Analytical modeling and analysis of Rayleigh-wave EMATs considering both the horizontal and vertical magnetic fields

Electromagnetic acoustic transducers (EMATs) suffer from inherently low transduction efficiency. Recent studies have demonstrated that the horizontal magnetic fields can significantly enhance the signal amplitude of Lorentz force-based EMATs. However, conventional analytical models primarily account for the effects of the vertical magnetic fields, while overlooking the excitation contribution of the horizontal magnetic fields, thereby limiting efforts to improve EMAT performance. In this work, the electromagnetic ultrasonic testing process using Rayleigh waves is systematically divided into three stages: excitation, propagation, and reception. Theoretical models are developed for each stage. Based on this framework, an analytical model incorporating both the vertical and horizontal magnetic fields is established. Experimental results from various coil configurations demonstrate that the proposed theoretical model can accurately compute the ultrasonic signals within the test specimen. Furthermore, the analytical model is employed to investigate the effect of magnet width on the amplitude and distortion level of the received signal. The findings reveal that when the magnet width is equal to the overall width of the coil, the received signal achieves the maximum amplitude with relatively low distortion.