TABLE I.
Stone dimensions and properties of the materials used in the experiment and modeling. The stone is made from a low-viscosity infusion epoxy (Wessex Resins and Adhesives, Hampshire, UK). The photoelastic constant was estimated from the polariscope images for blue light with a 0.45 μm wavelength. The immersion liquid is Benzyl benzoate (Sigma-Aldrich Corp., MO), which has a refractive index matching the epoxy. Hydrophone measurements were performed in water, and the water values are used to convert the pressures to those obtained in the immersion liquid. Acoustically, the liquid and water are well matched to minimize the effect on the acoustics. The low index of refraction of water also shows why the immersion liquid was needed.
| Parameter | Value |
|---|---|
| Stone length (mm) | 20.8 |
| Stone diameter (mm) | 6.3 |
| Stone density, ρ (kg/m3) | 1100 |
| Stone longitudinal velocity, cl (m/s) | 2440 |
| Stone shear velocity, ct (m/s) | 1295 |
| Stone refractive index, n | 1.58 |
| Stone photoelastic constant, C0 (Pa−1 m−1) | 2.4 × 10−4 |
| Immersion liquid density, ρ (kg/m3) | 1100 |
| Immersion liquid speed of sound, c (m/s) | 1493 |
| Immersion liquid refractive index, n | 1.58 |
| Water density, ρ (kg/m3) | 1000 |
| Water speed of sound, c (m/s) | 1500 |
| Water refractive index, n | 1.33 |