Attenuation Analysis of Lamb Waves Using the Chirplet Transform
1 Institute of Mathematics and Computing Science, University of Groningen, 9700 AV Groningen, The Netherlands
2 Institute of Applied and Experimental Mechanics, University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
3 Computer Science Department, University of North Carolina, Chapel Hill, NC 27599-3175, USA
4 School of Civil and Environmental Engineering and G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
EURASIP Journal on Advances in Signal Processing 2010, 2010:375171 doi:10.1155/2010/375171Published: 14 June 2010
Guided Lamb waves are commonly used in nondestructive evaluation to monitor plate-like structures or to characterize properties of composite or layered materials. However, the dispersive propagation and multimode excitability of Lamb waves complicate their analysis. Advanced signal processing techniques are therefore required to resolve both the time and frequency content of the time-domain wave signals. The chirplet transform (CT) has been introduced as a generalized time-frequency representation (TFR) incorporating more flexibility to adjust the window function to the group delay of the signal when compared to the more classical short-time Fourier transform (STFT). Exploiting this additional degree of freedom, this paper applies an adaptive algorithm based on the CT to calculate mode displacement ratios and attenuation of Lamb waves in elastic plate structures. The CT-based algorithm has a clear performance advantage when calculating mode displacement ratios and attenuation for numerically-simulated Lamb wave signals. For experimental data, the CT retains an advantage over the STFT although measurement noise and parameter uncertainties lead to larger overall deviations from the theoretically expected solutions.