Measurement of strain in a shock loaded, high-density glass.

Longitudinal strain has been measured in DEDF (Type D, Extra Dense Flint), a high-density, lead-filled glass, over the stress range 2.0 GPa to 4.5 GPa (the supposed Hugoniot Elastic Limit -- HEL). Such glasses have been shown to fail in compression across a front which has been called the failure wave. Strain gauges have been mounted either near the impact face, such that the effect of failure may be observed, or near the rear (free) surface, such that the failure wave does not enter the gauge location. Below the stress at which the glass first supports a failure wave, measured strains agree well with values calculated from using elastic relations. Above this stress, the arrival of the failure wave results in an increase in compressive strain, and this has been correlated with the measurements of other variables such as lateral stress. Interestingly, only the measured values of strain behind the failure wave agree with calculated strains. [ABSTRACT FROM AUTHOR]