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정용무 韓國非破壞檢査學會 1988 한국비파괴검사학회지 Vol.7 No.2
Interfaces, both grain boundaries and phase boundaries, play a very important role in the mechanical behavior of structural materials. The problems particularly intense in composite materials where interfaces play a primary role in the mechanical response of the composites. This paper will concentrate on the approaches to perform nondestructive evaluation of the interfaces in a manner in which some measure of the mechanical behavior of the interface can be established. Some of the possible approaches that may potential for the nondestructive evaluation of interfaces are optical, electronic/electrical, and acoustic approaches.
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정용무 한국비파괴검사학회 1991 한국비파괴검사학회지 Vol.11 No.1
The multi-frequency eddy current technique has been used for evaluation of various type of defects in tubings. However, this technique is not sufficient to detect and evaluate the defect in tubings if the defect is located in the geometrically complicated area(e. g. tube support plate, anti-vibration bar, tubesheet area) and mixing residue signal is significant to the defect signal. In order to improve the reliability of the multi-frequency eddy current technique, the effect of the interaction of mixing residue after frequency mixing with a function of distances between the defect and the tube support plate boundary has been analyzed theoretically. The experimental results have been discussed with the theoretical developments. The calculation shows the interaction between the two neighboring signal sources could be significant within the range of approximately 1.0mm with the experimental condition.
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정용무 한국비파괴검사학회 1991 한국비파괴검사학회지 Vol.11 No.2
The integral model for the eddy current phenomena has been suggested. The model could lift the limitations of the previously well-known analytical model of eddy current theory. The model could be applied to two-dimentional, arbitary shaped defects. The computer programs have been developed in oder to calculate the eddy current signal with the suggested integral method. The eddy current signals by the model calculations have been shown similar patterns to the actual experimental data from the real defects in the calibration standard tubes.
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중수로 핵연료채널과 인접관의 간격측정을 위한 원거리장 와전류검사 기술개발
정현규,이동훈,이윤상,허형,정용무 한국비파괴검사학회 2004 한국비파괴검사학회지 Vol.24 No.2
중수로 내부구조물 중 칼란드리아관(CT)와 액체주입노즐관(LIN)은 서로 수평으로 90도 교차되게 배열되어 있으며 원자로 내의 열, 방사선, 하중에 의해 creep 현상이 발생되어 처짐이 일어난다. 칼란드리아관은 액체주입노즐관과 동일 재료이나 운전 온도와 방사선 조사량으로 인해 액체주입노즐에 비해 상당히 열악한 조건에 노출되어 있으므로 처짐이 심각할 것으로 예상된다. 만약 두 관의 접촉이 발생되면 원전 안전성에 영향을 미칠 것이므로 인접관에 대한 접촉여부 점검은 중수로 안전현안 중 하나이다. 이러한 접촉여부를 확인하기 위하여 핵연료채널 내부로 탐촉자를 삽입하여 인접관과의 교차점에서 간격을 직접측정하기 위한 방법으로 원거리장 와전류검사(RFECT) 기술을 적용하였다. 핵연료채널 인접관인 액체주입노즐관 신호 취득시 발생 가능한 잡음 신호(두께변화, Lift-off, 수축)에 대해 체적적분법에 의한 모델링으로 조사하였고, 신호와 잡음과의 분리가능한 조건을 확인하였다. 원거리장 와전류검사 적정 조건은 민감도와 투과력 그리고 잡음신호 등을 동시에 고려하여 주파수 1kHz와 코일간격 200mm로서 결정하였다. 원거리장 와전류검사 실험 결과 칼란드리아관과 액체주입노즐관 사이의 간격 변화에 대한 신호 특성을 전압평면을 이용하여 상관관계를 도출하였다. Liquid Injection Nozzle(LIN) tube and Calandria tube(CT) in Pressurized Heavy Water Reactor (PHWR) are cross-aligned horizontally. These neighboring tubes can contact each other due to the sag of the calandria tube resulting from the irradiation creep and thermal creep, and fuel load, etc. In order to judge the contact which might be the safety concern, the remote field eddy current (RFEC) technology is applied for the gap measurement in this paper LIN can be detected by inserting the RFEC probe into pressure tube (PT) at the crossing point directly. To obtain the optimal conditions of the RFEC inspection, the sensitivity, penetration and noise signals are considered simultaneously. The optimal frequency and coil spacing are 1 ㎑ and 200 ㎜ respectively. Possible noises during LIN signal acquisition are caused by lift-off, PT thickness variation, and gap variation between PT and CT. The simulated noise signals were investigated by the Volume Integral Method(VIM). Signal analysis on the voltage plane describes the amplitude and shape of LIN and possible defects at several frequencies. All the RFEC measurements in the laboratory were done in variance with the CT/LIN gap and showed the relationship between the LIN gap and the signal parameters by analyzing the voltage plane signals.
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교차 배열된 지르코늄관 간격 측정을 위한 전압 평면에서의 신호해석
정현규,이윤상,이동훈,허형,정용무 한국비파괴검사학회 2003 학술대회 논문집 Vol.- No.1
The eddy current(EC) signals were evaluated for gap measurement of cross aligned zirconium tubes for preventing the contact which might be the safety concern. Liquid lnjection Nozzle(LIN) tube and Calandria tube(CT) were cross-aligned horizontally and LIN could be detected by inserting the EC probe into pressure tube (PT). Signal analysis on the voltage plane was applied to describe the position and shape of possible defects using several frequencies. Test variables are lift-off, PT thickness variation, and gap variation between PT and CT All the EC measurements in the laboratory were done in variance with the gap spacings and showed the possibility to evaluate the gap between CT. and LIN tube by analyzing the signal on voltage plane. Electromagnetic technique could be a potential tool for inspecting the inter-tube gap in CANDU reactor.
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