• 동력기계공학회지
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• 제9권4호
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• pp.71-76
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• 2005

Marine structures are often in contact with inner or outer fluid as stern, ballast and oil tanks. The effect of interaction between fluid and structure has to be taken into consideration when we estimate the dynamic response of the structure appropriately. Fatigue damages can also be sometimes observed in these tanks which seem to be caused by resonance. Thin walled tank structures in ships which are in contact with water and located near engine or propeller where vibration characteristics are strongly affected by the added mass of containing water. Therefore it is essentially important to estimate the added mass effect to predict vibration characteristics of tank structures. But it is difficult to estimate exactly the magnitude of the added mass because this is a fluid-structure interaction problem and is affected by the free surface, vibration modes of structural panels and the depth of water. I have developed a numerical tool of vibration analysis of 3-dimensional tank structure using finite elements for plates and boundary elements for fluid region. In the present study, the effect of added mass of containing water, the effect of structural constraint between panels on the vibration characteristics are investigated numerically and discussed. Especially a natural frequencies by the fluid interaction between 2 panels and a breath mode of the water tank are focused on.

• 콘크리트학회논문집
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• 제14권4호
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• pp.530-539
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• 2002

전단벽의 연성도 확보를 위한 단부횡보강 설계에 있어서, 현재 설계기준들은 경험적이며 강제적이다. 즉, 현재 설계기준은 연성도 요구량에 관계없이 단부횡보강영역과 상세를 정해 놓고 있으며, 따라서 성능기초설계에 부적합하다. 본 연구의 목적은 성능기초설계에 적합한 전단벽의 연성도 설계방법을 개발하는 것이다. 단부횡보강영역에 따른 전단벽의 연성도변화를 조사하기 위하여 실험연구를 수행하였으며 압축대를 모델링하기 위하여 각기 다른 횡보강영역을 갖는 시험체에 편심축하중을 가력하였다. 실험연구를 통하여 횡보강된 벽체 압축대의 강도, 연성도, 파괴모드 등을 연구하였으며, 벽체 단면 전체에서 단부 횡보강으로 인하여 발생하는 연성도 및 파괴시점을 조사하기 위하여 비선형 수치해석을 수행하였다. 실험과 해석연구 결과를 기반으로 하여 전단벽의 연성도 설계방법을 개발하였다. 제안된 설계방법을 이용하여, 주어진 연성도 요구량에 맞게 단부횡보강영역과 횡보강량을 정확히 결정할 수 있으며, 따라서 벽체의 연성거동을 보장하는 동시에 경제적인 벽체설계가 가능하게 되었다.

• 한국소음진동공학회논문집
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• 제23권6호
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• pp.537-545
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• 2013

In this paper, the vibration for actuators having lens module, confined to lateral and torsional directions of suspensions, is described by mathematically analyzing its suspension configuration and motion. In order to prove the accuracy of this result, it is compared to a finite element analysis. Also it is shown that modal frequencies can be modified by changing design parameters in mathematical motion expressions.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.127-132
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• 2010

Eigensolutions associated with self-excited vibration of disc brake system can be obtained by complex eigenvalue analysis. The eigenvalue sensitivity to change in contact stiffness can be used to demonstrate stability criteria and eigenvalue veering. Dynamic instability on eigenvalue loci with respect to the variation of contact stiffness is found to be related to mode interaction between two adjacent modes. This modal interaction can be effectively shown by mode shape visualization. This paper presents the methodology to construct the mode shape of disc brake system where a disc and two brake pads are coupled with contact stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1995년도 추계학술대회논문집; 한국종합전시장, 24 Nov. 1995
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• pp.191-196
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• 1995

지지부에 비틀림 하중을 받는 Elstica는 비틀림 운동을 하며, 그 가진 주파수가 굽힘모드 근처일 때는 해당하는 굽힘 모드의 운동까지도 동시에 존재하게 된다. 이때 가진력의 크기가 작을때는 주기적인 운동이 된다. 가진력의 크기가 증가함에 따라 굽힘 운동은 굽힘 1차 모드와 연성된 유사주기운동이 발생하며, 이떤 범위 이상이 되면 굽힘 운동과 비틀림 운동이 결합된 진폭이 매우 크고 불규칙적인 비평면 운동(out of plane motion)이 발생하게 되며 이 때의 운동은 혼돈운동이다. Elastica가 굽힘 3차 고유진동수 근방의 주파수로 비틀림 하중을 받을 때의 정확한 이론적 해석을 위해서는 굽힘 3차모드 까지는 반영할 수 있는 식이 모델링 되어야 할 것으로 보인다. 이것은 복잡한 비평면운동을 할 때 굽힘 3차 모드까지 관찰된다는 사실에 근거한다.

