Excitation of torsional guided waves with flexible PZT transducers in water-filled pipes

Abstract

Estimation of structural damage to predict the service lifetime of liquid-filled pipelines is important to reduce waste or to avoid accidents. In this work, experimental and numerical simulations were carried out to characterize the acoustic wave propagation of the lowest cylindrical torsional mode in a pipe with discontinuities. Wave mode was generated and received using flexible macro-fiber composite transducers (MFC). An analysis of beam energy directionality of shear horizontal (SH) and Lamb modes was carried out prior to the tests on the cylindrical structure. A method to control the generation and detection of torsional waves in the pipe considering the directionality of the SH-plate waves was proposed. Tests were carried out in a water-filled pipe to study the leakage effect in the detection of discontinuities. The results showed that although torsional as well as flexural modes can be simultaneously excited by the MFC patch actuator, the orientation of the patch can also allow mode selection. Finally, it was found that flexible patches generate torsional waves efficiently and could be used to detect circumferential discontinuities in water-filled pipes.