| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detector capable of unidirectionally transmitting unimodal Lamb waves. SOLUTION: The ultrasonic flaw detector is provided with: a transmitter / receiver group A composed of four transmitting / receiving elements 4a-4d which are arranged at equal intervals along the circumference of a tube 1; a similarly structured transmitter / receiver group B; a control section 8 selecting one as a transmitting element and at least one as a receiving element from eight transmitting / receiving elements 4a-4h, changing the selected combination of the transmitting element and the receiving element, and carrying out a plurality of transmissions and receptions; and a signal processing section 6 summing a plurality of received signals obtained by the plurality of transmissions and receptions until the lowest order torsion mode gets dominative, calculating correction factors corresponding to respective contact states of the transmitting / receiving elements from peak magnitude ratios of the summed signals, correcting the plurality of received signals respectively based on the correction factors, composing them, carrying out time shift processing, and outputting a flaw detection result including information of identified directions in which the received signals are transmitted. COPYRIGHT: (C)2005,JPO&NCIPI
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