Time-of-Flight Extraction Method for the Electromagnetic Ultrasonic Guided Wave Detection Signal

Given the multimode and dispersion characteristics of an electromagnetic guided wave, guided wave modal research and control are mainly conducted from two aspects of work mode or work point selection and guided wave detection signal processing. When the ultrasonic guided wave is in the multimodal working mode, various modal guided waves are propagated in the steel plate according to the pre-set working point and are converted into voltage signals by receiving EMAT through the role of defects, and are amplified, filtered, and the guided wave detection data are formed after the acquisition and processing. The guided wave detection data exist in the form of signal wave packets in the time domain. The guided wave detection signals of various modes are aliased in the same wave packet in the time domain and cannot be directly analyzed and processed in the time domain. It is necessary to separate the modal guided wave detection signals in the time domain wave packet to identify the corresponding modal guided wave in the guided wave detection signal, to make a clear and reasonable explanation for the guided wave detection signal.