Defect detection in thin plates using So Lamb wave scanning

Francisco De Villa; Enrique Roldan; Cesar Tirado; Rodrigo Mares; Soheil Nazarian; Roberto A. Osegueda

doi:10.1117/12.434166

24 July 2001 Defect detection in thin plates using S_o Lamb wave scanning

Francisco De Villa, Enrique Roldan, Cesar Tirado, Rodrigo Mares, Soheil Nazarian, Roberto A. Osegueda

Proceedings Volume 4335, Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring; (2001) https://doi.org/10.1117/12.434166
Event: 6th Annual International Symposium on NDE for Health Monitoring and Diagnostics, 2001, Newport Beach, CA, United States

Abstract

This paper describes work towards the development of a Lamb wave scanning method for the detection of defects in thin plates. The approach requires the generation of an ultrasonic S₀-Mode Lamb wave using an incident transmitter excited with a tone burst centered at a near non-dispersive frequency. A pair of receiving transducers, with a fixed relative separation, remotely scans line sections of the thin plate. The global position of the receiver pair is moved to cover a large plate area. The arrival time information coming from incident and reflected waves contain information associated with the location of reflection surfaces or potential flaws. The cross-correlation between the excitation signal and the receivers' waveforms is obtained and subsequently demodulated using a quadrature amplitude method in order to facilitate the determination of arrival times. Distances from the source, to the reflection surface and to the receivers are found from the arrival times of the reflected waves and the Lamb wave phase velocity. The distances and the source and receiver locations are incorporated in an elliptical solution to find coordinates of the reflection points. In a line scanning the set of predicted reflection points define the extent of the defect. The Lamb wave scanning approach is tested using 1.6 mm-thick Aluminum plates with notches of various lengths and orientations from 0, 22.5 and 45 degrees with respect to the far edge of the plates. The results are summarized with defect maps that compare favorably to the actual notch locations.

Citation Download Citation

Francisco De Villa, Enrique Roldan, Cesar Tirado, Rodrigo Mares, Soheil Nazarian, and Roberto A. Osegueda "Defect detection in thin plates using S_o Lamb wave scanning", Proc. SPIE 4335, Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring, (24 July 2001); https://doi.org/10.1117/12.434166

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