• 대한토목학회논문집
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• 제12권1호
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• pp.43-50
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• 1992

본(本) 연구의 목적(目的)은 평면응력/변형과 축대칭 및 쉘문제를 포함하는 다양한 응용문제에서 계층적(階層的) 성질을 갖는 적분형 르장드르 형상함수에 의한 P-version 모델의 통용성(通用性)을 확인하는 것이다. 현대 유한요소 해석에서 정확도를 확보하지 못하는 가장 큰 이유는 비(非)압축성 재료와 망목(網目)설계시 요소의 형상비(形狀比), 사다리꼴 요소에서 변(邊)의 감소비(減少比)와 평행사변형 요소의 왜곡도(歪曲度) 등을 갖는 불규칙 형상에서 나타나는 가상메카니즘과 Locking 현상이다. 조건수(條件數)와 에너지 노름이 계산오차, 수렴성 및 알고리즘의 효율성을 검증하는데 사용되었으며 해석결과는 NASTRAN과 SAP90 및 Cheung이 제안한 Hybrid 요소와 비교되었다. NASTRAN을 제외한 SAP90 및 P-version 프로그램은 16 Bit 소형컴퓨터에 의해 실행되었다.

• 한국자동차공학회논문집
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• 제2권1호
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• pp.116-127
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• 1994

A method using the linear matrix algebra is developed in order to determine unknown external forces in linear structural analyses. The method defines a matrix which represents the linearity of the vibrational analysis for a structural system. The unknown external forces are determined by the operations of the matrix. The method is applied to find an engine motion in an automobile system. For a simulation process, an exhaust system is modeled and analyzed by the finite element method. The validity of the simulation is verified by comparing with the experimental results the free vibration. Also, an experiment on the forced vibration is performed to determine the damping ratio of the exhaust sysetm. Estimated model parameters(natural frequency, mode shape) are in accord with the experimental results. Because the method merely repeats the transpose and inverse operations of a matrix, the solution is extremely easy and simple. Moreover, it is more accurate than the existing methods in that there is no artificial assumptions in the calculation processes. Therefore, the method is found to be reliable for the analysis of the exhaust system considering the characteristics of vibrations. Although the suggested method is tested by only the exhaust system here, it can be applied to general structures.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.21-32
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• 1994

The Problem of mechanical vibration is investigated for an automotive exhaust system. The vibrational reduction effect is systematically evaluated according to the attachment of the exhaust system. Moreover, the optimal attachment position of bellows is determined from the viewpoint of vibration isolation. The structure is analysed by the finite element technique where the geometry, the mass, the stiffness and the damping properties of the exhaust pipe are modeled. The validity of the developed model is verified by comparing with the experimental results. An optimization is carried out by the quadratic approximation algorithm. The reaction transferred to an automobile body by the hanger is considered ad the objective function. It is shown that the exhaust system which has the bellows at the optimal position is more effective for the vibrational characteristics than the others. It is also proved that this analytical method is quite useful in the design stage of the exhaust system.