| 摘要 |
PURPOSE:To detect a crack with high accuracy by applying a DC current to the surface of a structural member, detecting a potential distribution by scanning a potential measuring terminal, and comparing this potential distribution with a master curve of a crack which has been derived in advance. CONSTITUTION:A current is supplied to the surface of a structural member 1 from a DC power source 3 through a pair of feeding terminals 2. Also, a measuring terminal 4 is provided between the pair of feeding terminals 2, and a potential distribution of the periphery of a crack 11 is measured. Next, the measuring terminal 4 is scanned through a microcomputer 9 by a driving device 5. From such a potential distribution, a position where the crack 11 is generated and a direction where the crack has been generated are detected, and subsequently, a potential distribution is derived along the detected direction where the crack is generated. This potential distribution and a master curve of a potential distribution of cracks of various shapes which is derives in advance are compared by the computer 9, and a shape of the crack is determined. Accordingly, since the potential of the crack is compared with the master curve which has been derived in advance, the crack can be detected exactly.
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