Disbond Detection and Characterization Using Horizontally Polarized Shear Waves and EMAT Probes

Horizontally polarized shear waves offer high sensitivity for inspection of adhesively bonded structures. They produce a strong shear deformation on the adherent-adhesive interface allowing a relatively direct estimation of the adhesive failure (disbonds). Compared to localized conventional point-by-point ultrasonic waves, horizontal shear guided waves can be launched over long distances and larger areas of structural parts can be covered. Guided horizontal shear waves have a multimodal character and do not exhibit mode conversion at interfaces. The first fundamental symmetric shear mode (HS0) propagates non-dispersively in isotropic materials, while higher orders modes are dispersive and behave as guided Lamb waves