Texture measurements of metal sheets using wideband electromagnetic acoustic transducers

The group velocity of the zero-order symmetric Lamb wave mode (S 0 ) has been measured on metal sheet as a function of angle to the rolling direction. Generation and detection of the Lamb wave was achieved using wideband non-contact ultrasonic electromagnetic acoustic transducers (EMATs). The EMATs were relatively small in size and employed permanent NdFeB magnets. The angular dependent velocity of the S 0 mode was measured on both aluminium and stainless steel (316) sheet. The entire system was computer controlled and the data were processed as acquired. The generation EMAT was driven with a current pulse of 270 A (peak value). This high current level gave rise to a more powerful generation source than is usually obtained with EMATs, enabling measurements to be made on stainless steel sheet which is much less efficient for EMAT generation of S 0 mode Lamb waves than aluminium sheet.