| 摘要 |
PURPOSE:To attain to enhance flaw detection capacity, by allowing ultrasonic beam to be incident on the doughnut like elongated part of the flat part of the head part of a hexagon head bolt while converging the ultrasonic beam. CONSTITUTION:A hexagon socket head bolt 11 is set in water 16 and a converging type probe 18 having an acoustic lens 17 mounted thereon is arranged in the vicinity of the surface of the water. The probe 18 is arranged so that the converging range of the ultrasonic beam 19 emitted therefrom is set to the plane part 15 of the head part 12 of the bolt 11. Because the bolt head part 12 has an elongated doughnut shape, the shape of said beam is set so as not to exceed the width of said head part 12. Next, the probe 18 is arranged so as to be inclined with respect to the plane part 15 of the bolt 11 and a longitudinal wave is incident on the probe 18 from underwater and a transversal wave generated by mode conversion is allowed to be incident to the bolt head part 12 and the incident transversal wave is once reflected from the outer peripheral surface of the bolt head part 12 to be allowed to reach a neck throat part 21. If a flaw is present in the throat part 21, the reflected wave therefrom propagates through a reverse route to be received as a flaw echo by the probe 18. by By this method, high flaw detection capacity is obtained.
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