• 제목/요약/키워드: Direct Boundary Element Method

검색결과 100건 처리시간 0.037초

반무한 방음벽의 삽입손실의 이론과 BEM해석에 의한 결과치 비교 (Comparison of the Insertion Loss Results of Semi-infinite Plane Screen by the Analytical Method and Boundary Element Method)

  • 김문섭;김관주
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 1995년도 추계학술대회논문집; 한국종합전시장, 24 Nov. 1995
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    • pp.25-31
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    • 1995
  • 본 연구는 방음벽의 성능예측을 위해 BEM의 접근 방법을 시도하였으며 범용 음향 소프트웨어인 Sys-noise 5.2의 direct collocation bem을 사용하여 반무한 평면 방음벽에 대한 해석을 수행하였으며, 그 결과를 검증하기 위해 Maekawa에 의한 근사해와 해석적 점근해에 비교하였다. 또한, 수음점이 방음벽으로부터 떨어진 거리, 방음벽의 폭, 방음벽의 높이에 따른 삽입손실을 계산하였고, 방음벽에 흡음처리를 한 경우와 방음벽상단의 형상변화에 따른 삽입손실의 변화를 계산하였다.

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유한영역에서의 모드 III 꺾인균열 해석을 위한 적분방정식 적용연구 (AN INTEGRAL EQUATION FOR KINKED CRACKS APPLIED TO MODE III IN FINITE PLANE BODIES)

  • Sur, Ukhwan
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제2권1호
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    • pp.111-129
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    • 1998
  • An integral equation representation of cracks was presented, which differs from well-known "dislocation layer" representation. In this new representation, an integral equation representation of cracks was developed and coupled to the direct boundary-element method for treatment of cracks in plane finite bodies. The method was developed for in-plane(modes I and II) loadings only. In this paper, the method is formulated and applied to mode III problems involving smooth or kinked cracks in finite region. The results are compared to exact solutions where available and the method is shown to be very accurate despite of its simplicity.

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Design Sensitivity Analysis of Coupled Thermo-elasticity Problems

  • Choi Jae-yeon;Cho Seonho
    • Journal of Ship and Ocean Technology
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    • 제8권3호
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    • pp.50-60
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    • 2004
  • In this paper, a continuum-based design sensitivity analysis (DSA) method is developed for the weakly coupled thermo-elasticity problems. The temperature and displacement fields are described in a common domain. Boundary value problems such as an equilibrium equation and a heat conduction equation in steady state are considered. The direct differentiation method of continuum-based DSA is employed to enhance the efficiency and accuracy of sensitivity computation. We derive design sensitivity expressions with respect to thermal conductivity in heat conduction problem and Young's modulus in equilibrium equation. The sensitivities are evaluated using the finite element method. The obtained analytical sensitivities are compared with the finite differencing to yield very accurate results. Extensive developments of this method are useful and applicable for the optimal design problems incorporating welding and thermal deformation problems.

자동 격자 생성법과 설계 요소를 이용한 형상 최적 설계에 관한 연구 (A Study on the Optimal Shape Design Using Automatic Regridding and Design Element)

  • 김호룡;단병주
    • 한국정밀공학회지
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    • 제10권3호
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    • pp.87-96
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    • 1993
  • In this study, the peak stress of a fuillet in elastic structure was optimized to have minimum value by using quadratic isoparametric element. The method of auomatic gridding was also developed along with shape algorithm and design element technique was adopted in selecting design variables. The computer program developed was combined with the Hooke-Jeeves direct algorithm of optimization techniques in order to minimize the peak stress of the fillet. The imployment of design element technique significantly cut down computer time by the reduction in design variables, and the opitmum fillet shape with uniform minimum stress was obtained by varying design variables along x and y directions in improving the shape compared to other results. By using automatic gridding, in which Bezier surfaces and Coons surfaces of cubic interpolation were employed, the irregular boundary was removed resulting in smoother anbd more accurate fillet shape possessing uniform minimum stress.

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Elastic analysis of arbitrary shape plates using Meshless local Petrov-Galerkin method

  • Edalati, H.;Soltani, B.
    • Wind and Structures
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    • 제27권4호
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    • pp.235-245
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    • 2018
  • In this study the stress analysis of orthotropic thin plate with arbitrary shapes for different boundary conditionsis investigated. Meshfreemethod is applied to static analysis of thin plates with various geometries based on the Kirchhoff classical plate theory. According to the meshfree method the domain of the plates are expressed through a set of nodes without using mesh. In this method, a set of nodes are defined in a standard rectangular domain, then via a third order map, these nodes are transferred to the main domain of the original geometry; therefore the analysis of the plates can be done. Herein, Meshless local Petrov-Galerkin (MLPG) as a meshfree numerical method is utilized. The MLS function in MLPG does not satisfy essential boundary conditions using Delta Kronecker. In the MLPG method, direct interpolation of the boundary conditions can be applied due to constructing node by node of the system equations. The detailed parametric study is conducted, focusing on the arbitrary geometries of the thin plates. Results show that the meshfree method provides better accuracy rather than finite element method. Also, it is found that trend of the figures have good agreement with relevant published papers.

