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풍력발전기 복합재 블레이드의 접착 분리 모니터링을 위한 패키징 광섬유 브래그 격자 센서 탐촉자의 사용성 검토
권일범(Il-Bum Kwon),최기선(Ki-Sun Choi),김근진(Geun-Jin Kim),김동진(Dong-Jin Kim),허용학(Yong-Hak Huh),윤동진(Dong-Jin Yoon) 한국비파괴검사학회 2011 한국비파괴검사학회지 Vol.31 No.4
최근 대형화되는 복합재 풍력 블레이드의 운전 중 발생되는 손상을 조기에 모니터링하기 위하여 블레이드 내부에 일체형으로 설치가 가능한 스마트 센서들이 연구되고 있다. 본 연구애서는 광섬유 브래그 격자(FBG: Fiber Bragg grating) 센서를 복합재 모형 블레이드 후연부 시편에 부착하여 균열 또는 접착층 분리를 강지하는 실험을 수행하여 패키징된 광섬유 브래그 격자 센서 탐촉자의 풍력 블레이드에 적용 가능성을 검토하였다. 블레이드 시편에 인가된 인장 하중이 1100 N부터 1260 N 사이에서 노출된 광섬유 브래그 격지 센서의 파장 이동 방향이 급격히 반전되는 결과로부터 전단 웹의 균열과 접착 분리 파손을 확인할 수 있었다. 블레이드에 사용하기 위한 노출된 광섬유 브래그 격자 센서는 깨지기 쉽기 때문에 이 단점을 보완하기 위하여 에폭시로 패키징된 광섬유 브래그 격자 센서 탐촉자를 제작하였다. 블레이드 시편의 스킨 위에 제작된 탐촉자를 설치한 후 인장 시험을 수행한 결과 변형률에 대한 감지도는 약 1.3 με/pm으로 노출된 광섬유 브래그 격자 센서의 감지도와 거의 동일한 것으로 확인되었다. 한편 온도 감지도는 80℃까지의 가열 테스트를 통하여 약 48 pm/℃의 온도 감지도를 보였다. Smart sensors embedable in composite wind turbine blades have been required to be researched for monitoring the health status of large wind turbine blades during real-time operation. In this research, the feasibility of packaged FBG sensor probes was studied through the experiments of composite blade trailing edge specimens in order to detect cracking and debonding damages. The instants of cracking and debonding generated in the shear web were confirmed by rapid changes of the wavelength shifts from the bare FBG sensor probes, Packaged FBG sensor probes were proposed to remove the fragile property of bare FBG sensor probes attached on composite wind blade specimens. Strain and temperature sensitivity of fabricated probes installed on the skin of blade specimen were almost equal to those of a bare FBG sensor. Strain sensitivity was measured to be 1.3 με/pm in a strain range from to 0 to 600 με, and the calculated temperature sensitivity was to be 48 pm/℃ in the heating test up to 80 degree.
광섬유 마이켈슨 센서에 의한 축소모형 강트러스 교량의 변형률 측정
권일범 ( Kwon Il-bum ),최만용 ( Choi Man-yong ),문한규 ( Moon Hahngue ) 한국구조물진단유지관리공학회 1998 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.2 No.1
The strains of a steel truss bridge, which was scaled down to 1/15 of the real bridge for the laboratory experiments, were measured to monitor the health status of the bridge by quadrature phase-shifted 3x3 fiber optic Michelson sensors. The fiber optic sensors and electrical strain gages were bonded on the surface of some frames to sense the strain pattern induced by the abnormal structural behavior. The fiber optic signals were immediately processed by personal computer for the strain determination. In order to confirm the strain sensitivity of the fiber optic sensors, these fiber optic strains were compared with the strains of the strain gages. The static behavior of the bridge was analyzed by finite element analysis with SaP2000. These unite element analysis results were compared with the structural strain pattern obtained by the electrical strain gages and were arranged with the database for the determination of the bridge health condition. It was shown that the breakage of some frames could be detected from the changes in strain pattern.
권일범 ( Kwon Il-bum ),최만용 ( Choi Man-yong ),김민수 ( Kim Min-soo ) 한국구조물진단유지관리공학회 1999 한국구조물진단유지관리공학회 논문집 Vol.3 No.3
Recently, there has been considerable interest in the development of fiber-optic sensors based on fiber Bragg gratings (FBGs), which can be made into Ge-doped fiber’s core by UV phase mask or holographic methods. A good sensitivity and small size of this sensor make it an ideal candidate for distributed sensing in smart structures or other structural monitoring applications. In this study, fiber optic Bragg grating sensor, which could be applied to measure the absolute strains, was constructed and the strain sensitivity of this sensor was investigated in order to apply to the structural health monitoring. Fiber Fabry-Perot (FFP) filter has been used to detect the optical signals instead of optical spectrum analyzer. It has been convenient to determine the structural strains from the output signal of FBGs. The fiber optic Bragg grating sensor was attached on the aluminum beam near the electrical strain gage to measure the same strain. The relationship between strain and fiber signal was linearly fitted. The strain sensitivity of the fiber optic Bragg grating sensor was determined as 1.57 με/μsec from the aluminum beam test.
