• 한국정밀공학회지
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• 제11권2호
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• pp.32-40
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• 1994

In this study by using EMAT(electro magnetic acoustic transducer)the artificial slit is installed on 12B-SUS pipe test piece. By making 4 cycle SH-burst (EMA) incidence to 45 .deg. angle, the signal data of pulse, received from EMAT are translated into digital-signal-processing- method SSP(Split Spectrum Processing) and Deconvolution method. The main conclusions obtained are as follows; (1) the signal data received from EMAT are translated with digital signal proc- essing of SSP-method and Deconvolution-method and this method shows exellent results more than Ultrasonic testing method does; (2) noise can well be removed by SSP with signal data, and resolution and S/N ratio are advanced; (3) when used with Ultrasonic wave general stainless steel has proporties of multiscattering and reflection phenomena, but resolution is progressed by using Deconvolution method;and (4) as addition-averaging-processing mumber is increasing, the resolution and S/N ratio are improved and the satisfactory signal is obtained.

• 한국해양공학회지
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• 제20권2호
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• pp.8-15
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• 2006

Guided-waves-based mortar-filled steel pipe inspection is carried out through using EMAT (Electro magnetic acoustic transducer) and wavelet transform. Possibly existing anomalies such as separation (or void) and inclusion are made in the fabricated mortar-fled steel pipes: these anomalies are infected. Since guided waves have the long range inspection capability, EMAT has its own advantages over the conventional PZT (Piezoelectric zirconate titanate), and wavelet transform gives the multi-resolution on time-frequency domain results, the suggested technique gives an alternative way for inspecting mortar-filled steel pipes, which are popularly used for supporting marine structures such as piers, wharfs, moles, and dolphins. Through this study, it is show that the suggested technique is promising for detecting the amounts of separations and inclusions.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.595-601
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• 2005

A mobile robot system utilizing NDT (Non-Destructive Testing) method is designed and fabricated f3r automatic integrity evaluation of large sized industrial reservoirs and pipelines. The developed mobile robot can crawl over the outer surface of the industrial facilities even though the shape of the structures is various and unsymmetric. The robot detects defects such as pinholes, cracks and thickness reduction at the wall of the facilities using EMAT (Electro-Magnetic Acoustic Transducer). Image processing technology for weld line detection at the surface of the target and host programs including defect detecting algorithms are also developed. Automation of defect detection for these kinds of large facilities using mobile robots is helpful to prevent significant troubles of the structures without danger of human beings under harmful environment.

• 한국음향학회지
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• 제9권3호
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• pp.24-30
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• 1990

본 연구에서는 표면에서 한파장 깊이 이내에 존재하는 결함 검출에 우수한 특성을 나타내는 meander line형 EMAT를 설계, 제작하고 그 특성을 연구분석하였다. 효율적인 동 자기장을 위하여 간격 0.72mm와 폭 0.65mm의 코일을 구성하였으며 정 자기장을 위하여 1500 가우스의 자석군을 구성하였다. 제작된 EMAT는 중심 주파수 2MHz, 비대역폭 36%를 가지며 임펄스응답 특성은 0.15 mm의 비접촉 방법으로 측정되어 이론과 비교되었고 중심 주파수에서의 삽입손실은 45.46 dB로 측정되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 춘계학술대회 논문집
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• pp.198-203
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• 1993

In this study, byusing EMAT(Electro Magnetic Acoustic Transducer) the artificial slit is installed on 12B-SUS pipe test piece. By mading 4 cycle SH-bust wave (EMA) incidence to 45 .deg. angle, the signaldata of pulse, which is recevied from EMAT translated intodigital-signal-processing-method SSP and Deconvolution method by using FACOM. Results of these indicated that (1) this method of this study shows exellent result more than Ultrasonic testing method; (2) noise is well removed by SSP using signal dataa and resolving power and S/N ratio are advanced; (3) regradless of Ultrasonic wave, whichhas properties of generalstainless steel is generated into multiscattering and reflection phenomena, the resolving power of more than two times is progressed by being translated into Decon-volution method; and (4) as addition-averaging-processing number is increaing, the resolving power and S/N ratio are improved and the satisfactory signal is obtained.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.194-196
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• 2005

Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of thinning defects simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided plate waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of thinning defects. Measurement of the mode group velocity can be also used to quantify of thinning depth.

• 비파괴검사학회지
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• 제22권3호
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• pp.254-260
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• 2002

화력발전소 보일러 튜브 및 대형 유체수송관의 자동 진단을 위해 비파괴검사 방법을 사용하는 두 가지 형태의 이동로봇을 개발하였다. 개발된 이동로봇은 보일러 튜브 또는 유체수송관의 외면을 주행하면서 전자기 초음파 탐촉자를 이용하여 파이프 벽면에 발생하는 미세한 구멍, 균열 또는 부식 및 침식에 의한 감육 등과 같은 결함을 검출한다. 이와 같은 이동로봇을 이용한 결합 검출의 자동화는 열악한 환경에서 작업자의 위험 없이 대형 구조물의 중대한 결함을 방지하는 유용한 수단으로 활용될 수 있다.

• 비파괴검사학회지
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• 제25권4호
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• pp.287-293
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• 2005

유도초음파는 박판이나 봉재와 같은 구조를 효율적으로 검사할 수 있는 초음파로 주목받고 있으며, 더불어 시험체를 비접촉으로 검사할 수 있는 기법이 개발되면서 다양한 분야에 응용하기 위해 연구되고 있다. 본 연구에서는 비접촉식 초음파기법과 유도초음파의 장점을 결합하여 기존의 검사기법에 비해 효율적인 검사기법을 제안하고자 하였으며, 실험적인 검증을 위해 알루미늄 박판에 모의 부식결함을 가공하여 두께감육을 검출하고 평가하였다. 제안된 비접촉식 초음파기법으로는 EMAT을 이용하여 유도초음파를 발생 및 수신하였다. 선택된 유도초음파 모드의 분산거동특성에서 모드 컷-오프는 두께 감육을 검출할 수 있는 정성적인 파라미터이며, 군속도 변화는 두께 감육의 깊이를 정량적으로 평가할 수 있는 파라미터로 나타났다.