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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 5 0 mm single stage gas gun was used to launch copper flyer plates at velocities of up to 1 km s-l. A computer controlled high-speed camera was used capable of exposure and interframe times from 5 0 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.1.

Experiments were conducted to investigate the mechanisms of damage to brittle materials by liquid-jet impact as seen in cavitation or simulated rain erosion. In this work, a liquid-jet of 3 mm in diameter and speed ca. 600 m s −1 , produced using the single-impact jet apparatus (SIJA), was impacted on a polymethylmethacrylate (PMMA) target, chosen as a representative brittle solid. Damage was produced by the liquid jet both near the surface of, and within the bulk of the target. These failure phenomena, which proceeded in several stages, were observed in detail by means of a high-speed camera and with the aid of schlieren visualization techniques. The damage introduced resulted from the interactions of stress waves (compressive, tensile and shear) within the target. A surface ring crack was produced behind a propagating release wave. A central crack along the axis of the jet was also produced by interaction of these waves and, in the case of targets of finite thickness, spall damage was observed at the rear surface. A further crack was opened by the interaction of a shear wave with a reflected release. All the failure mechanisms resulted from wave interactions induced in the target and occurred within a few microseconds of impact.

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