Thermoelastic impact damage on glass

Abstract

Etched, as-received and abraded float glass, and etched low-expansion borosilicate glass were impacted at a velocity of 5.62 m/s by a spherical steel impactor of 10.3 mm diameter. The temperature of the glass specimens and that of the impactor were varied, and the effect of thermal shock on the resulting impact damage was investigated. The number, density and the radial spread of inner ring cracks that formed inside the primary ring crack, and the probability of cone crack formation were observed to increase significantly with increasing temperature difference between the impacting bodies, and with the abrasion of the glass surfaces prior to impact. Impacts on soda-lime-silica float glass at specimen temperatures of 700 and 750 °C revealed inner ring cracks without cone cracks, suggesting that significant strength degradation may result in glasses under these impact conditions. Borosilicate glass was found to be much more resistant to inner ring crack formation than soda-lime-silica glass.