Abstract:
To investigate the influence of signal choice on flaw detection,detection is done on single flaw by using 4 tone bursts with different cycles at 120 kHz in a 7.12 m long pipe.The tone burst of 20 cycles is suitable for flaw detection in the pipe by comparing and analyzing corresponding experimental results.When its cycle number becomes smaller,the tone burst is unsuitable to detect flaws because the waveform of excited
L(0,2)mode becomes narrower,and its frequency spectrums become wider,signal-to-noise ratio(SNR)of flaw signals become smaller,and the dispersion of converted modes,such as flexural modes,becomes more serious when the incident mode reflects from the flaw.When its cycle number gradually increases to a certain value,frequency spectrum of excited
L(0,2)mode becomes narrower,its dispersion becomes more inconspicuous,and the SNR of flaw signals become larger,thus,the tone burst with this number of cycles is suitable for flaw detection.However,the tone burst becomes improper when its cycle number increases largely.Because flaw echoes are inclined to superpose mutually when durations become longer.