An nondestructive experimental system to estimate the elasticity constants of thin plates using ultrasonic guided waves (lamb waves) in real time was described in this presention. The method measures the dispersion curves of the guided waves (lamb waves) for the lowest symmetric mode. Spectral analysis is applied to measure the phase shift of a guided waves as detected by two piezoelectric probe in contact with the plate. This method automatically calculates the phase velocity in a continuous range of frequencies that depends on the transducers bandwidth. The method automatically sets the test frequency, acquires the data, does the spectral analysis and displays the dispersion curves. The Young's modulus and the shear modulus are calculated from the measurements of phase velocity by an inversion algorithm. The system, tested in aluminum plates of different thickness, measured the phase velocity with and accuracy of 1 % respect to the theoretical curves. |
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