Precision laser-ultrasonic velocity measurement and elastic constant determination

Abstract A laser-ultrasonic method to measure the acoustic velocities and the elastic constants of solid materials based on the crosscorrelation of successive echoes is presented. Measurements are performed in the thermoelastic regime or slight ablation regime, which permits simultaneous measurement of longitudinal shear velocities and an unlimited number of shots at the specimen. Diffraction corrections are calculated, and dispersion effects are evaluated by frequency analysis. The precision and accuracy of the technique are estimated in terms of sampling rate, thickness of the sample, signal-to-noise ratio, frequency bandwidth and laser-beam alignment. Examples of applications of the technique are given for PZT ceramic, metal-ceramic composites and single crystal germanium.

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