The accuracy of acoustic birefringence shear wave measurements in sheet metal

In rolled metal sheet the through thickness shear wave energy is steered into two orthogonal polarizations, 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 polarized electromagnetic acoustic transducer (EMAT) do not correspond with that obtained using a radially polarized EMAT. An analytical model has been developed, which explains the source of this effect from the using the fast Fourier transform. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3033395]