Array-Based Guided Wave Source Location Using Dispersion Compensation

Abstract

An important advantage of guided waves is their ability to propagate large distances and yield more information about flaws than bulk waves. Unfortunately, the multi-modal, dispersive nature of guided waves makes them difficult to use for locating flaws. In this work, we present a method and experimental data for removing the deleterious effects of multi-mode dispersion allowing for source localization at frequencies comparable to those of bulk waves. Time domain signals are obtained using a novel 64-element phased array and processed to extract wave-number, and frequency spectra. By an application of Auld's reciprocity theorem, mode amplitudes are extracted approximately using a variational method. Once mode contributions have been obtained, the dispersion for each mode can be removed via back-propagation techniques. Excepting the presence of a small artifact at high frequency-thickness products, experimental data successfully demonstrates the robustness and viability of this approach to guided wave source location.

Split-Spectrum Processing with Raised Cosine Filters of Constant Frequency-to-Bandwidth Ratio for L(0,2) Ultrasonic Guided Wave Testing in a Pipeline

“…Dispersion compensation (DC) is another signal processing method commonly applied in UGW testing, where the coherent noise can be eliminated by reversing the effect of dispersion and multi-mode on the desired mode UGW in the time/space domain [13]. Downs et al [14] obtained UGW signals through an original 64-element phased array, extracted wavenumber and spectrum analysis coherent noise, used Auld's electromechanical reciprocity relationship and variational method to extract mode contributions and finally used a dispersion compensation method to eliminate the coherent noise. On the basis of DC, Luo et al [15] proposed two wideband Lamb wave time-frequency dispersion analysis methods: time-frequency compensation transform and time-frequency de-dispersion transform, and the results show that both methods can obtain high-resolution Lamb wave signals.…”