Index of refraction and mechanical behavior of soda lime glass under shock and release wave propagations

This article reports a set of experiments designed to measure change in the refractive index of transparent material under both planar shock and release wave propagations. Information about both mechanical and optical properties of transparent material were obtained simultaneously through the measurement of particle velocity at or near the impact surface and the free surface velocity. Data thus obtained is used to determine shock and release wave velocities and the Hugoniot elastic limit (HEL) of the material. Shock wave velocity in soda lime glass remains unchanged at 5.83 +/- 0.04 km/s, i.e., equal to the measured ultrasonic longitudinal wave velocity, when it is shock compressed to less than or equal to 4.3 GPa. The value of shock wave velocity begins to decline when the impact stress in the glass exceeds this value. The release wave velocity, however, remains equal to the measured ultrasonic longitudinal wave velocity to only 3 GPa, it begins to decline at higher stresses. The variation in the refractive index of the glass shows a cusp at 3.04-3.14 GPa. Additionally, up to and including the impact stress of 3.14 GPa, the refractive index after shock compression and release is within 1% of its ambient value, but at higher stresses it differs by larger percentage points. The HEL of the glass is determined to be 3.10 +/- 0.06 GPa although it lacks the classic well defined cusp in all the recorded wave profiles of soda lime glass. (C) 1998 American Institute of Physics. [S0021-8979(98)00724-5].