저면 반사파를 이용한 피로 균열의 정량적 평가에 관한 연구 = Quantitative Evaluation of Fatigue Cracks Using Reflected Signals from Back Wall

다국어 초록 (Multilingual Abstract)

Fatigue cracks due to thermal stratification or corrosion in pipelines of nuclear power plants can cause serious problems on reactor cooling system. Therefore, these cracks must be detected before the crack growth to ensure the reliable operation. Ultrasonic techniques have been employed for detecting and sizing these fatigue cracks propagated from the back wall of pipelines. But, it is very difficult to sizing fatigue cracks because of low amplitude of the diffracted tip signal, high noise signal and ultrasound transmission through the closed crack surface. In this study, the signal reflected from the back wall is adopted instead of weak tip signals. In addition, the rate of decrease in amplitude of reflected signals due to reflection at the crack surface and diffraction at the crack tip is used to size fatigue cracks.