Waveform Distortion of Longitudinal Wave in Wire by Velocity Dispersion

• Published in: Transactions of the Japan Society of Mechanical Engineers Series A Vol. 65; no. 636; pp. 1728 - 1733
• Main Authors: YAMASAKI, Tomohiro, TAMAI, Shingo, HIRAO, Masahiko
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society of Mechanical Engineers 1999
• Subjects: Dispersion; Electromagnetic Acoustic Transducer; Fast Fourier Transform; Iron and Steel; Ultrasonic Inspection; Wire
• ISSN: 0387-5008; 1884-8338
• DOI: 10.1299/kikaia.65.1728

Waveform distortion induced by velocity dispersion is simulated for longitudinal wave, which propagates along the length of a thin wire. In inspection of a thin wire throughout a long range, the longitudinal wave is useful, while the velocity shows the frequency dependence. In the conventional flaw detection by ultrasonics, short pulse is used as an excitation signal because of the high resolution of flew location. As a result of the velocity dispersion. the waveform is distorted, which causes the spread of the pulse width and the decrease in the signal amplitude. The signal to noise ratio will then be reduced. In this study, we simulate the waveform by giving the phase delay to each frequency component using the theoretically calculated dispersion curve. Comparing the simulated amplitude with the experimental results, we find that the signal amplitude is mainly decreased by the velocity dispersion and that the effect of the attenuation can be neglected even for 30 m propagation as long as pulse of low frequency range is used.