• Title/Summary/Keyword: 유한요소정식화

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An NDE Method using Tapping Sound based on High Precision Computation (정밀수치해석을 기반으로 한 태핑음 비파괴 검사법)

  • 황준석;김승조
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.10a
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    • pp.195-198
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    • 2003
  • 정밀 수치해석으로 구한 태핑음 데이터를 기준으로 하여 복합재료 구조물 내의 층간분리 손상의 존재 여부를 판단하는 비파괴 검사법을 제안하였다. 태핑음의 수치 모사를 위해 동적 접촉 알고리듬을 이용한 유한요소법과 경계요소법을 이용하였다. 태핑음 수치해석 과정에 대한 정식화를 수행하고 실제 구조물의 태핑음과 비교하여 수치해석 기법의 타당성을 밝혔다. 웨이브릿 페킷 변환에 근거한 특성 추출법을 이용하여 태핑음으로부터 손상 판단을 위한 특성을 추출하고 손상 판단의 지표가 되는 특성 지수를 정의하였다. 복합재료 구조물에 대한 층간분리 손상 검출과정을 시연함으로써 제시된 태핑음 검사법의 타당성을 밝혔다.

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Tearing Test for Automotive Vibroisolating Rubber and Formulation of Tearing Energy (자동차용 방진고무의 찢김시험 및 찢김에너지 정식화)

  • Moon, Hyung-Il;Kim, Heon Young;Kim, Min Gun;Kim, Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.12
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    • pp.1669-1674
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    • 2012
  • A commonly analytical estimation of fatigue life on rubber components is using fatigue life equation based on various fatigue test results. However, such method has very restricted applicability in actual designing processes because performing fatigue tests requires a lot of time and money. In addition, non-standard rubber materials and their randomness make it hard to make databases. In this paper, the other fatigue life estimation method using tearing energy was suggested. We performed static and dynamic tearing test about automotive vibration rubber materials and a finite element formulation using a virtual crack to calculate the tearing energy of rubber components with complicated shapes. To using the suggested method, fatigue life of an automotive motor mount has been estimated and verified the reliability of this method by using comparison between the estimated values and the actual fatigue life.

Performance Analysis of LIPCA Actuator considering Material Non-linearity of embedded PZT wafer (압전 세라믹의 재료 비선형성을 고려한 LIPCA 작동기의 성능 해석)

  • Lee, Sang-Ki;Kim, Young-Sung;Park, Hoon-Cheol;Yoon, Kwang-Joon;Goo, Nam-Seo;Cho, Chahng-Min
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.3
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    • pp.37-44
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    • 2004
  • This paper deals with the performance analysis of LIPCA(Light-weight Piezo-Composite actuator) including the material nun-linearity of the embedded 3203HD PZT wafer. For this analysis, we used a piezo-shell element code based on a nine-node assumed strain shell element formulation. The material non-linearity was implemented in the formulation due to a large observed discrepancy between the measured displacement and the computed actuation displacement based on the linear analysis. An experimentally extracted piezo-strain function of the PZT wafer and incremental formulation were incorporated into the linear finite element code to improve the accuracy of the estimated actuation displacement of the LIPCA. The non-linear piezo-shell program was used to predict the non-linear performance of the LIPCA. The simulated actuation displacement from the non-linear code showed much better agreement with the measured data.

Dynamic Characteristics of Anisotropic Laminated Plates (이방성 복합재료의 동적특성에 관한 연구)

  • Park, Sungjin;Baek, Jooeun
    • Journal of the Society of Disaster Information
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    • v.12 no.1
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    • pp.62-68
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    • 2016
  • In this study, the impact problems are brought up and the formulation by isoparametric element is attempted for the purpose of analyzing the response characteristics of laminated plate receiving impact load based on the first-order shear deformation theory expanded from the Mindlin plate theory. The result of static analysis and dynamic analysis is drawn through the numerical analysis rectangular and circular plates of antisymmetric Angle-Ply laminated plate using the finite element method and the analysis on each displacement is compared.

Volume Integral Expressions for Numerical Computation of the Dynamic Energy Release Rate (동적(動的)에너지 방출율(放出率)의 수치해석(數値解析)을 위한 체적적분식(體積積分式))

  • Koh, Hyun Moo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.9 no.3
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    • pp.65-73
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    • 1989
  • Continuum formulations for the expressions of dynamic energy release rates and computational methods for dynamic stress intensity factors are developed for the analysis of dynamic fracture problems subjected to stress wave loading. Explicit volume integral expressions for instantaneous dynamic energy release rates are derived by modeling virtual crack extensions with the dynamic Eulerian-Lagrangian kinematic description. In the finite element applications a finite region around a crack-tip is modeled by using quarter-point singular isoparametric elements, and the volume integrals are evaluated for each crack-tip element during virtual crack extensions while the singularity is maintained. It is shown that the use of the present method is more reliable and accurate for the dynamic fracture analysis than that of other path-independent integral methods when the effects of stress waves are significant.

