Patent ID: 7600442

Claim:
An ultrasonic probing method utilizing a resonance phenomenon, by which: a step function voltage is applied to a vibrator in a transmission probe; and a wide band ultrasonic wave is continuously transmitted from the transmission probe and a wide band ultrasonic wave from the probing target is received by a receiving probe; wherein a measurement is performed in the state where the transmission probe and the receiving probe are located away from each other on a surface of the probing target, the method having: a receiving function of obtaining a received wave G j (t) each time the position of each of the probes is changed; an arithmetic operation function of obtaining a spectrum F j (f) corresponding to the received wave G j (t) by Fourier transformation; a display function of providing a comparative display of the received wave G j (t) and the spectrum F j (f) at measurement points j; a function of generating longitudinal cursors f 1 , 2 f 1 , 3 f 1 , . . . , n A f 1 on a screen of the comparative display of the spectrum F j (f), and changing the positions of the longitudinal cursors to match each of all the cursors to a rising spectrum peak having a large value; a function of performing an arithmetic operation/display of a thickness W of the probing target from the values of the longitudinal cursors and a sonic velocity V P of the probing target; and a function of obtaining a longitudinal cursor f S1 by an arithmetic operation of f S1 =γ 1 ·f 1 using a sonic ratio γ 1 between a transverse wave and a longitudinal wave of the probing target, generating longitudinal cursors f S1 , f S2 , f S3 , . . . , n A f S1 on the screen of the comparative display of the spectrum F j (f), and changing the positions of the longitudinal cursors by a small amount to match the cursors, which are obtained by multiplying the longitudinal cursor f S1 by an integer, to a rising spectrum peak having a relatively small value; the method comprising: a first step of extracting a narrow band spectrum FA j (f) of a frequency of n B ·f S1 from the spectrum F j (f) using an integer n B of 1 or greater, and obtaining a component wave GA j (t) corresponding to the narrow band spectrum FA j (f) by inverse Fourier transformation; a second step of providing a comparative display of the component wave GA j (t) using predetermined sizing coefficients n S1 , n S2 and n S3 ; and a third step of determining the position of a flaw inside the probing target right below a line segment connecting the center of the transmission probe and the center of the receiving probe, based on at which of the measurement points a wave can be confirmed to be generated on the screen of the comparative display of the component wave GA j (t).