| 摘要 |
PROBLEM TO BE SOLVED: To precisely measure a minute crack 3 generated on the inner surface of a pipe 2. SOLUTION: A focusing ultrasonic probe 11 is arranged in a base position having a required distance from a welded joint on the outer surface of a pipe 2 along the pipe axial direction 16, and the ultrasonic probe 11 is scanned over the whole circumference while shifting the position by a minute pitch of 1-5 deg. in the circumferential direction 33. Three kinds of reflected waves 5 of the reflected wave 5 obtained by making an ultrasonic wave 4 incident on the welded joint 12 from the pipe axial direction 16, the reflected wave 5 obtained by making the ultrasonic wave 4 incident on the welded joint 12 with an inclination of 5-15 deg. from the pipe axial direction 16, and the reflected wave 5 obtained by making the ultrasonic wave 4 incident on the welded joint 12 with an inclination of -5 deg. to -15 deg. from the pipe axial direction 16 are measured, and the maximum value of the three reflected waves 5 from the same reaching position is adapted to estimate the shape of a crack 3. |
