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A DAMAGE IDENTIFICATION METHOD FOR THIN CYLINDRICAL SHELLS
오혁진(H. Oh),조주용(J. Cho),이우식(U. Lee) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the dynamic equations of the damaged cylindrical shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM requires only the FRF-data measured in damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.
최혁진(H.J.Choi),오상우(S.W.Oh),이승국(S.G.Lee),이승현(S.H.Lee),김선동(S.D.Kim),강원수(W.S.Kang),이승훈(S.H.Lee) 한국해양환경·에너지학회 2006 한국해양환경공학회 학술대회논문집 Vol.2006 No.-
본 논문은 침몰선박으로부터 잔존유를 원격으로 회수할 수 있는 장비의 개발결과와 해상시운전 결과에 대해서 제시한다. 개발된 침몰선박 잔존유 무인회수시스템은 최대수심 200미터에서 침몰선체에 구멍을 뚫어, 유압펌프를 이용하여 선체 내부의 잔존유를 선상으로 회수할 수 있는 장비이다. 수중의 모든 작업이 무인으로 선상에서 제어되므로, 안정적이고 신뢰성 있는 수중작업을 위해서, 수중의 주요작동장치에 입력대비 출력이 우수한 유압작동방식을 선정하였으며, 제어부분에는 마이크로 컨트롤러를 사용하여 여러 장치를 효율적 통합적으로 제어할 수 있도록 하였다. 개발된 시스템의 종합적인 성능시험을 위해서, 울산해역 수심 74미터에서 해상 시운전을 실시하였고, 이를 통해서 시스템의 안정성을 확인하였다. This paper introduces the underwater system which is able to recover the remained oil from sunken ships by remote control. This system can recover the remained oil from a tank of the ship by drilling and pumping method. Because all parts of system are remotely operated by controller on the ship, it is essential to make the system stable and reliable. So, the hydraulic actuators having the large output are adapted to this system and by using the micro controller, this system can be controlled more efficiently. For the test of performance, the site experiment was carried out in 74 meter underwater of the East Sea near Ulsan, Korea. Through this test, we certified the stability of this system.
최혁진(H.J.Choi),오상우(S.W.Oh),이승국(S.G.Lee),김선동(S.D.Kim),이승현(S.H.Lee),이문진(M.J.Lee),변성훈(S.H.Byun),강원수(W.S.Kang),장석(S.Jang) 한국해양환경·에너지학회 2006 한국해양환경·에너지학회 학술대회논문집 Vol.2006 No.-
유조선 경신호는 1988년 포항 대보등대 3.5마일 해상에 침몰하였다. 침몰후 현재까지도 간헐적으로 잔존유가 유출되고 있어 선체내부에 남아 있는 잔존유의 추가 유출에 따른 해양오염사고 발생에 대한 위험성이 재기되고 있다 침몰선체로부터 잔존유 추가 유출 가능성을 조사하기 위해 2006년 5월 무인잠수정과 잔존유 시료채취장치 등 첨단 장비를 이용하여 경신호를 조사한 결과 선체 주변에는 이미 많은 장애물로 덮여 있으며, 잔존유 시료를 채취한 결과 탱크 내부에는 약 300㎘ 이상의 기름이 남아 있는 것으로 분석되었으며, 부식 등의 요인으로 잔존유 유출시 기상상태에 따라 차이는 있으나 1988 사고 당시와 같은 기상상태가 재현된다면 유출된 기름은 포항, 영덕 등 인근 해안가에 부착될 가능성이 있다. The oil tanker, Kyung Shin had sunken in the East Sea, 3.5 mile from Daebo light house of Pohang, Korea in 1988. Because the remained oil of the sunken tanker has been leaking slightly nowadays, it can be a dangerous marine pollutant. For the inspection of additional oil leakage and its possibility, the sunken ship, Kyung Shin was surveyed by using the ROV and oil sampling system in May, 2006. As a result of survey, there are numbers of obstructions on the tanker's body. Based on the survey results and the precedent salvage report, more than 300㎘ oil could be remained by estimation. If same weather condition is reappeared, spilled oil can stick to the coast near Pohang and Yeongdeok.
침몰선박 정밀 조사 작업을 위한 수중 위치추적시스템의 설치 및 활용
변성훈(S. H. Byun),최혁진(H. J. Choi),오상우(S. W. Oh),이승국(S. G. Lee) 한국해양환경·에너지학회 2006 한국해양환경·에너지학회 학술대회논문집 Vol.2006 No.-
An acoustic positioning system (APS) was introduced to MOERI/KORDI as a part of the unmanned oil recovery system developed for the prevention of oil spill from a sunken ship. It supports both the ultra short baseline (USBL) and the long baseline (LBL) modes for positioning underwater vehicles so that it can provide versatile performance to various on-site situations. After a week-long sea trial in the East sea last year, it was put in practical use for the on-site surveys of sunken ships near Ulsan and Pohang this year and successfully supported the whole activities of the underwater vehicles of the unmanned oil recovery system. This paper presents some techniques used for installing the APS and gives the positioning results obtained during the on-site survey of the sunken ships. Analysis of the positioning data shows that the underwater vehicles were tracked with 0.7 m rms error horizontally and 0.3 m rms error in depth using USBL without initial calibration.
