| 摘要 |
PURPOSE:To easily and surely detect the presence or absence of a defect in the screw threads in the joint part of a pipe by detecting the presence or absence of a reflection echo while spirally moving an ultrasonic probe by directing the emission beam thereof toward the base direction of the screw threads. CONSTITUTION:The ultrasonic probe 3 is mounted to one end of a moving body 4 screwed to the screw threads 10 so as to come into contact with the surface of the outside cylinder of an internal thread part 1a. A swiveling driving device 5 and a feeder 6 are controlled by an NC (numerical control) device 11. The moving body 4 is spirally moved on the outside cylindrical surface of the internal thread 1a in such a manner that the emission beam from the probe 3 moves along the thread base of the internal thread 1a by the cooperative movements of these devices. The mounting position of the probe 3 and the directing direction of the emission beam are previously so determined that the angle theta between the side face 22 of the thread ridge and the incident direction of the emission beam 20 of the probe 3 attains <=80 deg. (>=10 deg. inclination in the direction orthogonal with the side face 22 of the thread ridge). The emission beam from the probe 3 reflects at the defect 12 of the thread face and the reflected beam is received by the probe 3, by which said beam is detected as the defect echo. |
