誘導超音波技術을 利用한 細管의 缺陷測定에 관한 硏究

다국어 초록 (Multilingual Abstract)

As a part of the measuring system, like a nervous system in human body, a mass of small tubes are installed in Nuclear Power Plants, an involved tubing system. Each of the tube is mostly less 1 inch in diameter, and extends over about 40m in total length. A visual inspection method has been mainly taken for the testing of integrity on the tubing system. However, it is a time-consuming method demanding lots of inspectors as well as extremely weak on radiation protection.
Therefore, in an effort to find an alternative method, this study was undertaken aiming to test if guided wave technology is available in examining DN tubing of 3/8inch in Diameter installed in PHWRs.
The guided wave method has never been used for the examination of 3/8inch tubing yet all over the world. In this study, DN tubing mockups with circumferential and axial direction cracks made by electrical discharge Machining(EDM) have been examined.
During the study, the optimum frequency was set with analysis of S/N rate as per the variation of test frequency, and the signal sensitivity to the defect size and orientation was also interpreted in each frequency.

Major findings of this study are summarized as follows
1. From the experimental results related to the S/N rate in 3/8inch tubing, the optimum frequency is observed at 100kHz.

2. The optimum frequency for axial flaws is observed at 100kHz.

3. Except for the 20% circumferential flaw, the optimum frequency for circumferential flaws is observed at 100kHz.

4. It was possible to approximately make a quantitative analysis for the detection of the defect and defect size at 100kHz.

목차 (Table of Contents)

• 1. 서론 1
• 1.1 연구배경 1
• 1.2 연구 목적 1
• 2. 이론적 고찰 2
• 2.1 검사자료 검토 2
• 2.2 유도초음파 5
• 2.3 유도초음파 분산성 7
• 2.4 원통에서의 유도초음파 모드 특성 8
• 2.5 유도초음파 파형구조 11
• 2.6 주파수 레짐 15
• 2.7 유도초음파 파동형태(waveform) 15
• 3. 시편설계 및 실험방법 19
• 3.1 시편설계 및 제작 19
• 3.2 실험장치 구성 및 실험 방법 21
• 3.2.1 탐촉자 21
• 3.2.2 펄서/리시버 21
• 3.2.3 검사시스템 23
• 3.2.4 실험방법 24
• 3.3 신호 수집 및 평가 24
• 3.3.1 신호수집 24
• 3.3.2 신호평가 27
• 4. 실험결과 및 고찰 30
• 4.1 주파수 변화에 따른 노이즈 영향 평가 30
• 4.2 결함방향에 따른 신호 감도 분석 34
• 4.2.1 축 방향 인공결함 크기별 신호감도 분석 34
• 4.2.2 반경 방향 인공결함 크기별 신호감도 분석 37
• 4.2.3 축 방향 및 반경방향의 결함에 대한 신호감도 상호비38
• 5. 결론 41
• References 43
• Abstract 45