Patent ID: 8776603

Claim:
A non-destructive testing method comprising the steps of: entering a single-pulse ultrasonic wave signal from a pulse entering section into an object to be tested, the single-pulse ultrasonic wave signal having one or two periods and a frequency of 1 MHz to 10 MHz; receiving the single-pulse ultrasonic wave signal, which has been entered into the object to be tested, in a receiving section; and approximating an attenuation waveform u(t) of the received single-pulse ultrasonic wave signal using an approximation equation of u(t)=A(t)sin φ(t) where t stands for time, A(t) for an envelope line of the attenuation waveform and φ(t) for a phase at time t; obtaining an instantaneous angular frequency at time t from the phase in the approximation equation; obtaining an instantaneous frequency at time t from the instantaneous angular frequency; and diagnosing a condition of the object to be tested, based on temporal change of the instantaneous frequency.