Computation of the radiation pattern of unidirectional SH wave generated by dual-PPM EMATs

Shear horizontal (SH) guided waves are commonly used in non-destructive evaluation and can be generated by permanent magnet electromagnetic acoustic transducers (PPM EMATs). PPM EMATs generate SH waves that propagate either forwards and backwards. This is often an undesired characteristic. Recently, we presented designs of PPM-like EMATs that generate SH waves in a single direction through the interference mechanism of two independent periodic sources of forces. In this paper, we present a line-source based analytical model to calculate the radiation pattern produced by multi-PPM EMATs and, in particular, by dual-PPM EMATs, which are able to generate SH waves in a single direction. The model was validated by computing the radiation pattern of a unidirectional side-shifted dual-PPM EMAT, showing good agreement with experimental and numerical results.