• Title/Summary/Keyword: element ratio

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A Comparative Study on the Displacement Behaviour of Triangular Plate Elements (삼각형 판 요소의 변위 거동에 대한 비교 연구)

  • 이병채;이용주;구본웅
    • Computational Structural Engineering
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    • v.5 no.2
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    • pp.105-118
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    • 1992
  • Static performance was compared for the triangular plate elements through some numerical experiments. Four Kirchhoff elements and six Mindlin elements were selected for the comparison. Numerical tests were executed for the problems of rectangular plates with regular and distorted meshes, rhombic plates, circular plates and cantilever plates. Among the Kirchhoff 9 DOF elements, the discrete Kirchhoff theory element was the best. Element distortion and the aspect ratio were shown to have negligible effects on the displacement behaviour. The Specht's element resulted in better results than the Bergan's but it was sensitive to the aspect ratio. The element based on the hybrid stress method also resulted in good results but it assumed to be less reliable. Among the linear Mindlin elements, the discrete shear triangle was the best in view of reliability, accuracy and convergence. Since the thin plate behaviour of it was as good as the DKT element, it can be used effectively in the finite element code regardless of the thickness. As a quadratic Mindlin element, the MITC7 element resulted in best results in almost all cases considered. The results were at least as good as those of doubly refined meshes of linear elements.

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A Note on the Proper Size of a Finite Element for Analysis of Harbor Resonance Problems (항만부진동 해석을 위한 적정 유한요소 크기에 대한 소고)

  • 정원무;박우선
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.1
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    • pp.86-93
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    • 2002
  • In this study, numerical experiments were performed to decide the proper size off finite element for the analysis of harbor resonance problems. Various sizes of finite elements were considered from 1/3 to 1/60 of wavelength to model a fully opened rectangular harbor. Through the numerical results, the proper number of finite elements per wavelength were revealed to be nine within two percents errors allowed in resonant period and amplification ratio, while twelve within one percent error. It was fecund that error rates of resonant periods decrease linearly, while those of amplification ratio decrease with oscillating form as the size of an element decreases. The error of amplification ratio increases more rapidly than that of resonant period in case of element numbers below nine.

Modal Test and Finite Element Model Update of Aircraft with High Aspect Ratio Wings (고세장비 항공기의 모드 시험 및 동특성 유한요소모델 개선)

  • Kim, Sang-Yong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.5
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    • pp.480-488
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    • 2012
  • The aircrafts with high aspect ratio wings made by a composite material have been developed, which enable high energy efficiency and long-term flight by reducing air resistance and structural weight. However, they have difficulties in securing the aeroelastic stability such as the flutter because of their long and flexible wings. The flutter is unstable self-excited-vibration caused by interaction between the structural dynamics and the aerodynamics. It should be verified analytically prior to first flight test that the flutter does not happen in the range of flight mission. Normally, the finite element model is used for the flutter analysis. So it is important to construct the finite element model representing dynamic characteristics similar to those of a real aircraft. Accordingly, in this research, to acquire dynamic characteristics experimentally the modal test of the aircraft with high aspect ratio composite wings was conducted. And then the modal parameters from the finite element analysis(FEA) were compared with those from the modal test. To make analysis results closer to test results, the finite element model was updated by means of the sensitivity analysis on variables and the optimization. Finally, it was proved that the updated finite element model is reliable as compared with the results of the modal test.

Crack Damages in Exterior Wall Structures of Korean High-Rise Apartment Buildings Based on Nonlinear Finite Element Analysis (비선형 유한요소해석 기반 국내 고층아파트 외벽구조의 균열손상 특성 분석)

  • Kim, Sung Hyun;Mo, Sang Yeong;Kim, Si Hyun;Choi, Kyoung Kyu;Kang, Su Min
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.1
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    • pp.47-57
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    • 2024
  • Recently, in newly constructed apartment buildings, the exterior wall structures have been characterized by thinness, having various openings, and a significantly low reinforcement ratio. In this study, a nonlinear finite element analysis was performed to investigate the crack damage characteristics of the exterior wall structure. The limited analysis models for a 10-story exterior wall were constructed based on the prototype apartment building, and nonlinear static analysis (push-over analysis) was performed. Based on the finite element (FE) analysis model, the parametric study was conducted to investigate the effects of various design parameters on the strength and crack width of the exterior walls. As the parameters, the vertical reinforcement ratio and horizontal reinforcement ratio of the wall, as well as the uniformly distributed longitudinal reinforcement ratio and shear reinforcement ratio of the connection beam, were addressed. The analysis results showed that the strength and deformation capacity of the prototype exterior walls were limited by the failure of the connection beam prior to the flexural yielding of the walls. Thus, the increase of wall reinforcement limitedly affected the failure modes, peak strengths, and crack damages. On the other hand, when the reinforcement ratio of the connection beams was increased, the peak strength was increased due to the increase in the load-carrying capacity of the connection beams. Further, the crack damage index decreased as the reinforcement ratio of the connection beam increased. In particular, it was more effective to increase the uniformly distributed longitudinal reinforcement ratio in the connection beams to decrease the crack damage of the coupling beams, regardless of the type of the prototype exterior walls.

