<p>The performance degradation of ferromagnetic materials generally occurs under a long-term working period in a high-temperature environment, affecting the service life and safety of equipment. Electromagnetic acoustic transducer (EMAT) has the advantages of non-contact detection based on electromagnetic induction. They can be used in the non-destructive testing and evaluation of equipments. However, only the ultrasonic wave of the EMAT testing signal is exploited, while other information of the EMAT testing signal is ignored. In this study, a theoretical analysis of the EMAT testing signal was conducted, and it was proposed that the EMAT testing signal for ferromagnetic materials included a pulsed eddy current, Lorentz force ultrasonic wave, and magnetostriction force ultrasonic wave. This opinion was proven based on both experiment and simulation studies. The reasonable signal decoupled and separated methods for the EMAT testing signals were proposed. The pulsed eddy current and ultrasonic waves could be decoupled in the frequency domain, and the ultrasonic waves could be separated in the time domain. The pulsed eddy current, Lorentz force ultrasonic wave, and magnetostriction force ultrasonic wave could be obtained through a single detection of an EMAT. The acoustic and magnetic parameters could be collected to characterize the performance degradation of ferromagnetic materials. The assessment accuracy of ferromagnetic materials performance degradation could be improved by a magneto-acoustic compounding inspection method. This could greatly improve the detection ability and the robustness of the electromagnetic acoustic testing of an EMAT.</p>

Analysis and Separation of Emat Testing Signal for Ferromagnetic Materials

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.