• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.595-601
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• 2003

For monitoring of the civil and building structure, optical fiber sensors are very convenient. The fiber sensors are very small and do not disturb the structural properties. They also have several merits such as electro-magnetic immunity, long signal transmission, good accuracy and multiplicity of one sensor line. Strain measurement technologies with fiber optic sensors have been investigated as a part of smart structure. In this paper, we investigated the possibilities of fiber optic sensor application to the monitoring of beam-column joints of structures. We expect that the fiber optic sensors replace electrical strain gauges. The commercial electric strain gauges show good stability und dominate tile strain measurement market. However, they lack durability and long term stability for continuous monitoring of the structures. In order to apply the strain gauges, we only have to attach them to the surfaces of the structures. In this paper, we investigate the possibility of using fiber optic Bragg grating sensors to joint structure. The sensors show nice response to the structural behavior of the joint.

• 센서학회지
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• 제26권6호
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• pp.391-396
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• 2017

Human body motion detection is important in several industry sectors, such as entertainment, healthcare, rehabilitation, and so on. In this paper, we first discuss commercial human motion detection technologies (optical markers, MEMS acceleration sensors, infrared imaging, etc.) and then explain recent advances in the development of flexible and stretchable strain sensors for human motion detection. In particular, flexible and stretchable strain sensors that are fabricated using carbon nanotubes, silver nanowires, graphene, and other materials are reviewed.

• 한국항공우주학회지
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• 제33권3호
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• pp.32-38
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• 2005

FBG 센서는 다중화의 큰 장점으로 인해 다른 여러 광섬유 센서에 비해 더욱 활발한 연구가 진행 되어오고 있다. FBG 센서는 센서 피크 신호의 파장 이동량을 감지함으로써 변형률, 온도 등의 물리량을 측정하는 복조기법을 가지고 있다. 하지만, 센서를 구조물에 부착 혹은 삽입 적용하는 과정에서 구조물의 기하학적인 특성이나 결함 등에 의해 구조물에 변형률 구배가 발생할 수 있으며 이는 센서의 격자 부분에 작용할 경우 센서 피크 신호의 안정성에 영향을 미처 측정 오차로 작용하게 된다. 본 연구에서는 FBG 센서의 격자 부분에 변형률 구배가 작용할 경우 변형률 구배에 따른 FBG 센서의 신호 특성을 고찰하였고 또한 격자의 길이와 변형률 구배의 상관관계에 대해 알아보았다. 이를 통해, 변형률 구배가 작용할 경우 FBG 센서의 적절한 사용 영역을 FBG 센서의 격자 길이에 따라 정량적으로 제시하였다.

• Composites Research
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• 제34권6호
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• pp.387-393
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• 2021

본 논문에서는 습식 식각으로 제작된 구리 전극을 가진 다중벽 탄소나노튜브 PDMS 복합재료 변형율 센서의 전기적 특성을 고찰하였다. MWCNT의 질량분율에 따라 MWCNT-PDMS 변형율 센서를 제작한 후, 전극 부착 표면을 습식 식각한 후 은-에폭시 전도성 접착제를 이용하여 구리 박판을 부착하였다. 2-프로브 방법으로 변형율 센서의 전기 전도성을 측정한 결과, 초기 저항은 MWCNT 함량과 식각 시간에 반비례하였지만 30% 변형율에 대한 저항 변화율은 MWCNT 함량과식각 시간에 비례하였다. 100회 반복 하중 시험 후 저항 변형율 감소는 MWCNT 함량이 증가할수록 식각 시간이 짧아질수록 상대적으로 작게 나타났다. 이는 식각에 의해 MWCNT-PDMS 변형율 센서의 초기 저항 감소에 기인한 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.295-299
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• 1996

Intrinsic Fabry-Perot Optical fiber sensors were embedded to tensile side of the 20cm$\times$20cm$\times$150cm cement concrete structures. The sensors were attached to the reinforcing steels and then, the cement concretes were applied. It took 30 days for curing the specimens. After that, the specimens were tested with 4-point bending method by universal testing machine. Strains were measured and recorded by the strain gauges embedded near optical fiber sensors. Output data of fiber sensor showed good linearity to the strain data from the strain gauges up 2000microstrain. The optical fiber sensors showed good response after yielding of structure while embedded metal film strain gauges did not show any response. We also specimens were broken down. In conclusion, the optical fiber sensors can be used as elements of health monitoring systems for cement concrete infra-structures.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.218-221
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• 2009

This paper reports on measurement method for the fiber optic strain monitoring of overhead contact line systems of trains, We used FBG (Fiber Bragg Grating) sensors to measure the strain variation of overhead contact line. FBG sensors can sensitively measure the variation of strain and! or temperature by the shift wavelength of reflected wave according to the lattice variation during the measurement. FBG sensor were attached on the contact line and connected to the monitoring system with optical fibers. The monitering system with FBG sensors showed very good sensitivity to measuring strain variation and this system could be applied to the overhead contact line of KTX (Korea Train eXpress).

