Optimal Design of Point-Focusing Shear Vertical Wave Electromagnetic Ultrasonic Transducers Based on Orthogonal Test Method

Abstract

The lower conversion efficiency is the main drawback of electromagnetic acoustic transducers (EMATs) compared with other transducers, which limits their use in many industrial applications. In this paper, for enhancing the performance of point-focusing shear vertical wave EMATs (PFSV-EMATs), 18 orthogonal tests with seven factors and three levels are conducted through finite-element simulations. First, the degree of seven factors on the signal amplitude, axial focus offset, and radial focus offset is obtained by range analysis and compared. It indicates that the effect of the liftoff distance and the exciting current on signal amplitude is the largest, while the effect of the inner radius of concentric meander-line coils on the axial and radial focal offset is the largest. Then, the influence degree of various factors on test results is analyzed at frequencies of 1.5, 2, and 2.5 MHz, showing that the relatively low frequency, i.e., the sparser coil spacing, is favorable for signal amplitude and detrimental for point-focusing ability. Finally, experiments are carried out to verify the validation of optimization results, which indicates that the increased signal amplitude of 88.78%, smaller axial focus offset, and zero radial focus offset can be achieved by the optimized PFSV-EMAT, which has the improved signal amplitude and point-focusing behavior, compared with the non-optimized one.