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Dr. Manyong Choi

Study on fabricating Micro-crack specimen and applying Variable-Frequency Ultrasound Infrared Thermography


Dr. Manyong Choi

Non-Destructive Testing (NDT) market in nuclear power industry has currently great marketability approximately of 200 billion won and 1,200 trillion won per year in domestic and world market, respectively. Radiographic Test (RT) is normally used to examine nuclear power plants before its installation and Ultrasonic Test (UT) is after its operation. It is important to detect micro-cracks occurring in the initial stage, which can cause a catastrophic problem in nuclear power plant. However, defects in cast austenite stainless pipes is difficult to detect since RT takes long time and UT may require complex signal analysis. This study sought to develop technologies 1) to fabricate thermal fatigue and stress corrosion cracks in a casting pipe by controlling the defect size, and 2) to detect the defects using the variable-frequency ultrasound infrared thermography. As a result, the thermal fatigue and stress corrosion cracks with a depth of 50% were fabricated, which are located in the pipe with 5 inches in external diameter and 0.5 inches in thickness, and a system was developed, which can detect the fabricated defects .