| 摘要 |
PROBLEM TO BE SOLVED: To precisely discriminate a flaw property, in particular even a flaw extending direction, by a simple method. SOLUTION: A surface 1a within a flaw-detecting range of a testing body 1 is scanned, a half circumference or more of a prescribed circumference of the surface 1a of the body 1 around a scanning position therein as a center is scanned when the presence of a flaw is discriminated, ultrasonic echo signals from an inside of the body 1 relating to ultrasonic signal pulses transmitted from the scanning position into the body 1 in plural precribed scanning angle positions respectively are received, frequency spectrum distributions are found respectively, and a direction orthogonal to a direction connecting the scanning angle position providing the frequency spectrum distribution where the number of ripple valleys of a specified threshold value or less in a preliminarily specified frequency band in the respective frequency spectrum distributions becomes maximum and the scanning position serving as the center is identified as a flaw extending direction. |