음향전달함수(ATF)를 이용한 부밍 소음 취약부 예측 연구
황광현(K.H. Hwang),오혁진(H.J. Oh),최승찬(S.C. Choi),서진관(J.K. Suh),홍석길(S.G. Hong) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
The noise and vibration have been evaluated by using the finite element model in the vehicle developing stage. The sound pressure of the vehicle compartment is predicted by the acoustic cavity model coupled with the body structure. In general, the structural model has been focused to study in the improvement of the noise. It is not easy to treat the structural model, instead the acoustic cavity model is relatively simple and aids in root cause analysis of vibro-acoustic issues. Therefore, the acoustic transfer function of the cavity is more efficient for finding out the main contribution parts of the vehicle booming noise. And examples about the run-up booming noise demonstrate the validity of the AFT analysis for improving the vibro-acoustic sensitivity.
오정환(J-H Oh),강성길(S-G Kang),최혁진(H-J Choi),이문진(MJ Moon),박경(Kyeng Park) 한국해양환경·에너지학회 2004 한국해양환경공학회 학술대회논문집 Vol.2004 No.-
A suspended sediment (SS) transport model is developed and internally linked to the CH3D-WES model. The model is based on the mass-balance equations for three size classes representative of the Upper Chesapeake Bay. The first class (3 m) consists of fine particles that are in more or less continual suspension in water column and thus constitute the background concentration. The second class (18 m) consists of medium particles that are alternately eroded and deposited by tidal current and the last class (65 m) of coarse particles that stay at the bed most of the time. No interaction among size classes and no effect of the SS on the hydrodynamic field are assumed. The present model employs an empirical formulation to account for depth-limited erosion by varying the critical shear stress for erosion. ceo as a function of eroded mass. The model is applied to the Upper Chesapeake Bay to simulate annual conditions in 1996. The model is calibrated against acoefficient in the formulation of depth-limited erosion with the intensive data in Sanford et al. (2001) and verified with the Chesapeake Bay Program monitoring data. The three size classes appear to behave as they are intended to and the model gives a reasonable reproduction of the data. not only for intertidal but for intratidal variations in salinity and SS concentration.
수중탱크내 액체물질 시료채취시스템 개발 및 해상 시운전
오상우(S.W.Oh),최혁진(H.J.Choi),이승국(S.G.Lee),이승훈(S.H.Lee) 한국해양환경·에너지학회 2006 한국해양환경·에너지학회 학술대회논문집 Vol.2006 No.-
해상에서의 선박의 침몰 및 해상 운송물의 유실로 인해 유해액체물질을 저장하고 있는 탱크가 수중에 격리되어 있을 경우, 이는 유출가능성을 가지고 있는 잠재적인 환경 오염원이다. 본 논문에서는 유해액체물질의 잔존유무 및 잔존량을 확인할 수 있는 새로운 무인시료채취장치의 개발결과와 해상 시운전 결과를 기술한다. 개발된 장비의 모든 동작은 선상에서 원격으로 조종되며, 무인잠수정(ROV)과의 연동작업을 통해서 최대수심 200M에서, 액체시료를 채취할 수 있다. 개발된 장비는 1988년 포항 해역에 침몰한 경신호를 대상으로, 총 3회의 잔존유 시료채취작업을 성공적으로 수행함으로써, 시스템의 성능을 입증하였다. In case the tanker having the noxious liquid substance is sunken and isolated by accident in the sea, it can be a potential marine pollutant. This paper suggests the novel underwater sampling system which can inspect the existence and quantity of remained liquid. All functions of this system are controlled by remote control and this system can sample the liquid from the liquid reservoir in the 200 meter underwater. This system sampled the remained oil three times from the sunken ship 'Kyung-shin' which has been sunken in the East Sea near Pohang in 1998. Through this sea trial, we proved the performance of this system.
오상우(S.W. Oh),최혁진(H.J. Choi),김진민(J.M. Kim) 한국해양환경·에너지학회 2009 한국해양환경·에너지학회 학술대회논문집 Vol.2009 No.11월
본 연구는 수중 유연관의 변형 정도를 광섬유 마이크로벤드 센서를 이용하여 측정하는 방법에 관한 것으로, 연구를 통해 새롭게 설계한 광섬유 마이크로벤드 센서를 이용하여 수중 유연관의 굽힘의 정도를 감소된 광신호 크기를 통해 해석한 실험결과를 제시한다. 제안된 마이크로벤드 센서는 기존의 센서와는 다르게 단일 구조로 유연관의 양방향 굽힘에 대해 동일한 크기의 마이크로벤드 손실을 광섬유에 발생시킬 수 있는 장점을 갖고 있어, 여러 방향으로 굽힘 변형이 일어날 수 있는 수중 유연관으로의 적용에 효율적이다. This research is about the measuring technique of underwater tube's bending degree and presents an experimental result performed by novel designed fiber optic microbend sensor. Through the experiment, it was found that the optical power loss increased as the bending degree of tube increased. Because the suggested sensor can generate same level of microbend effect at the both directional bend of underwater tube, it is efficient to be applied to the underwater tube which tends to be multidirectionally bended.