| 摘要 |
The invention relates to the detection of cracks (35) on an unfinished foundry metal piece (15) by using the eddy currents induced by a coil (11) supplied by an oscillator (13). The invention resides in the fact that, for each point of the piece, measurement is made of the ratio delta F'1/F'1 and the amplitude A'1 of the signal from the oscillator (13), as well as the distance (d) between the coil and the metal piece. The measurements of delta F'1/F'1 and A'1 are corrected to take into account the distance d and are compared with the uncorrected values to give differences D'1 and D'2 which are compared with differences D1 and D2 obtained in the same manner with a reference metal piece and for the same points. Any difference indicates the presence of a defect at the measurement point. <IMAGE>
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