Texture measurements of metal sheets using wideband electromagnetic acoustic transducers

The group velocity of the zero-order symmetric Lamb wave mode (SO) 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 So mode was measured on both aluminium and stainless steel (3 16) sheet. The entire system was computer controlled and the data were processed as acquired. The generation EMAT was driven with a cur-rent 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 So mode Lamb waves than aluminium sheet.