• 제목/요약/키워드: FEM Formulation

검색결과 229건 처리시간 0.02초

Iterative coupling of precise integration FEM and TD-BEM for elastodynamic analysis

  • Lei, Weidong;Liu, Chun;Qin, Xiaofei;Chen, Rui
    • Structural Engineering and Mechanics
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    • 제67권4호
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    • pp.317-326
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    • 2018
  • The iterative decomposition coupling formulation of the precise integration finite element method (FEM) and the time domain boundary element method (TD-BEM) is presented for elstodynamic problems. In the formulation, the FEM node and the BEM node are not required to be coincident on the common interface between FEM and BEM sub-domains, therefore, the FEM and BEM are independently discretized. The force and displacement converting matrices are used to transfer data between FEM and BEM nodes on the common interface between the FEM and BEM sub-domains, to renew the nodal variables in the process of the iterations for the un-coincident FEM node and BEM node. The iterative coupling formulation for elastodynamics in current paper is of high modeling accuracy, due to the semi-analytical solution incorporated in the precise integration finite element method. The decomposition coupling formulation for elastodynamics is verified by examples of a cantilever bar under a Heaviside-type force and a harmonic load.

와전류탐상의 3차원 유한요소 정식화에 따른 특성 분석 (Characteristic Analysis of Eddy Current Testing According to the finite Element formulations)

  • 이향범
    • 비파괴검사학회지
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    • 제25권5호
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    • pp.384-390
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    • 2005
  • 3차원 유한요소법을 이용하여 와전류탐상의 수치해석을 수행하기 위하여 도체영역에서 자기벡터포텐셜과 전기스칼라포텐셜을 변수로 사용한다. 3차원 모델링을 하기 때문에 미지수가 많이 늘어나기도 하지만, 사용되는 변수 때문에 미지수가 급속히 증가한다. 이 때문에 전기스칼라포텐셜을 제거한 변형자기벡터포텐셜을 사용하여 미지수를 줄이기도 한다 또한 자기벡터포텐셜의 유일성을 보장하기 위하여 정식화 과정에 인위적으로 게이지조건을 집어넣기도 한다. 본 논문에서는 이러한 정식화 과정들이 와전류탐상에 미치는 영향을 검토하고, 와전류탐상에 적절한 정식화방법을 제시하였다.

Multiscale analysis using a coupled discrete/finite element model

  • Rojek, Jerzy;Onate, Eugenio
    • Interaction and multiscale mechanics
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    • 제1권1호
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    • pp.1-31
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    • 2008
  • The present paper presents multiscale modelling via coupling of the discrete and finite element methods. Theoretical formulation of the discrete element method using spherical or cylindrical particles has been briefly reviewed. Basic equations of the finite element method using the explicit time integration have been given. The micr-macro transition for the discrete element method has been discussed. Theoretical formulations for macroscopic stress and strain tensors have been given. Determination of macroscopic constitutive properties using dimensionless micro-macro relationships has been proposed. The formulation of the multiscale DEM/FEM model employing the DEM and FEM in different subdomains of the same body has been presented. The coupling allows the use of partially overlapping DEM and FEM subdomains. The overlap zone in the two coupling algorithms is introduced in order to provide a smooth transition from one discretization method to the other. Coupling between the DEM and FEM subdomains is provided by additional kinematic constraints imposed by means of either the Lagrange multipliers or penalty function method. The coupled DEM/FEM formulation has been implemented in the authors' own numerical program. Good performance of the numerical algorithms has been demonstrated in a number of examples.

Metal forming analysis using meshfree-enriched finite element method and mortar contact algorithm

  • Hu, Wei;Wu, C.T.
    • Interaction and multiscale mechanics
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    • 제6권2호
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    • pp.237-255
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    • 2013
  • In this paper, a meshfree-enriched finite element method (ME-FEM) is introduced for the large deformation analysis of nonlinear path-dependent problems involving contact. In linear ME-FEM, the element formulation is established by introducing a meshfree convex approximation into the linear triangular element in 2D and linear tetrahedron element in 3D along with an enriched meshfree node. In nonlinear formulation, the area-weighted smoothing scheme for deformation gradient is then developed in conjunction with the meshfree-enriched element interpolation functions to yield a discrete divergence-free property at the integration points, which is essential to enhance the stress calculation in the stage of plastic deformation. A modified variational formulation using the smoothed deformation gradient is developed for path-dependent material analysis. In the industrial metal forming problems, the mortar contact algorithm is implemented in the explicit formulation. Since the meshfree-enriched element shape functions are constructed using the meshfree convex approximation, they pose the desired Kronecker-delta property at the element edge thus requires no special treatments in the enforcement of essential boundary condition as well as the contact conditions. As a result, this approach can be easily incorporated into a conventional displacement-based finite element code. Two elasto-plastic problems are studied and the numerical results indicated that ME-FEM is capable of delivering a volumetric locking-free and pressure oscillation-free solutions for the large deformation problems in metal forming analysis.

