New design of electromagnetic acoustic transducer for precise determination of defect

New design of a EMAT with magnetic coils, named as current driven EMATs, was proposed to improve its performance for nondestructive inspection. The magnetic coils were connected to a pulse forming network circuit which can flow the large rectangular current to generate strong magnetic field in a short time. The detection profiles of shear horizontal waves were compared for this current driven EMAT and the conventional periodic permanents structure EMAT. The both profiles were almost the same which indicated that the current driven EMAT has suitable configuration for generating the shear horizontal waves. The amplitudes of the detected waves were increased with mangetomotive force. When the two sheets of the magnetic coils were stacked, the amplitudes of the waves were increased to 2.3 times larger than that of the conventional EMAT. Due to the improvement of the performance of the EMAT, the defect inspection at a frequency of 2.4 MHz can be performed with the high sensitivity.