대형 구조물의 변형률 측정을 위한 광섬유 TR-EFPI 센서의 개량
권일범 ( Kwon¸ Il-bum ),최만용 ( Choi¸ Man-yong ),김치엽 ( Kim¸ Chi-yeop ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.2
The sensor for continuous in-situ monitoring is better to be embedded in large structures. Fiber optic sensors can be embedded in the structures to get the health information in the structures. Fiber optic EFPI(extrinsic Fabry-Perot interferometric) sensors had been shown in many publications which concerned about the structural strain measurement. However, the gage lengths of the sensors in these papers were limited at about 1 cm because it is very difficult to make the long gage length fiber optic EFPI sensor. If the gage length of the fiber optic EFPI sensor could be made as long as about 90 mm, then the sensitivity is to be more higher than the short gage length fiber sensor at about 9 times. In this study, the fiber optic TR-EFPI (total reflected - extrinsic Fabry-Perot interferometric) sensor was developed and was improved to be get the long gage length about 90 mm. The loading-unloading test was performed to confirm the performance of the improved fiber optic TR-EFPI sensor. In this experiment, the strain which was determined by the fiber optic signal had some errors. It was considered that this errors caused by the sliding mismatch in the sensor probe.
광섬유 브래그 격자 센서가 있는 광섬유 라인에 라만 OTDR을 이용한 분포 온도 및 변형률 측정 가능성에 대한 연구
권일범(Il-Bum Kwon),변종현(Jong-Hyun Byeon),전민용(Min-Yong Jeon) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.6
한 개의 감지 광섬유 라인으로 분포 온도와 몇 개의 변형률을 측정할 수 있는 새로운 광섬유 센서연구를 수행하였다. 분포 온도는 감지 광섬유의 라만 안티-스토크스 산란광을 시간영역 반사계(OTDR: optical time domain reflectometry)로 측정하고, 변형률은 광섬유 브래그 격자(FBG: fiber Bragg grating)를 사용하여 측정하였다. 분포 온도는 4 km의 단일 모드 광섬유의 감지 광섬유로부터 안티-스토크스 후방 산란광을 양방향에서 취득하고 새로이 고안된 수식으로 온도를 계산하였다. 온도 실험은 감지 광섬유의 중간쯤에서 약 50 m의 광섬유 부분의 온도를 30℃부터 70℃까지 10℃ 간격으로 변화시키면서 실험한 결과 온도 측정 오차 범위는 0.50℃이하로 확인되었다. 또한 감지 광섬유에 설치된 FBG는 변위 스테이지로 변형시키고 파장 변화를 광학 스펙트럼 분석기로 측정한 결과 각각 0.10 nm, 0.17 nm, 0.29 nm, and 0.00 nm를 얻었다. 이러한 파장이동은 각각 85.76µϵ, 145.55 µϵ, 247.86µϵ, 0.00 µϵ에 해당되었다. In this study, we propose a novel fiber optic sensor to show the measurement feasibility of distributed temperature and strains in a single sensing fiber line. Distributed temperature can be measured using optical time domain reflectometry (OTDR) with a Raman anti-Stokes light in the sensing fiber line. Moreover, the strain can be measured by fiber Bragg gratings (FBGs) in the same sensing fiber line. The anti-Stokes Raman back-scattering lights from both ends of the sensing fiber, which consists of a 4 km single mode optical fiber, are acquired and inserted into a newly formulated equation to calculate the temperature. Furthermore, the center wavelengths from the FBGs in the sensing fiber are detected by an optical spectrum analyzer; these are converted to strain values. The initial wavelengths of the FBGs are selected to avoid a cross-talk with the wavelength of the Raman pulsed pump light. Wavelength shifts from a tension test were found to be 0.1 nm, 0.17 nm, 0.29 nm, and 0.00 nm, with corresponding strain values of 85.76µϵ, 145.55µϵ, 247.86µϵ, and 0.00µϵ, respectively. In addition, a 50 m portion of the sensing fiber from 30℃ to 70℃ at 10℃ intervals was used to measure the distributed temperature. In all tests, the temperature measurement accuracy of the proposed sensor was less than 0.50℃.