Optimal Design of Lamb Wave Electromagnetic Acoustic Transducers for Improving Their Excitation Performance

Abstract

An optimal design method for improving the excitation performance of the Lamb wave electromagnetic acoustic transducers (EMATs) is proposed to minimize the influence of multi-mode and dispersion and to increase the signal strength of Lamb waves concurrently. The method combines the “two-intersection-points” method and “zero-slope” criterion with the orthogonal test method. Nine prime parameters of Lamb wave EMATs are optimized and the influences of parameters on Lamb wave signal strength are obtained. Analysis indicates that the spacing interval of the coil and the working frequency of the transducers determine multi-mode and dispersion characteristics of Lamb waves, and lift-off distance, excitation current, magnet thickness and conductor width play a significant role in the signal strength. Experimentation shows that, after optimization, not only are the multi-mode and dispersion phenomena of Lamb waves minimized, but also the signal amplitude is increased by 216%, which verifies the validity of the proposed method.