Mathematical Problems in Engineering
Volume 2012 (2012), Article ID 358128, 15 pages
Research Article

Warped Wigner-Hough Transform for Defect Reflection Enhancement in Ultrasonic Guided Wave Monitoring

1Department of Electronics, Information and Computer Systems (DEIS), University of Bologna, 40136 Bologna, Italy
2Department of Civil, Environmental and Materials Engineering (DICAM), University of Bologna, 40136 Bologna, Italy

Received 27 August 2012; Revised 19 October 2012; Accepted 20 October 2012

Academic Editor: Zhongqing Su

Copyright © 2012 Luca De Marchi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


To improve the defect detectability of Lamb wave inspection systems, the application of nonlinear signal processing was investigated. The approach is based on a Warped Frequency Transform (WFT) to compensate the dispersive behavior of ultrasonic guided waves, followed by a Wigner-Ville time-frequency analysis and the Hough Transform to further improve localization accuracy. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested by analyzing numerically simulated Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented for real-world structural health monitoring applications.