J041045 円周Lamb波による自己干渉性を利用した配管肉厚測定法における周波数特性の校正による高精度化([J041-04]超音波計測・解析法の新展開(4))

抄録

In this paper, a method of accurately measuring the pipe wall thickness by using noncontact air-coupled ultrasonic transducer (NAUT) was presented. In this method, accurate measurement of angular wave number (AWN) is a key technique because the AWN is changes minutely with the wall thickness. An autointerference of the circumferential (C-) Lamb wave was used for accurate measurements of the AWN. Principle of the method was first explained. Modified method for measuring the wall thickness near a butt weld line was also proposed and its accuracy was evaluated within 6 μm error. It was also shown in the paper that wall thickness measurement was accurately carried out beyond the difference among the sensors by calibrating the frequency response of the sensors.