Best Reconstruction Frequency of Lamb Waves Via Broadband Measurement

Abstract

This article presents the theoretical basis of the best reconstruction frequency (BRF) of Lamb waves. It has been proposed earlier by the author’s group as the probing frequency in the refined time-reversal method for damage detection to achieve enhanced sensitivity and accuracy. It is shown to be the frequency at which the amplitude dispersion of the main mode of the reconstructed signal is minimum. It is then possible to compute the BRF from a single measurement of Lamb wave response under a broadband (e.g., Gaussian) excitation. Thus, it is no longer required to compute the similarity at different central frequencies of the narrowband input. It is further shown that the BRF is a system property of a given transducer-plate-adhesive system, which is independent of the distance between the transducers used for the time-reversal method in pitch-catch mode. This property makes it suitable for use when a network of sensing paths is used to identify damage locations.