| 摘要 |
PURPOSE:To detect a crack with a high reliability and a high accuracy as generated in a clamp bolt of a nuclear pressure cylinder or the like, by inserting a pair of angle beam probes and a vertical probe into an insertion hole for a heating wire of the bolt filled with a coupling liquid. CONSTITUTION:A feed rod 11 which is inserted into an insertion hole 4 for a heating wire for shrinkage fitting of a bolt 2 and supported with a stationary support 12 is rotated and moved up and down with a driver. A ultrasonic probe comprising a vertical probe 50 and pairs of angle beam probes 45, 46, 47 and 48 is provided on the axis of the feed rod 11 to transmit or receive an ultrasonic wave. Ultrasonic waves oscillated by the probes 45-48 and 50 are made incident into the bolt 2 through a coupling liquid circulated into the insertion hole 4. Circumferential thickness of the bolt is measured with the vertical probe 50 while a thread and a crack are detected with the angle beam probes 45-48. The flaw detection data are sent to a signal processor 59 together with detection data from a angle of rotation detector 18 and a feed detector 43 to process and then, displayed on a CRT 71 of an ultrasonic flaw detector 58.
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