| 摘要 |
PURPOSE:To execute the defect flaw detection of all azimuths of a weld zone, for minimizing the oscillation angle and making the scanning time the shortest by the minimum number of probes by allowing three probes to transmit and receive an ultrasonic beam by four modes. CONSTITUTION:Three pieces of probes 1 by which an ultrasonic beam is transmitted and received in the 45 deg. direction against a weld line 30, and which has been placed so that the ultrasonic beans join at one point in the vicinity of the weld line are fixed to a scanner 2, and a flaw detection is executed by four transmission and reception modes (a)-(d) in the weld line direction along a rectangular scanning line. In this state, a reflected echo from an azimuth of an arbitrary defect 4 becomes such a mountain-like distribution as gives a peak at every 45 pitches extending from 0 deg. to 180 deg., based on the weld line vertical direction as a reference. In case of scanning the probe 1 by a fixed mode, a defect of an azimuth in the vicinity of 22.5 deg. pitch is generally smaller than an echo threshold. Therefore, when the scanner 2 is moved, while allowing it to execute a reciprocating rotation several times each centering around a transverse axis point 3 at which the ultrasonic beams join, to match a rectangular scan, a mountain of the echo expands, and the defect is detected surely even in the vicinity of 22.5 deg.. |
