Patent ID: 8266966

Claim:
An ultrasonic exploration method configured to execute: an exploration process for executing an exploration operation, in which a transmission/reception position, at which ultrasonic waves at a specified frequency are transmitted to an exploration-target area of an exploration-target metal body and reflected waves of the ultrasonic waves are received, is sequentially changed by a specified pitch distance, for each of a plurality of preset incident angles of the ultrasonic waves, extracting harmonic waves contained in the reflected waves for each of the incident angles, and generating for each of the incident angles a nonlinear image of the exploration-target area in which echo signals acquired from the harmonic waves are presented on the basis of a response time from transmission of the ultrasonic waves to reception of the reflected waves; an image conversion process for converting the nonlinear image for each of the incident angles so as to conform to a frame form matching a cross-sectional shape of the exploration-target area on the basis of a refraction angle, at which the ultrasonic waves transmitted at the incident angle propagate in the exploration-target metal body, and the number of data prescribed in accordance with the refraction angle and a sonic speed of the ultrasonic waves to generate a frame conversion image for each of the incident angles; and an exploration image generation process for determining in advance a signal intensity threshold for removing echo signals resulting from an orientation defect due to a mismatched crystal orientation in a crystal structure of the exploration-target metal body, and overlapping frame conversion images formed by only echo signals whose signal intensity is the signal intensity threshold or more to generate a nonlinear exploration image of the exploration-target area.