Characterising the beam formation of SH waves using double-row Staggered Halbach EMAT configurations

Abstract

Halbach EMATs can efficiently generate shear horizontal (SH) guided wave modes. Using the Halbach magnet structure, the EMATs can enhance the magnetic flux density within a material forming ultrasonic waves with relatively large amplitude. The paper first presents a comparison analysis of double-row Halbach EMATs with double-row PPM EMATs using Finite Element based simulation models for SH0 ultrasonic wave generation. The study then analyses the wave interference effects created by the staggered double-row Halbach EMAT configurations. This is also performed using numerical Finite Element Models (FEM) and experimentally validated in an Aluminum plate specimen. It is observed that the steering of the ultrasonic guided waves can be associated and predicted for different double-row staggered PPM EMAT configurations.