2차원 유한요소해석을 통한 선형 유도전동기의 종방향 단부효과 고려를 위한 1-d direct solution의 검증 (Verification of 1-d direct solution for longitudinal end effect occurred in linear induction motor by using 2-d FEM)

  • 이성구;함상환;이형우;이주
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2009년도 춘계학술대회 논문집
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    • pp.978-983
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    • 2009
  • This paper analyzed longitudinal end effect occurred in linear induction motor by using I-d direct solution and its result is verified by 2-d Finite Element Method(FEM). Longitudinal end effect of linear induction motor caused by magnetic discontinuity in primary core and electric discontinuity in armature winding has been investigated by many researchers. In this paper, 1-d direct solution and boundary conditions proposed by Yamamura and Nasar is used to analyze end effect of linear induction motor and its solution is verified by 2-d FEM.

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강성분포의 변화가 초대형 부유식 구조물의 유탄성응답에 미치는 영향 고찰 (Influences of Stiffness Distributions on Hydroelastic Responses of Very Large floating Structures)

  • 김병완;경조현;홍사영;조석규
    • 대한조선학회논문집
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    • 제42권3호
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    • pp.220-232
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    • 2005
  • Influences of stiffness distributions on hydroelastic responses of very large floating structures (VLFS) are studied in this paper. Hydroelastic responses are calculated by direct method employing higher-order boundary element method (HOBEM) for fluid analysis and finite element method (FEM) for structure analysis. In structural analysis using FEM, Mindlin plate elements are used. An 1 km-long VLFS with uniform stiffness and modified VLFS with varying stiffness distributions are considered in numerical analysis. Responses of VLFS increase in flexible parts and decrease in stiff Parts. Reduction degree of displacements of VLFS with stiffened center is larger than that of VLFS with stiffened sides.

주기적 변형 경계조건을 적용한 면내 유효 탄성 물성치의 계산 (Evaluation of Effective In-Plane Elastic Properties by Imposing Periodic Displacement Boundary Conditions)

  • 정일섭
    • 대한기계학회논문집A
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    • 제28권12호
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    • pp.1950-1957
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    • 2004
  • Analysis for structures composed of materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. In order to evaluate the effective properties, a unit cell is defined and loaded somehow, and its response is investigated. The imposed loading, however, should accord to the status of unit cells immersed in the macroscopic structure to secure the accuracy of the properties. In this study, mathematical description for the periodicity of the displacement field is derived and its direct implementation into FE models of unit cell is attempted. Conventional finite element code needs no modification, and only the boundary of unit cell should be constrained in a way that the periodicity is preserved. The proposed method is applicable to skew arrayed in-homogeneity problems. Homogenized in-plane elastic properties are evaluated for a few representative cases and the accuracy is examined.

기하형상의 임의교란이 음향산란에 미치는 영향 (Effect of Random Geometry Perturbation on Acoustic Scattering)

  • 주관정
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 1992년도 추계학술대회논문집; 반도아카데미, 20 Nov. 1992
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    • pp.117-123
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    • 1992
  • In recent years, the finite element method has become one of the most popular numerical technique for obtaining solutions of engineering science problems. However, there exist various uncertainties in modeling the problems, such as the dimensions(geometry shape), the material properties, boundary conditions, etc. The consideration for the uncertainties inherent in the problems can be made by understanding the influences of uncertain parameters[1]. Determining the influences of uncertainties as statistical quantities using the standard finite element method requires enormous computing time, while the probabilistic finite element method is realized as an efficient scheme[2,3] yielding statistical solution with just a few direct computations. In this paper, a formulation of the probabilistic fluid-structure interaction problem accounting for the first order perturbation of geometric shape is derived, and especially probabilistical acoustic pressure scattering from the structure with surrounding fluid is focused on. In Section 2, governing equations for the fluid-structure problems are given. In Section 3, a finite element formulation, based on the functional, is presented. First order perturbation of geometric shape with randomness is incorporated into the finite element formulation in conjunction with discretization of the random fields in Section 4 and 5. Finally, the proposed formulation is applied to a acoustic pressure scattering problem from an infinitely long cylindrical shell structure with randomness of radial perturbation.

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파랑하중을 받는 부유체의 강성에 따른 응답 고찰 (Response Analysis of Floating Structure under Wave Loads Considering Stiffness)

  • 김병완;김영식;홍사영;경조현;조석규
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2006년도 정기 학술대회 논문집
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    • pp.941-948
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    • 2006
  • In this paper, the effect of stiffness on hydroelastic responses of plate-like floating structure under wave loads are studied. Direct method is used for the numerical analysis. In the numerical analysis, structural equation is formulated by finite element method(FEM) and higher order boundary element method(HOBEM) is employed for the analysis of fluid flow. A 1000m-long VLFS(Very Large Floating Structure) is considered in numerical analyses. By analyzing VLFS for various cases of stiffness, the characteristics of hydroelastic responses with the variation of stiffness are investigated.

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