Time reversal beamforming of guided waves in pipes with a single defect

Structural health monitoring of buried pipelines is an important application for aging infrastructures. Ultrasonic guided wave inspection is an attractive tool, due to the long propagation of guided waves in the wall of a hollow cylinder. However, guided waves present a unique environment with heavily multi-modal signal propagation and complex dispersion (frequency-dependent propagation speeds). In order to alleviate these challenges, conventional techniques rely on high-voltage excitation with complex transducer arrays, but these systems are not conducive to a monitoring solution. Instead, they require periodic excavation and testing. In prior work, we have shown that Time Reversal allows for reliable detection with relatively simple antenna arrays that can be operated in low-power. This paper focuses on localization of these defects. We utilize a beamforming approach that makes use of theoretical dispersion curves to generate fault images. We show through simulations that Time Reversal Beamforming achieves high-resolution localization of a fault in the presence of strong dispersion and heavily multi-modal propagation.