Medium characterization from interface-wave impedance and ellipticity using simultaneous displacement and pressure...

Area of Science:

• Acoustics
• Materials Science
• Wave Physics

Background:

• Interface waves, such as pseudo-Rayleigh (pR) and Stoneley (St) waves, offer valuable insights into fluid/elastic-solid interactions.
• Wave attributes like impedance and ellipticity are crucial for characterizing these interfaces but have complex dependencies on material properties.

Purpose of the Study:

• To develop a robust method for estimating elastic properties (Young's modulus and Poisson's ratio) at fluid/elastic-solid interfaces.
• To validate the proposed method using experimental measurements of pR wave impedance.

Main Methods:

• Combined interface wave attributes (impedance and ellipticity) into a cost function for stable parameter estimation.
• Employed laser Doppler vibrometry (LDV) for particle displacement and needle hydrophone for fluid pressure measurements.
• Utilized a model to account for refractive index perturbations affecting LDV measurements.

Main Results:

• Successfully extracted the impedance of a laser-excited pR wave at a water/aluminum interface.
• Predicted a 28% impedance decrease for the pR wave compared to plane wave impedance, accounting for LDV perturbations.
• Observed excellent agreement between predicted and experimentally extracted pR waveforms in both displacement and pressure.

Conclusions:

• Combining interface wave attributes provides unique and stable estimates of material properties.
• The experimental validation confirms the efficacy of the method for characterizing fluid/elastic-solid interfaces.
• Accurate waveform prediction, even with measurement perturbations, highlights the method's reliability.