PURPOSE: To inspect a multilayered member having an interface which reflects ultrasonic waves due to a difference in acoustic impedance for the presence/ absence of a defect from the reflected waves of ultrasonic waves.
CONSTITUTION: An inspection device 10 is constituted of an ultrasonic probe 11, an ultrasonic flow detector 13, and a computer 15 which discriminates the presence/absence of a defect by analyzing the frequency of echo waveform signals. A sample 20 is taken from a multilayered member formed by sticking two carbon steel plates 21 and 23 to each other with an epoxy bonding agent 25 and an interface which reflects ultrasonic waves is present in the sample 20 by the difference of the acoustic impedances between the carbon steel and epoxy resin. Therefore, the computer 15 stores the natural frequency of reflected waves from the lowermost layer 23 in advance and, when an echo signal is inputted from the flow detector 13, classifies the echo signal into frequency spectra after Fourier transformation and checks whether or not the component corresponding to the natural frequency is contained in the echo signal. The computer 15 discriminates that the sticking state of the steel plates 21 and 23 is excellent when the component exists, or no-good when the component does not exist.
KOJIMA KATSUHIRO
YAMADA HIYOSHI
