ANALYTICAL EXAMINATION OF TEMPORAL AND FREQUENCY DOMAIN INTERFERENCE DUE TO ACOUSTIC BIREFRINGENCE IN THIN SHEETS USING ELECTROMAGNETIC ACOUSTIC TRANSDUCERS (EMATS)

摘要

In rolled metal sheet the through thickness shear wave energy is steered into two orthogonal polarisations, parallel and perpendicular to the sheet's rolling direction. Ultrasonic velocity measurements used to determine the orientation distribution coefficients in thin sheets can be obtained from the fast Fourier Transform of the time domain signal. It is observed that the data obtained using a linearly polarised EMAT does not correspond with that obtained using a radially polarised EMAT. An analytical model was developed which explains the source of the effect from the transform.