Papers by Author: Seung Han Yang

Abstract:
The results of ultrasonic testing performed during in-service inspection period for main components of nuclear power plant are affected by the performance of each inspector. To enhance the inspection reliability, the more restrictive qualification is required. KEPRI established Korean performance demonstration (KPD) system for the ultrasonic testing personnel, equipment and procedure which applied to the piping examination of nuclear power plant. A round robin test was conducted to evaluate the reliability of examination result by comparing conventional (DAC) UT and performance demonstration (PD) UT method. Participants took detection/length sizing test and depth sizing test using DAC method and PD method. The results showed that the PD method was preciser and more accurate than the conventional DAC method in length and depth sizing regardless of field experience and PD qualification status.

Abstract: This paper presents a non-destructive evaluation (NDE) technique for detecting damages on a jointed steel plate on the basis of the time of flight and wavelet coefficient, obtained from wavelet transforms of Lamb wave signals. Probabilistic neural networks (PNNs) and support vector machines (SVMs) were applied for pattern classification. In this study, the applicability of the PNNs and SVMs was investigated for the damages in and out of the Lamb wave path. It has been found that the present methods are very efficient in detecting the damages simulated by the loose bolts on the jointed steel plate.