• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.173-178
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• 2001

부분구조 합성법(substructuring or substructure synthesis)은 부분구조(substructure)의 주파수 응답함수(FRFs, frequency response functions)를 이용하여 합성된 전체 구조물의 동특성(dynamic behavior)을 파악하는 기술로서 이에 관한 이론은 명확하며 간단하다. 즉, 역행렬 계산과 같은 기본적인 행렬연산으로 부분구조 합성을 수행한다. 그러나, 여러 가지 요인으로 인하여 계산된 합성 결과는 실제로 결합된 전체 구조물의 동특성과는 차이를 보인다. 현실적인 이유로 고려하지 못하는 회전자유도와 실험에서 수반되는 여러 가지 측정오차는 주요한 요인이며 이에 대한 연구 또한 많이 진행되었다. 본 연구에서는 이러한 요인 중, 상대적으로 덜 중요하게 평가된 모드자름 오차(modal truncation error)의 영향을 고려한다. 단순한 구조물에 대하여 모의실험을 수행함으로써, 모드자름 오차로 인하여 완전히 잘못된 합성 결과가 나을 수 있다는 것을 보인다. 측정된 FRE를 이용하여 이러한 오차를 보정(compensation)하는 소개하고 이를 대상 구조물에 적용하여 모드자름 오차의 영향을 상당히 줄일 수 있다는 것을 보인다. 복잡한(complicated) 구조물에 대하여 모드자름 오차의 영향을 줄이기 위해서 모든 FRFs를 보정하는 것은 어려우므로 현실적인 대안을 모색한다.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.359-368
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• 2018

Dynamic analysis of complex and large structures may be costly from a numerical point of view. For coupled vibroacoustic finite element models, the importance of reducing the size becomes obvious because the fluid degrees of freedom must be added to the structural ones. In this paper, a component mode synthesis method is proposed for large vibroacoustic interaction problems. This method couples fluid subdomains and dynamical substructuring of Craig and Bampton type. The acoustic formulation is written in terms of the velocity potential, which implies several advantages: coupled algebraic systems remain symmetric, and a potential formulation allows a direct extension of Craig and Bampton's method to acoustics. Those properties make the proposed method easy to implement in an existing finite element code because the local numerical treatment of substructures and fluid subdomains is undifferentiated. Test cases are then presented for axisymmetric geometries. Numerical results tend to prove the validity and the efficiency of the proposed method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.95-102
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• 1995

Procedures for estimation of axial or flexural rigidities of bridge members by neural networks are shown. To treat large scale structures containing many unkwon parameters, substructuring concept is introduced. The measurement points are selected considering the sensitivity of the element stiffnesses of interest. Utilization of relative mode vectors is found to be very effective for the local parameter estimation. Then, the study focuses on the method to obtain the training set enough to represent structures. It is shown that noise injection is effective to reduce the estimation errors caused by measurement noise. Verification of the present method is carried out using a cable-stayed bridge model.

• 한국전산구조공학회논문집
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• 제12권2호
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• pp.233-241
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• 1999

본 연구는 개별 메모리를 갖는 소결합 구조의 MIMD형 병렬컴퓨터인 트랜스퓨터시스템 하에서 구조최적화를 위한 병렬처리 과정을 보이고 시험모델에 적용하여 타당성 및 효율성을 검증한다. 전체 최적화과정의 대부분을 차지하는 해석 및 민감도 알고리즘은 영역단위의 병렬성을 갖는 부구조화에 근거하고 하드웨어 구성에 맞춰 변환 재구성한다. 각 노드간 통신은 정적응축과 설계도함수에 한정, 그 횟수를 최소화하고 그들을 동기화하므로써 개별메모리형 연산모델의 약점인 통신비용의 문제를 해소한다. PC를 호스트로 한 수치실험은 고속화 효율성 면에서 고무적인 결과를 보여주고 있으며, 이런 점에서 시스템의 확장성을 함께 고려한다면 트랜스퓨터 시스템에 기초한 병렬처리는 공학 환경의 변화와 요구에 부응하는 좋은 대안이 될 수 있다.

