| 摘要 |
PROBLEM TO BE SOLVED: To enable screening for preventing local thinning from being missed in tubular structure defect inspection.SOLUTION: Two angle probes 2, 3 are disposed so as to be adjacent to each other and face inward to make ultrasonic emission directions face each other in the circumferential direction of the outer surface of a tubular structure 1 to be inspected. One of the probes transmits a bulk wave of such a frequency that the wavelength of a transverse wave is smaller than a board thickness at an incident angle for generating a guide wave having a short wave train and weak velocity dispersion in the tubular structure. The other of the probes receives a transmitted wave propagating in the circumferential direction. The other probe receives two-route transmitted waves, a transmitted wave of the bulk wave before the bulk wave is transformed into a guide wave between incident points of the two probes and a transmitted wave of the guide wave transformed from the bulk wave multi-reflected in an area outside the incident points of the two probes, including plural modes, and propagated one round or more in the circumferential direction. A defect of the tubular structure in the whole circumferential direction is detected from the two-route transmitted waves by a transmission method. |
