High-Temperature Transduction Efficiency Analysis of the Lorentz Force Mechanism EMAT

Electromagnetic acoustic transducers (EMATs) are noncontact in nature and eliminate the need for couplants, offering extensive potential for applications in high-temperature measurements. However, a main disadvantage of the EMAT is its low transduction efficiency, particularly in the Lorentz force mechanism, where the efficiency further decreases at elevated temperatures, often resulting in ultrasonic signals being obscured by noise; this is a challenge for the high-temperature application of the Lorentz force mechanism EMAT, but the reasons behind the temperature-induced efficiency loss have not been fully solved in existing research. Therefore, this article proposes an analysis method to investigate the transduction efficiency of the Lorentz force mechanism EMAT at high temperatures, with the aim of identifying effective ways to increase its performance. Analytical expressions for ultrasonic wave generation and reception of the Lorentz force mechanism EMAT are derived, followed by validation through a finite element (FE) model. By combining analytical calculation solutions with experimental results, the impact of temperature-dependent parameters on the transduction efficiency is investigated and improvement methods are proposed. The research results provide a foundation for the optimal design of high-temperature Lorentz force mechanism EMATs.