A Novel Shear Horizontal Guided Wave EMAT With Periodic Solenoid Coils and a Single Magnet

Periodic permanent magnet (PPM) electromagnetic acoustic transducers (EMATs) are commonly employed to generate shear horizontal (SH) guided waves for defect scanning in steel structures. During scanning, electromagnets can be used as alternatives to permanent magnets to generate static bias magnetic fields, thereby addressing the problem of permanent magnets attracting iron filings on the surface of steel structures. However, since the PPM EMATs have multiple magnet units and complex magnetic field distributions, replacing permanent magnets with electromagnets presents significant challenges. In this article, a novel SH guided wave EMAT with periodic solenoid coils (PSCs) and a single magnet (referred to as the PSC EMAT) was developed. The design methodology for the PSC EMATs was presented using the excitation of the single SH0 mode guided waves in a steel plate as a case study. The transduction process and excitation performance of the PSC EMATs were analyzed through both finite element (FE) simulations and experimental investigations. The results from both simulations and experiments demonstrate that the PSC EMAT can effectively generate single SH0 mode guided waves that propagate in four directions, with the forward directions identified as the primary orientations for defect inspection. These findings indicate that PSC EMATs can reliably generate and receive SH guided waves using a simplified static bias magnetic field, providing a foundation for the future application of electromagnets.