Detection of Second Harmonic Wave from the Closed Crack Using Finite amplitude Ultrasonic Wave

Detection method for the closed crack existed in the glass plate using finite amplitude ultrasonic guided wave is described. The received signal is analyzed by the wavelet transform to identify the mode of the guided wave using group velocity dispersion curves. As the results, finite amplitude Rayleigh wave propagation is identified. Using the finite amplitude Rayleigh wave, increase in 6 dB of the second harmonic components generated from a closed crack in the glass plate is observed. Rapid increase of the second harmonic component at the condition that width of closed crack, less than 2 nm, is equal to the vibration amplitude of Rayleigh wave is also found out. Potential of closed crack detection is clarified by the use of finite amplitude guided wave system