Ultrasonic guided wave phased array based on reconstructed pulse-echo signals from phase information

Abstract

Abstract Aiming at the inherent dispersion characteristics of ultrasonic guided waves and the problems of gratings and side lobes in classical total focusing method (TFM) imaging algorithms, this paper proposes a full focus imaging algorithm based on reconstruct signals from phase information. Utilizing the numerical solution of the dispersion curve in the wavenumber domain, the time domain signal of Lamb wave is propagated backward to revise the changes in waveform shape caused by dispersion, and the flight time of the pulse-echo is eliminated simultaneously. The phase of pulse-echo after dispersion compensation should be consistent with the excitation signal. And the pulse-echo should have a large waveform correlation coefficient with the excitation signal. For each imaging point, dispersion compensation for all collected signals is respectively implemented so that the sign coherence factor (SCF) and the waveform correlation factor (WCF) between pulse-echo and excitation waveform can be extracted to reconstruct scattering signals. The reconstructed signals only contain information about the pulse-echo from defect. TFM imaging of the reconstructed signal can effectively suppress the grating side lobes of classical TFM imaging and improve the signal-to-noise ratio (SNR).