딥드로잉 판넬의 단면성형 해석을 위한 유한요소법/기하학힘평형법에 관한 연구 (A Study on the FEM/GEM for Sectional Analysis of Deep Drawing Panels)

  • 김종필;금영덕;이종문
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1993년도 추계학술대회 논문집
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    • pp.212-217
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    • 1993
  • A 2-dimensional FEM/GEM program was developed for analyzing forming processes of an arbitrarily shaped draw-die, in which plane strain condition is assumed and linear line elements are employed. FEM formulation adopted a new algorithm for solving force equilibrium as well as non-penetration condition simultaneously. For the case of numerical divergence at nearly final forming stages and the initial guess in Newton-Raphson iterations, geometric force equilibrium method(GEM) is also introduced. The developed program was tested with the simulation of stamping processes of automotive bonnet inner pannel in order to verify the usefulness and validity of FEM/GEM formulation.

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스탬핑 금형의 성형성 평가를 위한 유한요소/기하학힘평형법 프로그램 개발과 응용 (Development and application of FEM/GEM program for evaluating formability of stamping dies)

  • 김종필;금영탁
    • 한국정밀공학회지
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    • 제13권3호
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    • pp.80-93
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    • 1996
  • A 2-dimensional FEM/GEM program was developed under the plane strain assumption using linear line elements for analyzing stretch/draw forming operations of an arbitrarily shaped draw-die. FEM formulation adopted a new algorithm for solving force equilibrium as well as non-penetration condition simultaneously. Also, a rigid-viscoplastic material model with Hill's normal anisotropic yield condition and rate-sensitive hardening law is assumed, along with the Coulomb friction law in the contact regions. For the case of numerical divergence at nearly final forming stages, geometric force equilibrium method(GEM) is also introduced. The developed program was tested by simulating the forming processes of cylindrical punch/open die, and the drawing processes of automotive oilpan and hood inner panel in order to verify the usefulness and validity of FEM/GEM formulation. The numerical simulation verified the validity and robustness of developed program.

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MBD와 FEM을 이용한 단일윤축 모델의 충돌 후 탈선거동의 해석 (Analysis of Collision-induced Derailments of a Wheel-set Model Using MBD and FEM Simulation)

  • 이준호;구정서
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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    • pp.1868-1873
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    • 2011
  • In this paper, a theoretical formulation of a simplified wheel-set model for collision-induced derailments was evaluated by numerical simulations for the wheel-climb derailment and wheel-lift derailment types. The derailment types were classified into the wheel-climb derailment and the wheel-lift derailment according to the friction force direction of the wheel-flange. The wheel-climb derailment type was classified into Climb-up, Climb/Roll-over, and Roll-over-C, and wheel-lift derailment type was classified into Slip-up, Slip/Roll-over and Roll-over-L. To verify the theoretical equations derived for the wheel-climb derailment and the wheel-lift derailment, dynamic simulations using RecurDyn of Functionbay and Ls-Dyna of LSTC were performed and compared for some examples. The derailment predictions of the suggested theoretical formulation were in good agreement with those of the numerical simulations. The direction of the frictional force between the wheel-flange and the rail can be well predicted using the suggested derailment formulation at a initial derailment.

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임의 조건으로 성형되는 박판의 평면변형률 해석 (Plane Strain Analysis of Thin Sheet Forming with Arbitrary Conditions)

  • 금영탁;이승열
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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    • pp.201-212
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    • 1992
  • The plane strain analysis for simulating the stretch/draw forming operation of arbitrarily-shaped tool profiles and arbitrarily draw-in conditions is introduced. An implicit, incremental, updated Lagrangian formulation is employed, introducing a rigid-viscoplastic constitutive equation. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshe without depending on the explicit spatial derivatives of tool surfaces. The FEM formulation is tested in the sections automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains in the stretched section is obtained, but also the numerical stability of current formulation is verified in the two-side draw-in section.

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임의의 성형조건을 갖는 박판의 평면변형율 해석 (Plane Strain Analysis of Sheet Metal with Arbitrary Forming Conditions)

  • 금영탁;이승열
    • 소성∙가공
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    • 제1권1호
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    • pp.95-103
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    • 1992
  • The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

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HYDROPLANING ANALYSIS BY FEM AND FVM - EFFECT OF TIRE ROLLING AND TIRE PATTERN ON HYDROPLANING

  • Nakajima, Y.;Seta, E.;Kamegawa, T.;Ogawa, H.
    • International Journal of Automotive Technology
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    • 제1권1호
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    • pp.26-34
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    • 2000
  • The new numerical procedure for hydroplaning has been developed by considering the following three important factors; fluid/structure interaction, tire rolling, and practical tread pattern. The tire was analyzed by FEM with Lagrangian formulation and the fluid is analyzed by FVM with Eulerian formulation. Since the tire and the fluid are modeled separately and their coupling is automatically computed by the coupling element, the fluid/structure interaction of the complex geometry such as the tire with the tread pattern can be analyzed practically. We verified the predictability of the hydroplaning simulation in the different parameters such as the water flow, the velocity dependence of hydroplaning, and the effect of the tread pattern on hydroplaning. In order to predict the streamline in the contact patch, the procedure of the global-local analysis was developed. Since the streamline could be predicted by this technology, we could develop the new pattern in a short period based on the principle; "make the stream line smooth".

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