• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.224-231
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• 2008

A subway or an underground railway is one of the representative public transportations which lots of people take everyday. Then, subway station, which is also one of the very important public civil infrastructures, generally services for a long period of time. During the service time of stations, they are easily damaged from environmental corrosion, material aging, fatigue, and the coupling effects with long-term loads and extreme loads. Recently, civil construction work on the places near station often creates lots of damages to the station. As these damages accumulate, the performance of station degenerates due to the above factors. They would inevitably reduce the resisting capacity of station against the disaster; even they bring into the collapse of stations with the structural failure under long-term loads and extreme loads. And, if disaster such as earthquake, fire, etc. happens, it causes huge property damage and threatens the human lives. Because of these above reasons, the structural health monitoring system need to be developed for ensuring the safety of station. In this paper, the development directions of the structural health monitoring system with fiber optic sensor and USN for subway station are briefly described.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.442-458
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• 2014

Wave induced vibrations increase the fatigue and extreme loading, but this is normally neglected in design. The industry view on this is changing. Wave induced vibrations are often divided into springing and whipping, and their relative contribution to fatigue and extreme loading varies depending on ship design. When it comes to displacement vessels, the contribution from whipping on fatigue and extreme loading is particularly high for certain container vessels. A large modern design container vessel with high bow flare angle and high service speed has been considered. The container vessel was equipped with a hull monitoring system from a recognized supplier of HMON systems. The vessel has been operating between Asia and Europe for a few years and valuable data has been collected. Also model tests have been carried out of this vessel to investigate fatigue and extreme loading, but model tests are often limited to head seas. For the full scale measurements, the correlation between stress data and wind data has been investigated. The wave and vibration damage are shown versus heading and Beaufort strength to indicate general trends. The wind data has also been compared to North Atlantic design environment. Even though it has been shown that the encountered wind data has been much less severe than in North Atlantic, the extreme loading defined by IACS URS11 is significantly exceeded when whipping is included. If whipping may contribute to collapse, then proper seamanship may be useful in order to limit the extreme loading. The vibration damage is also observed to be high from head to beam seas, and even present in stern seas, but fatigue damage in general is low on this East Asia to Europe trade.

• 자동차안전학회지
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• 제12권1호
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• pp.52-61
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• 2020

In recent years, the increasing interest in health-care requires the industrial products to be well-designed ergonomically. In the commercial vehicle industry, several researchers have demonstrated the driver's posture has great effect on the orthopedic desease such as fatigue, back pain, scoliosis, and so on. However, the existing sensor systems developed for measuring the driver posture in real time have suffered from inaccuracy and low reliability issues. Here, we suggest our smart vehicle seat system capable of real-time driver posture monitoring by using the air bag sensor package with high sensitivity and reliability. The ergonomic numerical model which can evaluate a driver's posture has been developed on the basis of the human body segmentation method followed by simulation-based validation. Our experimental analysis of obtained pressure distribution of a vehicle seat under the different driver's postures revealed our smart vehicle system successfully achieved the driver's real-time posture data in great agreement with our numerical model.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.171-176
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• 1999

Nondestructive inspection and accompanying life analysis based on fracture mechanics were the major conventional methods for evaluating remaining life of critical high temperature components in power plants. By using these conventional methods, it has been difficult to perform in-service inspection for life prediction. Also, quantitative damage evaluation due to unexpected abrupt changes in operating temperature was almost impossible. Thus, many efforts have been made for evaluating remaining life during operation of the plants and predicting real-time life usage values based on the shape of structures, operating history, and material properties. In this study, a core software for on-line life monitoring system which carries out real-time life evaluation of a critical component in power boiler(high temperature steam headers) is developed. The software is capable of evaluating creep and fatigue life usage from the real-time stress data calculated by using temperature/stress transfer Green functions derived for the specific headers and by counting transient cycles. The major benefits of the developed software lie in determining future operating schedule, inspection interval, and replacement plan by monitoring real-time life usage based on prior operating history.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2008년도 추계학술대회 논문집
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• pp.93-102
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• 2008

An energy based crack growth model is developed in this study to simulate the propagation of top-down cracking in asphalt pavements. A viscoelastic fracture mechanics approach, generalized J integral, is employed to model the crack growth of asphalt concrete. Laboratory fatigue crack propagation tests for three different asphalt mixtures are performed at various load levels, frequencies and temperatures. Disk-shaped specimens with a proper loading fixture and crack growth monitoring system are selected for the tests. It is observed from the tests that the crack propagation model based on the generalized J integral is independent of load levels and frequencies, while the traditional Paris' law model based on stress intensity factor is dependent of loading frequencies. However, both models are unable to take care of the temperature dependence of the mixtures. The fatigue crack propagation model proposed in this study has a good agreement between experimental and predicted crack growth lives, which implies that the energy based J integral could be a better parameter to describe fatigue crack propagation of viscoelastic materials such as asphalt mixtures.

