Classification of Ultrasonic Flaw Signals by Means of Time-Frequency Analysis (2nd Report, Flaw Signals Classification by Single Ultrasonic Probe)

摘要

The previous classification method(1) which is based on a time-frequency analysis, can classify three types of artificial flaws, side-drilled hole, flat-bottomed hole and slit. But this method requires two ultrasonic probes to distinguish these flaws. As this method is complicated, this paper examines the phase of flaw signal to develop a single ultrasonic probe method. The phase value of flaw signal is analyzed by STFT, a method of time-frequency analysis. As a result of analysis, it is clear that narrow slit causes a change of the phase value and there is a difference in the phase value between the side-drilled hole and the slit. In the previous method, the flat-bottomed hole can be distinguished from both the side-drilled hole and the slit by a probe of 6 mm aperture diameter. Therefore, by combining the previous and the present methods, a single ultrasonic probe method which can classify three types of artificial flaws is achieved.