Impact of Small Steel Spheres on the Surfaces of “Normal” and “Anomalous” Glasses

High‐speed photography (framing rate of 10 6 s ‐1 ) has been used to follow the formation and growth of damage in a number of oxide glasses when impacted with 1‐mm‐diameter steel balls at velocities of 150 m· s ‐1 or higher. Silicate, germanate, and borate glasses were studied in order to clarify the importance of “anomalous” vs “normal” elastic characteristics on their impact behavior. As expected it was found that glasses in these systems which are “anomalous” showed impact behavior which had earlier been seen in silica and borosilicate glass, whiie those glasses which are “normal” showed behavior similar to that shown by soda‐lime silica glass. On the other hand, although B 2 O 3 has been characterized as “normal,” its impact, as well as its quasi‐static behavior, appears to put it in a class by itself. In this case, no cracking is observed during loading up to 150 m·s ‐1 , while radial and lateral cracking are seen during unloading.