Mode separation and characterization of torsional guided wave signals reflected from defects using chirplet transform

The sensor configuration of a magnetostrictive guided-wave system can be described as a single continuous transducing element which makes it difficult to separate the individual modes from the reflected signal. In this work, we develop the mode decomposition technique employing chirplet transform, which is able to separate the individual modes from dispersive and multimodal waveforms measured using the magnetostrictive sensor, and estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize defects. The reflection coefficients are calculated using the modal energies of the separated modes. Experimental results on a carbon steel pipe are presented, which show that the accurate and quantitative defect characterization could be enabled using the proposed technique.