Point-Focusing Shear-Horizontal Guided Wave EMAT Optimization Method Using Orthogonal Test Theory

Abstract

As a class of devices used in sound detection, electromagnetic acoustic transducers (EMATs) have been widely used in the field of nondestructive testing (NDT) owing to their advantages such as contact-free operation, wide applicability, and high performance. However, their low energy-conversion efficiency is the main drawback that limits usage in industrial testing. In this work, we report the effect of different parameters of the point-focusing shear-horizontal EMAT (PFSH-EMAT) on the signal intensity of the receiving transducer. The impact factors of the focusing transducer are as follows: number of magnets in a row m, fan-shaped periodic permanent magnet (FPPM) remanence magnetization Br, coil width w, coil winding number n, aperture angle θ, focal length lF, lift-off distance hl, excitation current frequency fc, and current amplitude Ic. To improve the analysis efficiency, an L32 (49) orthogonal table is used to investigate the nine different factors at four levels, which can be calculated through finite element simulations. The effect of each factor on the signal intensity is obtained by range analysis, and the optimal combination of these impact factors can be achieved by reasonable level selection. Through range analysis, the influence degree of each factor is obtained, and the parameter combination is optimized by analyzing the test results to improve the PFSH-EMAT’s performance. The experimental results show that the optimized PFSH-EMAT is 170% more efficient than the average of the top-three signal intensities in the orthogonal test, which proves the effectiveness of the proposed optimization method.