IMPACT, FRACTURE AND FRAGMENTATION (Invited Presentation)

Dynamic fracture and fragmentation processes play a dominant role in the development of the impact cratering record. This presentation seeks to describe these fundamental processes in the context of recent advances in theory, simulation and experiment. We use ultra-high-speed photography (exposure times as short as 20 nanoseconds) to observe the dynamic failure processes in brittle solids, and correlate the high-speed photographs with time-resolved measurements of the stresses in the specimen. Next, we use similar experiments to examine the strength and failure of meteorites. Based on these results and analytical models for dynamically interacting cracks, we construct a scaling model for the strength and failure of brittle solids under impact loading. We explore the implications of this model for impact cratering, the disruption of incoming asteroids, and the formation of regolith on asteroids.