Search for: finite-element-method--fem
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    A novel approach for microparticle separation based on dielectrophoresis method

    , Article Biomedical Physics and Engineering Express ; Volume 5, Issue 3 , 2019 ; 20571976 (ISSN) Rafiefard, N ; Sasanpour, P ; Fardindoost, S ; Irajizad, A ; Sharif University of Technology
    Institute of Physics Publishing  2019
    A novel approach for particles size separation based on dielectrophoresis (DEP) method is introduced and analyzed both computationally and experimentally. The proposed technique has been utilized for the separation of polystyrene (PS) particles with 8, 6 and 2 μm diameters passing through microchannels with planar electrodes. The performance of the technique has been computationally analyzed using the finite element method (FEM). Considering the structure of the planar electrodes, we propose an approach based on applying an electric potential between one of the global electrodes, and a needle touched the top of the cell suspension. Results of both simulation and experiment show that by... 

    Modelling and analysis of the effect of angular velocity and acceleration on brain strain field in traumatic brain injury

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3 A , 2013 ; 9780791856215 (ISBN) Hoursan, H ; Ahmadian, M. T ; Barari, A ; Beidokhti, H. N ; Sharif University of Technology
    Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the facilities for soft tissue modeling have improved and the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of TBI is still being studied. This study aims to present an optimized model of human head including the brain, skull, and the meninges after a comprehensive study of the previous models.... 

    Determination of strain field and heterogeneity in radial forging of tube using finite element method and microhardness test

    , Article Materials and Design ; Volume 38 , June , 2012 , Pages 147-153 ; 02641275 (ISSN) Sanjari, M ; Saidi, P ; Karimi Taheri, A ; Hossein Zadeh, M ; Sharif University of Technology
    Utilizing the Finite Element Method (FEM), the strain field in the radial forging process of tube is calculated at different process conditions and compared with the experimental results achieved using the microhardness test. The effect of various process parameters such as friction, axial feed, back push and front pull forces and die angles on the strain field are investigated. Using the results of the analysis, it is shown that the deformation inhomogeneity, introduced by an Inhomogeneity Factor (IF), is maximum in the inner zone of tube, while the minimum and the maximum effective strains are appeared at the inner zone of tube and about the core of the tube thickness, respectively. Also,... 

    X-FEM modeling of large plasticity deformation; A convergence study on various blending strategies for weak discontinuities

    , Article European Journal of Computational Mechanics ; Volume 24, Issue 3 , 2015 , Pages 79-106 ; 17797179 (ISSN) Khoei, A. R ; Vahab, M ; Ehsani, H ; Rafieerad, M ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    In the extended finite element method (FEM), the transition elements between the enriched and standard elements, which are generally referred as the blending, or partially enriched elements, are often crucial for a good performance of the local partition of unity enrichments. In these elements, the enrichment function cannot be reproduced exactly due to the lack of a partition of unity, and blending elements produce unwanted terms into the approximation that cannot be compensated by the standard final element part of the approximation. In this paper, some optimal X-FEM-type methods reported in literature are employed to study the performance of blending elements in large plastic deformation... 

    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
    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
    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  

    A variable horizon method for coupling meshfree peridynamics to FEM

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 355 , 2019 , Pages 308-322 ; 00457825 (ISSN) Nikpayam, J ; Kouchakzadeh, M. A ; Sharif University of Technology
    Elsevier B.V  2019
    Peridynamics is a nonlocal reformulation of solid mechanics which can reproduce the solution of classical continuum mechanics as its horizon approaches zero. Taking this idea into consideration, we proposed a new coupling approach between meshfree peridynamics and finite element method. An intermediate variable horizon element called “morakkab” is introduced to transfer force and momentum between peridynamic and FEM regions. In the original peridynamic formulation, artificial ghost forces will arise if the horizon varies with position; The creation of these artifacts is avoided by utilizing a modified peridynamic equation of motion based on the concept of co-family. The accuracy of the... 

    Analysis of different material theories used in a FE model of a lumbar segment motion

    , Article Acta of Bioengineering and Biomechanics ; Volume 15, Issue 2 , 2013 , Pages 33-41 ; 1509409X (ISSN) Gohari, E ; Nikkhoo, M ; Haghpanahi, M ; Parnianpour, M ; Sharif University of Technology
    In this study, a nonlinear poroelastic model of intervertebral disc as an infrastructure was developed. Moreover, a new element was defined consisting a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. Using the new element, three different viscoelastic finite element models were prepared for lumbar motion segment (L4/L5). Prolonged loading (short-term and long-term creep) and cyclic loading were applied to the models and the results were compared with results of in vivo tests. Simplification of the models by using the new element leads to reduction of the runtime of the models in dynamic analyses to few minutes without losing the accuracy in the results  

    Development of two-dimensional, multigroup neutron diffusion computer code based on GFEM with unstructured triangle elements

    , Article Annals of Nuclear Energy ; Volume 51 , 2013 , Pages 213-226 ; 03064549 (ISSN) Hosseini, S. A ; Vosoughi, N ; Sharif University of Technology
    Various methods for solving the forward/adjoint equation in hexagonal and rectangular geometries are known in the literatures. In this paper, the solution of multigroup forward/adjoint equation using Finite Element Method (FEM) for hexagonal and rectangular reactor cores is reported. The spatial discretization of equations is based on Galerkin FEM (GFEM) using unstructured triangle elements. Calculations are performed for both linear and quadratic approximations of the shape function; based on which results are compared. Using power iteration method for the forward and adjoint calculations, the forward and adjoint fluxes with the corresponding eigenvalues are obtained. The results are then... 

