PURPOSE: To make it possible to execute flaw detection at a high temperature without surface treatment of a body to be inspected, by a method wherein juxtaposed coils are switched over selectively electrically and the direction of advance of an ultrasonic wave generated from each coil is changed by changing the frequency of a pulse current supplied.
CONSTITUTION: A plurality of coils 51, 52... are juxtaposed in the direction intersecting the direction of propagation of an ultrasonic wave perpendicularly to it. When a flaw detection frequency is changed, an angle θ of refraction changes. By changing gradually the flaw detection frequency of a pulse current generated by an oscillation circuit, scanning can be executed by one coil 5 with the direction of flaw detection varied in a prescribed range and scanning over a wide range can be executed with a relatively small coil. By making the coils 51, 52... active sequentially by turning an electronic switch ON/OFF selectively, the angle θ of refraction changes through the whole area of installation of the transmission/reception coils 5 without being accompanied by mechanical movement, jointly with the scanning on the basis of the change in the angle θof refraction, and flaw detection can be executed with a relatively fine scanning pitch.
HAYASHI KAZUO
TAWARAGUCHI TAKAO
UDAGAWA KENJI
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