Multi-stage Analysis of Elliptic Cup Drawing Processes with the Large Aspect Ratio by an Explicit Elasto-Plastic Finite Element Method (외연적 유한요소법을 이용한 세장비가 큰 타원형 컵 성형공정의 다단계 해석)

  • Kim, S.H.;Kim, S.H.;Huh, H.
    • Transactions of Materials Processing
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    • v.9 no.3
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    • pp.313-319
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    • 2000
  • Finite element analysis is carried out for simulation of the multi-stage elliptic cup drawing process with the large aspect ratio. The analysis incorporates with shell elements for an elasto-plastic finite element method with the explicit time integration scheme. For the simulation, LS-DYNA3D is utilized for its wide capability of solving forming problems. The simulation result shows that the non-uniform drawing ratio at the elliptic cross section ad the small shoulder radius cause failure such as tearing and wrinkling. The result suggests the guideline to modify the tool shape for prevention of the failure during the drawing process.

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Determination of Initial Billet using The Artificial Neural Networks and The Finite Element Method for The Forged Products (신경망과 유한요소법을 이용한 단조품의 초기 소재 결정)

  • 김동진;고대철;김병민;강범수;최재찬
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1994.10a
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    • pp.133-140
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    • 1994
  • In this paper, we have proposed a new method to determine the initial billet for the forged products using a function approximation in neural networks. the architecture of neural network is a three-layer neural network and the back propagation algorithm is employed to train the network. By utilizing the ability of function approximation of neural network, an optimal billet is determined by applying nonlinear mathematical relationship between shape ratio in the initial billet and the final products. A volume of incomplete filling in the die is measured by the rigid-plastic finite element method. The neural network is trained with the initial billet shape ratio and that of the un-filled volume. After learning, the system is able to predict the filling region which are exactly the same or slightly different to results of finite element method. It is found that the prediction of the filling shape ratio region can be made successfully and the finite element method results are represented better by the neural network.

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Vibration Analysis of Tapered Thick Plate Subjected to Static In-plane Stress on Pasternak Foundation (Pasternak지반 위에 놓인 면내력을 받는 변단면 후판의 진동해석)

  • Cheong, Jin-Taek;Lee, Yong-Soo;Oh, Soog-Kyoung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.4 s.97
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    • pp.388-394
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    • 2005
  • This paper has the object of investigating natural frequencies of tapered thick plate on Pasternak foundation by means of finite element method and providing kinetic design data for mat of building structures. Vibration analysis for tapered thick plate subjected to in-plane stress is presented in this paper. Finite element analysis of rectangular plate is done by use of rectangular finite element with 8-nodes. Analysis conditions of tapered thick plate are as follows each. The ratio of in-plane stress to critical load is varied with $0.2\sigma_{cr}$, $0.4\sigma_{cr}$, $0.6\sigma_{cr}$. The Winkler parameter is 0, 10, 100, 1000, the shear foundation parameter is 0, 10 and the taper ratio is 0.0, 0.2, 0.4, 0.6, 0.8.

Dynamic Stability Analysis of Stiffened Tapered Thick Plate with Concentrated Mass on Pasternak Foundations (Pasternak지반에 지지된 집중질량을 갖는 보강된 변단면 후판의 동적안정해석)

  • Lee, Yong-Soo;Kim, Il-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.12
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    • pp.1296-1305
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    • 2009
  • This paper has the object of investigating dynamic stability of stiffened tapered thick plate with concentrated mass on Pasternak foundation by means of finite element method and providing kinematic design data for mat of building structures. Finite element analysis of stiffened tapered thick plate is done by use of rectangular finite element with 8-nodes. In order to analysis plate which is supported on Pasternak foundation, the Winkler foundation parameter is varied with 10, 100, 1000 and the shear foundation parameter is 5, 10, concentrated mass is $0.25m_c$, $1.0m_c$, tapered ratio is 0.25, 0.5. The ratio of In-plane force to critical load is applied as $0.4\sigma_{cr},\;0.6\sigma_{cr},\;0.8\sigma_{cr}$ respectively. This paper analyzed varying tapered ratio.

Dynamic Stability Analysis of Tapered Thick Plate on varying Concentrated Mass (집중질량 크기 변화해 따른 변단면판의 동적안정해석)

  • Kim, Il-Jung;Oh, Soog-Kyoung
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.127-132
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    • 2007
  • This paper has the object of investigating dynamic stability of opening thick plates on Pasternak foundation by means of finite element method and providing Kinematic design data for mat of building structures. Finite element analysis of Tapered Thick plate is done by use of rectangular finite element with 8-nodes. In order to analysis plate which is supported on Pasternak foundation. the Winkler foundation parameter is varied with $10^2$, $10^3$ and the shear foundation parameter is 5, 10. The ratio of force to critical load is applied as 0.4, 0.6, respectively. This paper analyzed varying Tapered Ratio and Concentrated Mass.

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A Study on Combination Technology of a Transformer and a Superconducting Fault Current Limiter (변압기와 초전도한류기의 결합기술 연구)

  • Choi, Hyo-Sang
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.3
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    • pp.330-334
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    • 2010
  • We tried to combine a transformer with a superconducting element and investigated the current limiting characteristics. When a superconducting element was connected to third winding of the transformer, the fault current was limited to about 90 % effectively. The fault current and consumption power were able to be controlled by the turn's ratio of secondary and third windings. It gives flexibility of the rating of a transformer in the power grid. As a result, power burden of a superconducting element was reduced by the decrease of turn's ratio in third winding of a transformer. It was because the voltage behavior of a superconducting element was dependent on turn's ratio of a transformer while the current characteristic was independent.