A HIGH-SPEED PHOTOGRAPHIC STUDY OF FRACTURE WAVE-PROPAGATION IN GLASSES

Over the last ten years several observations have been made of compres sive failure in glass by a so called fracture wave. A high-speed photo graphic study has been conducted in order to observe the propagation o f fracture waves in glass. Streak and framing photography have been us ed to determine details of the wave speed and surface structure of fra cture waves induced in glasses by planar impact. A 50 mm single stage gas gun was used to launch copper flyer plates at velocities of up to 1 km s(-1). A computer controlled high-speed camera was used capable o f exposure and interframe times from 50 ns upwards. Simultaneous measu rements of the longitudinal stresses were made using manganin pressure gauges embedded in the samples. Results will be presented showing sep aration between the shock and fracture fronts suggesting that the fail ure mechanism is by compression rather than resulting from relief wave s propagating from the free surfaces.