APPARATUS FOR MEASURING DEPTH OF CRACK BY EDDY CURRENT FLAW DETECTION METHOD

摘要

PURPOSE:To make it possible to quantitatively measure the depth of cracks generated on the surface of a metal in a non-invasive manner, by dividing crack signal amplitude by the signal amplitude corresponding to the electromagnetic characteristic of the metal to be inspected by a crack depth signal calculation part. CONSTITUTION:Signal voltage generated at the time of scanning in such a state that initial voltage and a coil are contacted with a metal 2 to be inspected is processed by a electromagnetical characteristic signal amplitude detection part and outputted from an extraction-of- square-root circuit 64 as a value proportional to the signal amplitude corresponding to the electromagnetic characteristics of the metal 2 to be inspected at each flaw detection point. A signal due to a crack is processed by a crack signal amplitude calculation part and outputted from an extraction-of-square-root circuit 68 as the value proportional to the amplitude of the signal due to the crack. The outputs of the extraction-of-square-root circuits 64, 68 are inputted to a divider circuit 69 constituting a crack depth signal calculation part and the output of he crack signal amplitude calculation part is divided by the output of the electromagnetic characteristic signal amplitude calculation part to output a voltage value which is, in turn, applied to an output terminal 72. The voltage value of the output terminal 72 is corrected on the basis of the electromagnetic characteristic of the metal to be examined at each instantaneous position of the coil to obtain a voltage value proportional to the depth of the crack.