Transition from damage to fragmentation in collision of solids

We investigate fracture and fragmentation of solids due to impact at low en ergies using a two-dimensional dynamical model of granular solids. Simulati ng collisions of two solid disks, we show that, depending on the initial en ergy, the outcome of a collision process can be classified into two states: a damaged state and a fragmented state, with a sharp transition in between . We give numerical evidence that the transition point between the two stat es behaves as a critical point, and we discuss the possible mechanism of th e transition. [S1063-651X(99)15302-9].