• 한국통신학회논문지
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• 제37권8C호
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• pp.711-720
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• 2012

본 논문에서는 운전자 졸음 인식 시스템의 구현 방법과 그에 따른 결과를 소개한다. 영상 입력 장치로는 시중에 판매되는 웹캠 카메라를 사용하였다. 얼굴 검출 방법으로는 Haar 변환 기법을 이용하였으며, 다양한 조명 환경에 강건하게 적응하도록 조명정규화를 수행하였다. 조명정규화를 거친 얼굴 영상은 특징값 추출에 용이하다. 조명정규화를 통한 눈 후보영역은 인체측정학 정보를 이용하여 후보 영역을 줄인 이후에 PCA와 Circle Mask의 혼합 모델을 적용했다. 위 방법을 통해 차량 내부의 복잡한 조명 환경 속에서 강건히 눈 영역을 추출한다. 검출된 눈 영역은 고해상도의 조명 정규화 영상과 간단한 연산을 통하여 졸음 여부를 판별한다. 졸음 상태가 1단계로 판단 될 경우에는 통합 모니터링 인터페이스에서 운전자에게 경고음을 울리며 2단계일 경우에는 CAN(Controller Area Network)를 통하여 안전벨트를 진동하게 함으로써 운전자에게 경고를 준다. 본 논문에서 제안하는 졸음 인식 시스템은 낮은 계산 복잡도를 만족하는 동시에 높은 인식률을 보여준다. 실험 결과 차량 내에서 97%의 인식률이 나타났다.

• Smart Structures and Systems
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• 제29권6호
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• 에너지공학
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• 제8권4호
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• pp.605-611
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• 1999

화력발전설비 고온요소의 잔여수명평가는 주로 비파괴검사 및 검사결과의 파괴역학적 해석등으로 행해졌다. 그러나 기존 방법은가동중에는 적용되기 어렵고 급작스런 운전이력에 대한 정량적인 손상을 평가할 수 없었다. 따라서 구조물의 형상, 운전이력 및 재료물성에 근거하여 실시간 수명소비율 및 잔여수명을 평가하는 기술의 개발이 요구되고 있다. 본 연구에서는 고온 증기헤더의 수명을 실시간으로 평가하는 감시시스템 소프트웨어를 개발하였다. 고온헤더에 대하여 해석된 온도, 응력, 그린함수를 이용하여 취약부위의 실시간 응력을 계산하고 천이 사이클을 카운트하여 크리프 및, 피로수명을 계산하였다. 본 소프트웨어를 개발함으로써 운전이력에 따른 소비수명을 실시간으로 평가하고 운전정보를 기록하여 향후 운전계획, 보수주기 및 교체시기를 결정하는데 지침이 되도록 하였다.

• 비파괴검사학회지
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• 제36권6호
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• pp.496-503
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• 2016

발전소나 석유화학 플랜트 구조물에 누설이 발생하면 인명 피해 및 경제적인 손실을 초래한다. 이러한 누설은 플랜트 배관의 진동으로 인한 피로파괴나 배관 감육으로 인해 발생한다. 플랜트 배관의 진동을 감시하기 위한 방법으로 주로 가속도센서나 레이저센서가 사용되지만 설치 및 운용의 어려움이 따르고 동시에 광범위 측정 시 비용 증가가 발생하게 된다. 이러한 문제점들을 해결하기 위해 최근 카메라를 이용한 누설 및 진동 변위 측정 방법에 대한 연구가 이루어지고 있다. 카메라를 이용한 누설 및 진동 변위 측정 방법은 설치가 간단하고 원거리 측정 및 넓은 범의의 측정이 가능한 장점을 가지고 있다. 따라서 본 연구에서는 카메라를 이용해 누설 및 진동 변위를 측정할 수 있는 시스템을 개발하였고 실험을 통해 성능을 검증하였다.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.65-75
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• 2015

Among the destruction instances of half-through arch bridges, the shorter hangers are more likely to be ruined. For a thorough investigation of the hanger system durability, we have studied vehicle impact effect on hangers with vehicle-bridge coupling method for a half-through concrete-filled-steel-tube arch bridge. A numerical method has been applied to simulate the variation of dynamic internal force (stress) in hangers under different vehicle speeds and road surface roughness. The characteristics and differences in impact effect among hangers with different length (position) are compared. The impact effect is further analyzed comprehensively based on the vehicle speed distribution model. Our results show that the dynamic internal force induced by moving vehicles inside the shorter hangers is significantly greater than that inside the longer ones. The largest difference of dynamic internal force among the hangers could be as high as 28%. Our results well explained a common phenomenon in several hanger damage accidents occurred in China. This work forms a basis for hanger system's fatigue analysis and service life evaluation. It also provides a reference to the design, management, maintenance, monitoring, and evaluation for this kind of bridge.