• Animal cells and systems
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• 제1권4호
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• pp.535-538
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• 1997

Allozyme variation of seven enzyme systems was analyzed from 202 individuals from four Korean populations of Atractomorpha lata. These populations exhibit higher levels of values of in most other insects with a mean 64% of polymorphic loci and a mean 0.384 of expected heterozygosity within populations. Fixation indices indicated considerable substructuring within populations sampled (mean $F_{is}=0.403)$, indicating probable inbreeding or assortative mating coupled with restricted migration between subpopulations. This was supported by the field observation that the species exists as small, discrete colonies in meadow habitats and females carry males. In addition, significant differences in allere frequencies between males and females at polymorphic loci examined (70%, 16 of 23 cases) could account for the observed heterozygote deficiencies.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.124-132
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• 2000

Distributed processing approach for structural optimization is presented in this study. It is implemented on network of personal computers. The validity and efficiency of this approach are demonstrated and verified by test model of truss. Repeated structural analysis algorithm, which spend a lot of overall structural optimization processes, are based on substructuring scheme with domain-wise parallelism and converted to be adapted to hardware and software environments. The design information data are modularized and assigned to each computer in order to minize the communication cost. The communications between nodes are limited to static condensation and constraint-related data collection.

• 한국전산구조공학회논문집
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• 제12권1호
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• pp.57-66
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• 1999

국부진동에 의하여 영향을 받는 일부 부재를 분석하기 위하여 구조물 전체의 대하여 동적해석을 수행하는 것은 비경제적일 수 있다. 본 논문에서는 국부진동의 효율적인 해석을 위하여 부분구조법을 사용하였다. 선택된 부재의 해석에 사용할 경계조건을 구하기 위하여 자유도를 응축하는 행렬응축기법을 사용하였다. 해석의 정당성을 검토하기 위하여 경계조건을 고정지지와 단순지지한 경우와 비교하였다. 본 연구에서 제시한 부분구조기법을 이용하면 가진층에 대해서는 효율적으로 매우 정확한 거동을 예측할 수 있지만, 가진층에서 멀리 떨어진 곳에 대한 거동 예측 시에는 다소 오차가 발생한다.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3782-3791
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• 1996

A great deal of effert has been invested in upgrading the performance and the efficiency of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, this performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircraft, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure based on that of the composing structures, are widely used. By llinking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned structures can be desinged. In this paper, a new algorithm for structural dynamic modification-SRFSM (substructure response function sensitivity method) is proposed by linking frequency responce function synthesis and response function sensitivity. A mehtod to obtain response function sensitivity using direct derivative of mechanical impedance, is also used.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.201-206
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• 2000

In this work transfer function synthesis method based on FRF data of each substructure is investigated for a complex structure composed of many substructures. Though the transfer function synthesis method has superiority to analyze the characteristics of interfaces among substructures effectively, many problems arise in the computation process, especially matrix inversion process. Due to computational problems, the error between the data obtained by test and the predictions through computations is inevitable. So in this paper, computational aspects in the transfer function synthesis method are examined through a steering system problem of passenger car. For the FBS method, frequency response functions of 3 substructures are measured experimentally. Effects of several parameters such as matrix inversion method, connection conditions between substructures and off-diagonal terms on system response are studied numerically.

• Structural Engineering and Mechanics
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• 제7권6호
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• pp.575-588
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• 1999

A boundary element method is applied to the analysis of crack trajectory in materials with complex microstructure, such as discontinuously reinforced composite materials, and systems subjected to complex loading, such as indentation. The path followed by the crack(s) has non-trivial geometry. A study of the stress intensity factors and fracture toughness of such systems must therefore be accompanied by an analysis of crack trajectory. The simulation is achieved using a dual boundary integral method in planar problems, and a single boundary integral method coupled with substructuring in axisymmetric problems. The direction of crack propagation is determined using the maximum mechanical energy release rate criterion. The method is demonstrated by application to (i) a composite material composed of components having the elastic properties of aluminium (matrix) and silicon carbide (reinforcement), and (ii) analysis of contact damage induced by the action of an indenter on brittle materials. The chief advantage of the method is the ease with which problems having complex geometry or loading (giving rise to complex crack trajectories) can be treated.