• 센서학회지
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• 제30권3호
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• pp.181-184
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• 2021

Interest in healthcare and wearable devices has been increasing recently. A strain sensor is required in various wearable devices. With respect to such devices, studies on resistance changes in strain sensors using flexible materials are in progress. However, the resistance of the rest area in a strain sensor should not change according to the applied strain. So, an electrode with resistance to stretching, bending, and torsion is required in such strain sensors. Tension, bending, and torsion can be realized through structural shape control, rather than by using flexible materials. Further, such an electrode that maintains electrical properties has been developed and manufactured. This electrode can be used in various applications such as foldable devices, e-papers, batteries, and multifunctional wearable devices.

• 센서학회지
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• 제25권4호
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• pp.247-251
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• 2016

Au/PDMS membranes are widely used to fabricate strain sensors which can detect input signals. An interfacial adhesion between metal films and polydimethylsiloxane (PDMS) substrates is one of the important factors determining the performance of strain sensors, in terms of robustness, reliability, and sensitivity. Here, we fabricate Au/PDMS membranes with (3-mercaptopropyl) trimethoxysilane (MPTMS) treatment. PDMS membranes were fabricated by spin-coating and the thickness was controlled by varying the spin rates. Au electrodes were deposited on the PDMS membrane by metal sputtering and the thickness was controlled by varying sputtering time. Owing to the MPTMS treatment, the interfacial adhesion between the Au electrode and the PDMS membrane was strengthened and the membrane was highly transparent. The Au electrode, fabricated with a sputtering time of 50 s, had the highest gauge factor at a maximum strain of ~0.7%, and the Au electrode fabricated with a sputtering time of 60 s had the maximum strain range among sputtering times of 50, 60, and 120 s. Our technique of using Au/PDMS with MPTMS treatment could be applied to the fabrication of strain sensors.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.159-166
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• 2006

Although the strain distribution along the length of a beam in buildings or infrastructures is non-uniform, most fiber optic sensors are point sensors that can measure the strain only at a local point of a beam. Long gage fiber optic sensors that measure integrated strain over a relatively long length can consider strain variation. This type of sensor was found to be efficient and useful for monitoring large-scale structures. On the other hand, the maximum strain or stress in a beam can not be measured with long gage optic sensors. However, for the assessment of the safety of multi-span steel beams subjected to various vertical loads, the maximum strain or stress measured during monitoring is required for comparison with the allowable stress of the beam calculated by a design code. Therefore, in this paper, mathematical models are presented for determination of the maximum values of strains in more three-span steel beams based on the average strains measured by long gage optic sensors.

• Smart Structures and Systems
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• 제18권3호
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• pp.405-423
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• 2016

In this study, the feasibility of using telecommunication single-mode optical fiber (SMF) as a distributed fiber optic strain and crack sensor was evaluated in concrete pavement monitoring. Tensile tests on various sensors indicated that the $SMF-28e^+$ fiber revealed linear elastic behavior to rupture at approximately 26 N load and 2.6% strain. Six full-scale concrete panels were prepared and tested under truck and three-point loads to quantify the performance of sensors with pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). The sensors were protected by precast mortar from brutal action during concrete casting. Once air-cured for 2 hours after initial setting, half a mortar cylinder of 12 mm in diameter ensured that the protected sensors remained functional during and after concrete casting. The strains measured from PPP-BOTDA with a sensitivity coefficient of $5.43{\times}10^{-5}GHz/{\mu}{\varepsilon}$ were validated locally by commercial fiber Bragg grating (FBG) sensors. Unlike the point FBG sensors, the distributed PPP-BOTDA sensors can be utilized to effectively locate multiple cracks. Depending on their layout, the distributed sensors can provide one- or two-dimensional strain fields in pavement panels. The width of both micro and major cracks can be linearly related to the peak strain directly measured with the distributed fiber optic sensor.