    Ultrasonic-assisted grinding of Ti6Al4V alloy

    , Article Procedia CIRP ; Volume 1, Issue 1 , 2012 , Pages 353-358 ; 22128271 (ISSN) Nik, M. G ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
    In conventional grinding of hard to cut materials such as Ti6Al4V alloys, surface burning, redeposition and adhesion of chips to the grinding wheel and workpeice occur visibly unless it is carried out at low speeds and with high volume of cutting fluid. Ultrasonic assisted grinding is an efficient machining process which improves the machinability of hard-to-cut materials by changing the kinematics of the process. In this research, the effect of imposition of ultrasonic vibration on the grinding of Ti6Al4V alloy is studied. Longitudinal vibration at ultrasonic frequency range (20 kHz) is applied on the workpiece and machining forces and surface roughness are compared between conventional... 

    A fem study of the overlapping ratio effect on superplastic formation of metal matrix composites

    , Article 27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010, 19 September 2010 through 24 September 2010, Nice ; Volume 3 , 2010 , Pages 1836-1843 ; 9781617820496 (ISBN) Tehrani, M ; Abedian, A ; Sharif University of Technology
    In aerospace applications structures weight is considered as a major performance parameter. One of the most effective manufacturing methods for weight reduction is superplastic forming. By this technique, not only the weight, but also the stress concentration, the cost, and the manufacturing time are noticeably reduced. Additionally, the components with complicated shapes could be formed in a single manufacturing step. Due to the wide demand for whiskers reinforced metal matrix composites (MMCs) in aerospace industries, many research works have been designed to extend the borders of superplastic forming to MMCs materials. In the present study, a 3-D symmetric micromechanical finite element... 

    Modeling of large deformation - Large sliding contact via the penalty X-FEM technique

    , Article Computational Materials Science ; Volume 48, Issue 3 , May , 2010 , Pages 471-480 ; 09270256 (ISSN) Khoei, A. R ; Taheri Mousavi, S.M ; Sharif University of Technology
    In this paper, an extended finite element method is employed to simulate the presence of discontinuities caused by the contact surface. In X-FEM, the need for mesh adaption to interface is neglected and the process is accomplished by partitioning the domain with some triangular sub-elements whose Gauss points are used for integration of the elements. The modified level set technique and the Heaviside enrichment function are employed to approximate the discontinuous displacement field of elements located on the contact surface. The penalty method is used to impose the contact constraints and establish the non-penetration condition. An efficient numerical algorithm is employed to model the... 

    Analysis of Heat Transfer in Laser Assisted Machining of Slip Cast Fused Silica Ceramics

    , Article 7th CIRP Conference on High Performance Cutting, HPC 2016, 31 May 2016 through 2 June 2016 ; Volume 46 , 2016 , Pages 571-574 ; 22128271 (ISSN) Roostaei, H ; Movahhedy, M. R ; Ihlefeldt S ; Wertheim R ; Hochmuth C ; Putz M ; Sharif University of Technology
    Elsevier  2016
    Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low thermal properties. Laser assisted machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, laser assisted machining of slip cast fused silica (SCFS) ceramics is investigated by presenting a numerical thermal analysis of laser effects on material behaviour. A transient three-dimensional heat transfer analysis for laser assisted turning of SCFS is performed using finite element method. Temperature distributions in SCFS cylindrical specimens are obtained. Experimental results are provided to validate the numerical results  

    Motion type analysis of a piezoelectric-actuated vibratory micro-robot in hybrid stick-slip-jump mode

    , Article Journal of Sound and Vibration ; Volume 436 , 2018 , Pages 81-94 ; 0022460X (ISSN) Jalili, H ; Salarieh, H ; Vossoughi, G ; Sharif University of Technology
    Academic Press  2018
    In this paper, the stick-slip-jump motion of a micro-robot with two perpendicular vibratory actuators is studied. A practical model of this micro-robot is designed and fabricated with two Langevin type piezoelectric actuators, which are driven by harmonic voltages. Depending on the amplitude and frequency of the driving voltages of the micro-robot actuators, as well as their phase difference, the type of the motion dynamics and the states of the contact points in the motion (slipping or jumping) are determined. Considering the conditions of the contact points of the micro-robot, the motion is based on the combination of the friction drive principle (stick-slip) and jumping phenomenon. A... 

