• Title/Summary/Keyword: Finite element method

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Elastic-plastic Analysis of a 3-Dimensional Inner Crack Using Finite Element Alternating Method (유한요소 교호법을 이용한 삼차원 내부 균열의 탄소성 해석)

  • Park, Jai-Hak;Park, Sang-Yun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.10
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    • pp.1009-1016
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    • 2007
  • Finite element alternating method has been suggested and used effectively to obtain the fracture parameters in assessing the integrity of cracked structures. The method obtains the solution from alternating independently between the FEM solution for an uncracked body and the crack solution in an infinite body. In the paper, the finite element alternating method is extended in order to obtain the elastic-plastic stress fields of a three dimensional inner crack. The three dimensional crack solutions for an infinite body were obtained using symmetric Galerkin boundary element method. As an example of a three dimensional inner crack, a penny-shaped crack in a finite body was analyzed and the obtained elastc-plastic stress fields were compared with the solution obtained from the finite element analysis with fine mesh. It is noted that in the region ahead of the crack front the stress values from FEAM are close to the values from FEM. But large discrepancy between two values is observed near the crack surfaces.

Sensitivity Analysis of the Galerkin Finite Element Method Neutron Diffusion Solver to the Shape of the Elements

  • Hosseini, Seyed Abolfazl
    • Nuclear Engineering and Technology
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    • v.49 no.1
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    • pp.29-42
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    • 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 the corresponding eigenvalue are obtained. The results are then validated against the valid results for IAEA-2D and BIBLIS-2D benchmark problems. To investigate the dependency of the results to the type and number of the elements, and shape function order, a sensitivity analysis of the calculations to the mentioned parameters is performed. It is shown that the triangular elements and second order of the shape function in each element give the best results in comparison to the other states.

A fourth order finite difference method applied to elastodynamics: Finite element and boundary element formulations

  • Souza, L.A.;Carrer, J.A.M.;Martins, C.J.
    • Structural Engineering and Mechanics
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    • v.17 no.6
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    • pp.735-749
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    • 2004
  • This work presents a direct integration scheme, based on a fourth order finite difference approach, for elastodynamics. The proposed scheme was chosen as an alternative for attenuating the errors due to the use of the central difference method, mainly when the time-step length approaches the critical time-step. In addition to eliminating the spurious numerical oscillations, the fourth order finite difference scheme keeps the advantages of the central difference method: reduced computer storage and no requirement of factorisation of the effective stiffness matrix in the step-by-step solution. A study concerning the stability of the fourth order finite difference scheme is presented. The Finite Element Method and the Boundary Element Method are employed to solve elastodynamic problems. In order to verify the accuracy of the proposed scheme, two examples are presented and discussed at the end of this work.

Evaluation of Efficiency Uncertainty for Three-phase Induction Motor using Finite Element Analysis (유한요소 해석을 이용한 3상 유도전동기의 효율 불확도 평가)

  • Lee, Ho-Hyun;Park, Han-Seok;Jun, Hee-Deuk;Woo, Kyung-Il
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.4
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    • pp.163-168
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    • 2017
  • This paper presented an evaluation method for the efficiency uncertainty of a three-phase induction motor using finite element analysis. The motor efficiency in the finite element analysis is calculated by the loss separation method as in the actual test. In the process of evaluating the efficiency uncertainty, the difference between the finite element analysis and the actual test is the method of calculating the type-A / B standard uncertainty of the input quantity to estimate the efficiency and each losses. For the input quantities which can confirm the instantaneous values with respect to time, the type-A standard uncertainty in the finite element analysis is calculated from the RMS values or average values having separate periods in the steady state. And, the type-B standard uncertainty in the finite element analysis is assumed to be zero. Also, this paper compared and analyzed the efficiency uncertainty evaluated by the proposed method and the efficiency uncertainty through the actual test.

A Study of Developing Stamping Die by Using One-Step Form Method in Auto-Body Panel Stamping Process (차체 판넬 스템핑 공정에서 One-step Form 해석방법을 이용한 금형개발에 관한 연구)

  • Hwang Jae Sin;Jung Dong Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2 s.233
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    • pp.350-359
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    • 2005
  • Finite element method is a very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate die model is required. Among finite element method, the static-implicit finite element method is applied effectively to analyze real-size auto-body panel stamping processes, which include the forming stage. This study is about analyzing the stamping process problems by using AutoForm commercial software which used static-implicit method. According to this study, the results of simulation will give engineers good information to access the die design of optimization.

