時間-周波数解析による超音波欠陥信号の弁別

概要

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An ultrasonic method for flaw type determination is described. Clearly, the lower the frequency of an ultrasonic longitudinal wave becomes, the wider the beam spreads. In the case of a large flaw, there is a difference in the beam path between low and high frequency components. Therefore, the propagation time of a low frequency component is longer than that of a high frequency component. On the other hand, in the case of a small flaw, there is little difference in the propagation time between the components. Hence it is possible to determine the flaw type, by analyzing the propagation time of a particular frequency range. Time-frequency, t-f, analysis is applied to the ultrasonic signals reflected by three types of artificial flaws; side drilled holes, fiat-bottomed holes and slits. The Short Time Fourier Transform, STFT, method of t-f analysis is found to be effective. The results support the feasibility of classification of flaws by means of t-f analysis of the reflection of ultrasonic waves emitted by probes of different diameter.
一般社団法人日本機械学会の論文
1997-05-25