    Vibrational analysis of single-walled carbon nanotubes using beam element

    , Article Thin-Walled Structures ; Volume 47, Issue 6-7 , 2009 , Pages 646-652 ; 02638231 (ISSN) Sakhaee Pour, A ; Ahmadian, M. T ; Vafai, A ; Sharif University of Technology
    Vibrational analysis of single-walled carbon nanotubes (SWCNTs) is performed using a finite element method (FEM). To this end, the vibrational behavior of bridge and cantilever SWCNTs with different side lengths and diameters is modeled by three-dimensional elastic beams and point masses. The beam element elastic properties are calculated by considering mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice. The mass of each beam element is assumed as point masses at nodes coinciding with the carbon atoms. Implementing the atomistic simulation approach, the natural frequencies of zigzag and armchair SWCNTs are computed. It is observed that the... 

    Design optimization of a double-stage resolver

    , Article IEEE Transactions on Vehicular Technology ; Volume 68, Issue 6 , 2019 , Pages 5407-5415 ; 00189545 (ISSN) Alemi-Rostami, M ; Alipour Sarabi, R ; Rezazadeh, G ; Nasiri Gheidari, Z ; Oraee, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Accurate position estimation is an integral part of any motion control system. Besides, instantaneous position of poles plays an important role in electronic drive system of modern PM machines. Resolvers, due to their structure, are the most reliable position sensors in harsh environments. However, resolvers are not as accurate as optical encoders in normal conditions. To increase the accuracy of these sensors, various solutions are used, such as optimization in winding arrangement, rotor and stator contour, slot-pole combinations, and improvements in resolver-to-digital converter. In this paper, fractional slot concentrated winding is used in an axial flux resolver. By the aid of winding... 

    The impact of multilayered flux diverters on critical current in HTS transformer windings

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 481-485 ; 9781728115085 (ISBN) Moradnouri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Growing interest in high-temperature superconducting (HTS) power devices is the result of commercial availability of the HTS tapes. One of the most promising applications of the HTS technology is HTS transformer. Flux diverters are used for critical current elevation in HTS transformer windings. In this paper multilayered flux diverter arrangements have been introduced to reduce weight and losses of conventional solid flux diverter arrangement. Horizontal and vertical multilayered arrangements have been investigated and compared with solid arrangement. Two dimensional (2D) finite element method (FEM) simulations have been used for comparison between different arrangements  

    Improved winding proposal for wound rotor resolver using genetic algorithm and winding function approach

    , Article IEEE Transactions on Industrial Electronics ; Volume 66, Issue 2 , 2019 , Pages 1325-1334 ; 02780046 (ISSN) Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Oraee, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Among position sensors, resolvers are superior from reliability point of view. However, obtaining lower output voltage harmonics and simple manufacturing process is a challenge in the design and optimization of resolvers. In this paper, a metaheuristic optimization algorithm is used to minimize total harmonic distortion of the output signals, and consequently the estimated position error in concentrated coil wound field resolvers. Meanwhile, to minimize total coil numbers, manufacturing costs, and complexity of the winding process, modified objective function and constraints are proposed. In this way, a modified winding function method is employed for performance analysis of the axial flux... 

    Development of a three-dimensional magnetic equivalent circuit model for axial flux machines

    , Article IEEE Transactions on Industrial Electronics ; Volume 67, Issue 7 , 2020 , Pages 5758-5767 Alipour-Sarabi, R ; Nasiri Gheidari, Z ; Oraee, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Numerical and analytical methods are two methods to evaluate the performance of electrical machines. This article provides a comparison between numerical and analytical methods. Electrical machine software typically uses numerical methods to solve the electromagnetic equations. On the other hand, analytical methods are faster and more intuitive. A general analytical modeling technique to evaluate the performance of axial flux machines including but not limited to wound rotor resolvers is presented here. The proposed model is based on the actual three-dimensional (3-D) magnetic equivalent circuit (MEC). The accuracy of the proposed model depends on the number of radial layers in the... 

    HTS transformer’s partial discharges raised by floating particles and nitrogen bubbles

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 33, Issue 10 , 6 July , 2020 , Pages 3027-3034 Moradnouri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
    Springer  2020
    Presence of defects, conducting particles, nonconducting particles, and nitrogen gas bubbles in the insulation system of high-temperature superconducting (HTS) transformers, mainly inside the liquid nitrogen as its major insulation, can create local field enhancement and consequently partial discharges which eventually lead to the catastrophic failure of the transformer. In this paper, two-dimensional (2D) axisymmetric finite element method (FEM) modeling via COMSOL Multiphysics software has been utilized for the investigation of the impact of size and shape of conducting particles and nitrogen gas bubbles on partial discharge (PD) activities in liquid nitrogen. Conducting particles of...