Tone-Burst Generation of Circumferential Guided Waves by a Bulk Shear Wave Sensor and Their Wide-Range Time–Frequency Analyses

Abstract

Wide range generation of the circumferential guided waves (C-GWs) propagating along the perimeter of a pipe has been carried out using a single shear wave sensor along with several tone-burst sources. The C-GWs are classified mainly into two propagation modes, circumferential shear horizontal (C-SH) and circumferential Lamb (C-Lamb) waves. The authors previously reported that a simple and selective generation of the two modes using a single shear wave sensor could be realized by changing the polarization direction of the sensor. When the polarization direction of the sensor is parallel or vertical to the axial direction of a pipe, either the C-SH or the C-Lamb wave is selectively generated. In this paper, a newly exploited signal processing method to obtain a wide-range time–frequency analysis for the C-GW is proposed using wavelet transformation along with various tone-burst signals swept in the required frequency range. Time–frequency analyses of the results for the C-SH and C-Lamb waves propagating along 30-mm outer diameter and 1-mm-thick aluminum pipe are shown in comparison with the theoretical dispersion relation of the propagation modes. Quantitative evaluations of this method are discussed based on the Reciprocity theorem and Fourier transformation.