Adaptive Finite Element Analysis of 2-D Plane Problems Using the R-P version (R-P법에 의한 이차원 평면문제의 적응 유한요소 해석)

  • Chung, Sang-Wook;Lim, Jang-Keun
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.345-350
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    • 2000
  • Adaptive finite element analysis, which its solution error meets with the user defined allowable error, is recently used far improving reliability of finite element analysis results. This adaptive analysis is composed of two procedures; one is the error estimation of an analysis result and another is the reconstruction of finite elements. In the rp-method, an element size is controlled by relocating of nodal positions(r-method) and the order of an element shape function is determined by the hierarchical polynomial(p-method) corresponding to the element solution error. In order to show the effectiveness and accuracy of the suggested rp-method, various numerical examples were analyzed and these analysis results were examined by comparing with those obtained by the existed methods. As a result of this study, following conclusions are obtained. (1) rp-method is more accurate and effective than the r- and p-method. (2) The solution convergency of the rp-method is controlled by means of the iterative calculation numbers of the r- and p- method each other.

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Frictional Contact Analysis of the compression-Induced Crack Surfaces using the Finite element Method (유한요소법을 이용한 압축력으로 인한 균열 표면의 마찰접촉 해석)

  • 김방원;이기수
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.517-522
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    • 2000
  • When a body including a crack inside is subjected to the compressive forces, the crack is closed and sliding occurs on the crack surfaces. In this work, a subsurface crack subjected to a static or moving compressive load is analyzed with the finite element method considering friction on the crack surface. The friction on the crack surface is assumed to follow the Coulomb friction law. A numerical method based on the finite element method and iterative method is applied in this work. And the result is compared with the frictional contact of crack by ANSYS using contact 12 element. The numerical results of two methods are compared with the wellknown analytical solutions, and the accuracy of iterative method is checked..

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A Study on the Criterion for Membrane/Shell Mixed Element and Application to the Rigid-Plastic/Elastic-Plastic Finite Element Analysis (박막/쉘 혼합요소의 판별조건과 강소성/탄소성 유한요소해석 적용에 관한 연구)

  • Jung, Dong-Won;Yang, Kyoung-Boo
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2 s.32
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    • pp.1-10
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    • 1999
  • This study is concerned with the application of new criterion for membrane/shell mixed element in the rigid-plastic finite element analysis and elastic-plastic finite element analysis. The membrane/shell mixed element can be selctively adapted to the pure stretching condition by using membrane or a shell element in the bending effect areas. Thus, membrane/shell mixed element requires a efficient criterion for a distinction between membrane and shell element. In the present study introduce the criterion using the angle of between two element and confirm a generality of criterion from appling the theory to a rigid-plastic and elastic-plastic problems.

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Updating Algorithms of Finite Element Model Using Singular Value Decomposition and Eigenanalysis (특이값 분해와 고유치해석을 이용한 유한요소모델의 개선)

  • 김홍준;박영필
    • Journal of KSNVE
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    • v.9 no.1
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    • pp.163-173
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    • 1999
  • Precise and reasonable modelling is necessary and indispensable to the analysis of dynamic characteristics of mechanical structures. Also. the effective prediction of the change of modal properties due to the variation of design parameters is required especially for the application of finite element method to the structural dynamics problems. To meet those necessity and requirement, three model updating algorithms are proposed for finite element methods. Those algorithms are based on sensitivity analysis of the modal data obtained from experimental modal analysis(EMA) and analytical modal analysis(AMA). The adapted sensitivity analysis methods of the algorithms are 1)eigensensitivity(EGNS) method. 2)frequency response function sensitivity(FRFS) method. 3)sensitivity based element-by-element method (SBEEM), Singular value decomposition(SVD) is used for performing eigenanalysis and parameter estimation in the updating process. Those algorithms are applied to finite element of a plate and the updating capability of each algorithm is compared in terms of accuracy. reliability and stability of the updating process. It is shown that the model updating method using frequency response function is superior to the other methods in view of various updating capabilities.

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