• 한국음향학회지
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• 제34권5호
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• pp.360-370
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• 2015

무한 길이를 가진 도파관 구조물에 유한 길이를 가진 구조물이 결합되어 있는 경우, 결합된 구조물의 응답을 수치해석으로 구하기 위해서는 파동 방법과 모드 방법을 함께 적용하여 해석하는 것이 필요하다. 본 논문에서는 무한 길이 도파관구조물에 대해서는 파수유한요소법을, 유한 길이 구조물에 대해서는 유한요소법을 적용하여 결합 지점에서의 각 하부 구조물 임피던스 또는 모빌리티를 구하고 이를 연성하여 전체 구조물의 응답을 해석하는 방법에 대하여 다루었다. 해석 대상 구조물로는 내부에 사각 평판 구조물이 네 꼭지점에서 결합되어 있는 무한 길이 원통형 실린더를 선정하였으며, 네 결합지점이 강결합 또는 탄성마운트로 결합된 경우에 대하여 살펴보았다. 본 연구를 통해 임피던스 연성을 통한 파동 방법(파수유한요소법)과 모드 방법(유한요소법)의 결합이 적용 가능함을 확인하였다.

• 소음진동
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• 제11권1호
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• pp.132-140
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• 2001

The vibratory gyroscope can effectively measure the angular velocity as the oscillating and position-sensing mode are exactly tuned. The veering Phenomenon impedes the exact tuning, which is caused by the mode coupling of two modes. In this paper, the gyroscope's structure with two frames is introduced to minimize the veering phenomenon that destabilizes the tuning process of oscillating and position-sensing mode. Experimental results show that the Proposed structure can achieve the mode intersection without veering phenomenon.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.73-78
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• 2013

In this paper, the vibration for a pickup actuator is described by mathematically analyzing its suspension configuration and motion, confined to lateral and torsional directions of suspensions. In order to prove the accuracy of this result, it is compared to a finite element analysis. Also it is shown that modal frequencies can be modified by changing design parameters in mathematical motion expressions.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.95-106
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• 2001

When the crankshaft of diesel engine has more than 3 throws, which are arranged in a different plane, its vibration induces coupled motions, especially the coupled torsional and axial vibration. Nowadays, the torsional vibration which is influenced rather weak than axial one, can be theoretically calculated fairly accurately, but theoretical calculation results of the axial vibration which is influenced strongly from torsional vibration is not so good. To get accurate calculation results of axial vibration, coupled axial-torsional vibration must be treated. In this investigation, coupled effects of vibration of diesel engine propulsion shafting are analyzed theoretically and some simple calculation methods are also studied. On this first report, effects of coupling on natural frequencies and their modes are mainly studied, setting the each mass in 4 degrees of freedom.

• 소음진동
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• 제9권4호
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• pp.822-827
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• 1999

The reduction of booming noise level and improvement of sound quality in the vehicle interior have been major fields of vehicle NVH for many years. In order to reduce the booming noise this paper proposed a system variable, which takes account of mode shapes and natural frequencies of the structural-acoustic system, measurement points and excitation frequency. By simplifying the system variable, the major contributors of panels inculding roof, roof lining, wind shield glasses, doors and floor to booming noise at a specific frequency was experimentally found. Also the relationships between structural modes of roof lining, one of the major contributors, and acoustic modes of compartment cavity were investigated from the viewpoint fo structure-borne noise. In addition, the roof lining was modified structurally by applying marble sponge to the gap between roof and roof lining. Asthe result of structural modification, the booming noise was reduce at target frequency.