal analysis of the acoustic field with rigid boundaries and the structure in a vacuum. Numerical examples are presented, and the acoustic modes and frequencies of the chambers are... 

    Power transformers internal insulation design improvements through finite element methods

    , Article IEEE TENCON 2004 - 2004 IEEE Region 10 Conference: Analog and Digital Techniques in Electrical Engineering, Chiang Mai, 21 November 2004 through 24 November 2004 ; Volume C , 2004 , Pages C440-C443 Khaligh, A ; Vakilian, M ; IEEE Region 10 ; Sharif University of Technology
    The knowledge of the potential and field distribution in the insulation system of a transformer, during transient excitation is vital to its construction. This paper deals with insulation design improvements of power transformers using electric field analysis. The calculation methods for electric field analysis inside a power transformer impressed with impulse voltage is presented. Initially, a lumped parameter equivalent model is constructed by dividing transformer windings into several blocks and by computing the electric circuit parameters of this model. Next, the electric field is determined employing the results of the transformer transient model circuit analysis as boundary conditions;... 

    Fluid flow and heat transfer around circular cylinders in the presence and no-presence of porous media

    , Article Journal of Porous Media ; Volume 7, Issue 3 , 2004 , Pages 239-247 ; 1091028X (ISSN) Layeghi, M ; Nouri Borujerdi, A ; Sharif University of Technology
    Steady-state laminar and incompressible fluid flow and forced-convection heat transfer from a circular cylinder and an array of circular cylinders in the presence and no-presence of porous media are investigated. Various mathematical and numerical models are compared and the effects of porous media on heat transfer enhancement are studied. Navier-Stokes equations are used for the analysis of laminar fluid flow and heat transfer. However, the Darcy and extended Darcy-Brinkman models are used for the analysis of fluid flow and heat transfer in porous media. The cylinders are at constant temperature and the analysis is restricted to the low- and intermediate-Peclet-number regimes (Pr = 1, Re ≤... 

    Study of mixed-convection heat transfer from an impinging jet to a solid wall using a finite-element method - Application to cooktop modeling

    , Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 46, Issue 4 , 2004 , Pages 387-397 ; 10407790 (ISSN) Karzar Jeddi, M ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
    The mixed-convection flow from a hot vertical impinging jet on a colder horizontal disc has been studied. The geometry is analogous to a conventional burning gas cooktop. A numerical simulation of the system has been carried out using the finite-element method to study the dependence of fluid flow and heat transfer on the geometric, thermal, and fluid flow parameters. Results show that heat transfer efficiency versus several parameters such as inlet velocity magnitude and flue gas temperature has an optimum value, in which heat transfer efficiency is maximum. With thermal conductivity of the solid wall, velocity angle, and solid wall diameter heat transfer efficiency has increasing behavior....