Abstract
Abstract A high speed photographic (106 frames per second) study has been made of the damage caused to soda-lime and borosilicate glasses by the impact of 1 mm diameter glass and steel spheres travelling at speeds up to 300 ms−1. For velocities up to 180 ms−1, in both glasses cone and radial cracks formed during the loading part of the impact whereas lateral cracks formed during unloading (rebound). At higher velocities, the cone crack was not observed to form in the soda-lime glass whereas in the borosilicate glass it formed up to the maximum velocity studied. The threshold velocity for the formation of lateral cracks in both glasses was found to be in the range 100–120 ms−1 for impact by both glass and steel spheres. Lateral cracks form without any evidence of plastic flow in the glasses. Contact times have been obtained from the photographic sequences and found to agree with quasi-static theories. Finally, possible mechanisms for the formation of radial and lateral cracks are discussed.
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