Beamforming Imaging in Cylindrical Structures Using Helicoidal Reflected SH Waves

Abstract

Implementing guided wave imaging (GWI) for structural health monitoring (SHM) of cylindrical structures can be enhanced by simplifying the physics and utilizing all the information generated by wave interactions with the mechanical guide and discontinuities. A beamforming method for SH0 waves reflected from a trough-hole in a cylinder has been developed. This method considers the mode conversion from T(0,1) to SH0 waves, which follow direct and helical paths before converting back to torsional waves. The use of helical paths enables the deployment of an array of sensors distributed along a section of the cylinder’s circumference. Indeed, signal identification and integration into a beamforming scheme present challenges due to the multiple trajectories that prop- agate around the cylinder. The objectives of the numerical analysis are threefold: first, to model the propagation and interaction of torsional waves with a discontinuity; second, to numerically identify the helicoidal wave trajectories for full rotations (orders); and third, to develop and implement a frequency-domain MUSIC beamforming algorithm adapted for cylindrical structures. The results demonstrate the ability to reconstruct the defect’s position and orientation. These findings highlight the potential of the proposed method for accurate defect localization in cylindrical structures.