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Ship Structural Reliability Analysis by Probabilistic Finite Element Method (확률 유한요소법에 의한 선체 구조 신뢰성해석)

  • S.J. Yim;Y.S. Yang;J.H. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.241-250
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    • 1991
  • The reliability analysis for web frame of tanker is carried out by the probabilistic finite element method combined with the classical reliability method such as MVFOSM and AFOSM which can be used for calculating the probability of failure for the complicated structures in which the limit state equation is implicitly expressed. As random variables external load, elastic modulus, sectional moment of inertia and field stress are chosen and Parkinson's iteration algorithm in AFOSM is used for reliability analysis. By adding only the covariance data of the random variables to the input data set required for conventional finite element method, the present method can easily calculate the probability of failure at every element end as well as the covariances of structural reponses such as displacements at every element end and member forces at every element, even for the complicated ship structure.

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Moving Support Elements for Dynamic Finite Element Analysis of Statically Determinate Beams Subjected to Support Motions (지점운동을 받는 정정보의 동해석을 위한 동지점 유한요소 개발)

  • Kim, Yong-Woo;Jhung, Myung Jo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.4
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    • pp.555-567
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    • 2013
  • A finite element formulation for a Rayleigh-damped Bernoulli-Euler beam subjected to support motions, which accompanies quasi-static rigid-body motion, is presented by using the quasi-static decomposition method. Moving support beam elements, one of whose nodes is coincident with the moving support, are developed to represent the effect of a moving support. Statically determinate beams subjected to support motions can be modeled successfully by using moving support elements. Examples of cantilever and simply-supported beams subjected to support motions are illustrated, and the numerical results are compared with the analytical solutions. The comparison shows good agreement.

A Multi-noded Cable Element Considering Sliding Effects (슬라이딩을 허용하는 다절점 케이블요소)

  • Kim, Moon Young;Lee, Jun Seok;Han, Man Yop;Kim, Sung Bo;Kim, Nak Kyung
    • Journal of Korean Society of Steel Construction
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    • v.17 no.4 s.77
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    • pp.449-457
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    • 2005
  • A multi-noded cable element allowing sliding at its nodes without frictions was introduced in this paper, and its elastic stiffness matrix was derived. A two-node truss element was briefly summarized and extended to multi-node, cable-truss elements that keep their tension constant but are connected without frictions through several nodes. The element elastic stiffness matrix of the multi-node,cable-truss elements was consistently derived. The steel wales pre-stressed externally in the IPS system were chosen as numerical examples and analyzed under various loading conditions. The cable tensions calculated using the present element were compared with the results of the flexibility method and those using the two-node truss element, respectively.

A 9-node Degenerated Shell Element for Inelastic Analysis of Reinforced Concrete Structures (철근 콘크리트 구조물의 비탄성 해석을 위한 9절점 퇴화 쉘 요소)

  • 이상진;서정문
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.4
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    • pp.481-494
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    • 2001
  • An enhanced degenerated shell finite element (FE), which has been developed for inelastic analysis of reinforced concrete structures is described in this paper. Generally, Reissner-Mindlin (RM) assumptions are adopted to develop the degenerated shell FE so that transverse shear deformation effects is considered. However, it is found that there are serious defects such as locking phenomena in RM degenerated shell FE since the stiffness matrix has been overestimated in some situations. As remedies of locking phenomena, reduced integration, incompatible mode and assumed strain method have been used. Especially, the assumed strain method has been successfully used in many FEs. But contrarily, there is a few investigation on the performance of the assumed strains in the inelastic analysis of concrete structures. Therefore, shell formulation is provided in this paper with emphasis on the terms related to the stiffness matrix based on assumed strain method and microscopic concrete material model. Finally, the performance of the present shell element is tested and demonstrated with several numerical examples. From the numerical tests, the present result shows a good agreement with experimental data or other numerical results.

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Finite Element Analysis of Eddy Current Testing for Tubes with 3-Dimensional Defects (3차원 관결함에 대한 와전류탐상의 유한요소해석)

  • Lee, Hyang-Beom;Won, Sung-Yean;Shin, Young-Kil
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.3
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    • pp.191-199
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    • 2000
  • In this paper, a numerical analysis using the finite element method (FEM) is presented which models the eddy current testing (ECT) of tubes with 3-dimensional defects. For the description of 3-dimensional eddy current problems, the governing equation is derived from the Maxwell's equations. The 3-dimensional FEM formulation with hexahedral elements is carried out using the Galerkin weighted residual method. The INCONEL 600 steam generator tube with inner and outer diameter defects is adopted for the numerical analysis, and the ECT signal, which is the trajectory of the probe impedance, is calculated. For the verification of the numerical analysis method, results of numerical calculations and experiments are compared and they show good agreements. Based on this verification, several defect signals are predicted and their characteristics are investigated with the variation in the defect depth and the circumferential angle of the defect.

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