| 摘要 |
PURPOSE:To detect presence or absence of a crack positively and simply even if the crack exists internally and does not appear on the surface. CONSTITUTION:A support part 8 holds one part of a ring-shaped object 10 from both surfaces for fixing. Vibrators 3 and 4 are placed on the surface of the ring-shaped object 10 at both left and right sides of the support part 8 and also a vibrator sensor 5 is placed out the surface of the ring-shaped object 10 which opposes the support part 8. A switching control part 2 receives an oscillation signal S1 from an oscillation part 1 and switches it alternately and then transmits it the vibrators 3 and 4 and at the same time transmits a switching timing signal S2 to a criterion part 7. The vibrators 3 and 4 alternately receive oscillation signals S3 and S4 and then apply a vibration with an equal strength to the ring-shaped object 10. The vibration sensor 5 detects vibrations which are propagated alternately from the vibrators 3 and 4 and a vibration detection part 6 receives the output of the vibration sensor 5 and then detects the vibration strength. The criterion part 7 compares the vibration strength according to the timing signal S2 and then judges the presence or absence of a crack. |
