Generation of Circumferential Guided Waves Using a Bulk Shear Wave Sensor and their Mode Identification

A novel method of generating circumferential guided waves (C-GWs) propagating in a pipe has been proposed using a single bulk shear wave (BSW) sensor. The generated C-GWs are classified into circumferential shear horizontal (C-SH) waves and circumferential Lamb (C-Lamb) waves. The BSW sensor is dry-coupled on the outer surface of the pipe to generate the C-GWs. The selective generation of the C-SH wave or the C-Lamb wave was realized by changing the polarization direction of the BSW sensor relative to the axial direction of the pipe. The C-SH and C-Lamb waves were selectively generated using a 66-mm-outer-diameter and 0.1-mm-thick steel pipe, and a 30-mm-outer-diameter and a 1-mm-thick aluminum (Al) pipe, respectively. The obtained results were compared with both theoretical group velocities and particle displacements to identify the specific propagation mode. The group velocities of the generated C-GWs were in good agreement with the theoretical values. The generation efficiency of the C-GWs was also discussed on the basis of the theoretical particle displacements for their modes.

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