Optimum excitation signal for long-range inspection of steel wires by longitudinal waves

Optimization of an excitation signal is proposed for long-range inspection of thin steel wires by ultrasonic waves. Due to its sensitivity to flaws normal to the axial direction, a longitudinal wave is a useful tool for flaw detection of wires. We can launch and detect longitudinal waves at arbitrary positions on the wire by using electromagnetic acoustic transducers. The broadband pulse is suitable for achieving high spatial resolution in locating flaws. However, the dispersion of the longitudinal wave distorts the waveform, and consequently decreases the apparent signal amplitude. If the effect of the dispersion is removed, the signal to noise ratio can be expected to be improved and the high flaw detectability can be obtained. In this study, we suggest using the optimum excitation signal, which has been modified to compensate for the dispersion during the propagation of the assumed path length. It is possible that the flaw, which occupies 10% of the cross-sectional area of the wire, can easily be detected from a distance of 10 m. (C) 2001 Elsevier Science Ltd. All rights reserved.