• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.177-184
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• 2012

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 1995.12a
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• pp.17.1-17
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• 1995

• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.245-255
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• 2001

원전 가동전/가동중검사 결과의 신뢰도(reliability)는 원전 배관기기의 건전성에 직결되는 것으로써 결함 발견 시 적용되는 파괴역학해석(FMA)은 비파괴검사 결과에 대한 100%의 신뢰를 전제하고 있다. 그러나 비파괴검사가 어느 정도 신뢰성을 가지고 있는지에 대한 평가가 국내에서는 거의 수행된 바가 없었다. 따라서, 본 연구에서는 원전의 비파괴검사 규제 요건의 기술적 근거를 확보하고, 원전 기기 건전성 평가 및 안전성 향상을 위한 합리적 규제지침을 수립하기 위하여 국내 원전 가동중검사(ISI)에 적용되거나 일반 산업계에 적용되고 있는 초음파탐상검사에 대하여 기량검증 Round Robin Test에 의한 통계적 신뢰도를 평가하고자 한다. 이를 위해 초음파검사 PD-RRT 결과의 통계적 신뢰도 평가 모델을 고찰하고, 결함검출성능 평가, 결함크기 측정 평가, 팀 오차 분석 등 초음파검사 PD-RRT 결과의 통계적 신뢰도를 평가하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.1
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• pp.38-43
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• 1991

The relationship between eddy current response and case hardening depth has been studied on SM40C(KS D-3752) and SCM440(KS D-3711) steels which were surface hardened by high frequency induction hardening. The results obtained in this study were as follows ; 1) Case hardening depth was successfully measured by observing the eddy current impedance changes of each steel. The impedance decreased linearly with increasing case hardening depth. 2) For large impedance gradient between the hardened surface and core metal, the eddy current response was more sensitive to case hardening depth than for low impedance gradient.

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.531-538
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• 1999

비파괴 품질 평가 기술인 핵 자기공명 분광법과 자기공명영상을 이용하여 소고기의 내부 구조를 분석하였다. 이완 상수 T$_1$과 T$_2$가 육류의 내부 구조와 관계가 있음을 보였다. 근육부분의 면적 비율이 증가할수록 T$_1$이 증가했다. 지방 부분의 T$_2$는 배 내부 부분의 T$_2$와 비슷한 값을 보였다. 자기공명 영상을 이용하여 육류의 원하는 부위의 T$_2$를 측정할 수 있는 방법을 구하였다. 근육 부분의 T$_2$가 길었으며 지방 부분의T$_2$가 짧았다. 부위별로 최적의 신호를 얻을 수 있는 자기공명영상 인자 TR과 TE를 구하였다. 자기공명영상을 이용하여 근육, 지방 그리고 뼈 성분에 따른 육류의 품질을 비파괴적으로 평가할 수 있는 가능성을 보여주었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.65-72
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• 2000

콘크리트 구조물이 지진 등으로 손상을 입었을 때 그 내부 상태를 파악하는 일은 구조물의 안전성 판단에 필요한 중요 과정중 하나이다 손상도 파악에 사용되는 비파괴 검사 방법 중 레이더법은 현재 콘크리트 부재의 두께와 매립된 철근 및 공동 탐사에 적용되고 있다 레이더법은 다른 비파괴 검사 방법에서와 마찬가지로 측정된 신호의 처리와 해석에 따라 그 결과가 좌우된다 . 이논문에서는 상용 레이더 시스템에서 얻어지는 화상 데이트터를 개선하는 방법을 개발하여 철근이 매립된 콘크리트 시편에 적용하였다 실험에 사용된 기편의 크기는 1,000mm(길이)$\times$600mm (폭) $\times$140mm(두께) 이고 철근의 매립깊이는 표면으로부터 철근 중심까지 60mm 이다 레이더 실측 실험에서 철근의 수평배근 간격을 60 90, 120, 150 mm 로 변화시켜 간격탐사가능성을 시험하였다 결과적으로 상용 시스템에 비해 샹상된 판별효과를 나타냈으며 배근 간격이 90, 120, 150mm 인 시편에서 그 간격을 정확히 찾아내었다.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.2
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• pp.112-120
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• 1998

A nondestructive evaluation technique was developed for the quantitative determination of the reinforcement volume fractions in particulate reinforced metal matrix composites. The proposed technique employed a composite micromechanics which accounts for the microstructure of the composite medium together with the measurement of anisotropic electrical conductivity. When the measured conductivity was coupled with the theoretically predicted conductivity, the unknown reinforcement volume fraction was calculated. An analytical model based on the Mori-Tanaka method was described which relates the NDE signatures to the composite microstructure. The volume fractions were calculated using eddy current measurements made on a wide range of silicon carbide particulate ($SiC_p$) reinforced aluminum (Al) matrix composites. The calculated $SiC_p$ volume fractions were in good agreement with the measured volume fractions in the range of 0-30%. The technique was also found to be effective in estimating the total volume percentage of reinforcement and intermetallic compound formed during the processing stage.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.192-197
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• 2012

In this paper, a non-contact microwave technique was presented to detect the surface crack of the metals. An open-ended coaxial cable line was used as a sensor at 11 GHz, and the reflection coefficients were measured by scanning along the metal surface including artificial surface cracks. A parameter, the K value which was defined as the difference between maximum and minimum reflection coefficients, was measured and used to estimate the crack depth. A linear relationship between the K value and crack depth was found. This study showed that non-contact detection of the surface cracks of metals is possible using the open-ended coaxial line sensor at X-band.

• Journal of Conservation Science
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• v.26 no.1
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• pp.77-83
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• 2010

The damage from the underground termite cannot be discovered with peculiar appearance of building but hollow phenomenon will occur. But there is no case in Korea as a non-destructive measurement of termite activation. Therefore, this research constructs non-destructive diagnostic techniques for wooden cultural properties using microwave detector (Termatrac, Australia). Result of maximun distance were measured 16cm (Pine tree, sensitivity 5, 6), 17cm (Zelkova and Douglas fir, sensitivity 5, 6). These results are expected that can be applied in the field. Result of field test using microwave detector, 33.8% of the wooden cultural properties were damaged by termites, and until now 7.8% (18 buildings) are being damaged in nationwide (total 231 buildings). Based on the above results, microwave detector will be able to be utilized effectively for detecting termite, preventing intrusion in wooden structure, and making full use of monitoring system periodically. In addition, it could be of great worth in preventing insect and microorganism in wooden structure.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.164-176
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• 2008

In order to assess the existing infrastructures, it is required to measure the crack depth of concrete members. This paper considers the surface wave transmission technique to measure the crack depth. In special, we demonstrate the effect of reinforced bar on surface wave propagation and conclude that the surface wave transmission technique has only the minor error by the reinforced bar. In addition, we propose and validate the optimal window size for eliminating various reflection waves from the boundary of members.