Performance Analysis of High-Temperature Flexible Dual-Coil EMAT for Ferromagnetic Steel Measurement

The electromagnetic acoustic transducer (EMAT), which uses a flexible dual-coil configuration, can be easily applied for noncontact ultrasonic testing of curved structures and objects with narrow inspection space. In this article, the high-temperature performance of a flexible dual-coil EMAT on ferromagnetic steel measurement is analyzed. The flexible dual-coil EMAT consists of an electromagnetic (EM) coil, an eddy-current (EC) coil, and a test specimen. First, the working principle and transduction mechanism in ferromagnetic steel by the designed dual-coil EMAT are analyzed. Then, a finite element model of the designed dual-coil EMAT is established, and the magnetic field and acoustic field distribution of the EM coil are simulated. Finally, a high-temperature experimental platform of flexible dual-coil EMAT is built, and the relationship between the designed EMAT’s received signal waveform and the temperature is analyzed. The results show that the designed EMAT allows the measurement of ferromagnetic steels between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~^{\circ }$ </tex-math></inline-formula>C and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$770~^{\circ }$ </tex-math></inline-formula>C without physical coupling or active cooling.