SIMULATING MATERIALS FAILURE USING PARALLEL MOLECULAR DYNAMICS

Implementing molecular dynamics on the IBM SP parallel computer, we have studied the fracture of two and three dimensional notched solids under tension using in excess of one hundred million atoms. Many recent laboratory findings occur in our simulation experiments. For rapid brittle fracture, one of the most intriguing phenomena is the dynamic instability of the crack tip as it approaches a fraction of the Rayleigh sound speed. A detailed comparison between laboratory and two dimensional computer experiments is presented, and microscopic processes are identified. In particular, an explanation for the limiting velocity of the crack being significantly less than the theoretical limit is provided. For three dimensions, we discover a similar dynamical instability, but now the instability is immediately followed by an unexpected brittle-to-ductile transition giving rise to a proliferation of loop dislocations and the arrest of the crack.