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

Over the last ten years several observations have been made of compressive failure in glass by a so called fracture wave. A high-speed photographic study has been conducted in order to observe the propagation of fracture waves in glass. Streak and framing photography have been used to determine details of the wave speed and surface structure of fracture 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 of exposure and interframe times from 50 ns upwards. Simultaneous measurements of the longitudinal stresses were made using manganin pressure gauges embedded in the samples. Results will be presented showing separation between the shock and fracture fronts suggesting that the failure mechanism is by compression rather than resulting from relief waves propagating from the free surfaces.