Simulating materials failure by using up to one billion atoms and the world's fastest computer: Brittle fracture

Abstract

We describe the first of two large-scale atomic simulation projects on materials failure performed on the 12-teraflop ASCI (Accelerated Strategic Computing Initiative) White computer at Lawrence Livermore National Laboratory. This is a multimillion-atom simulation study of crack propagation in rapid brittle fracture where the cracks travel faster than the speed of sound. Our finding centers on a bilayer solid that behaves under large strain like an interface crack between a soft (linear) material and a stiff (nonlinear) material. We verify that the crack behavior is dominated by the local (nonlinear) wave speeds, which can be in excess of the conventional sound speeds of a solid.

Figure 1

Variation of elastic modulus as a function of strain under uniaxial stretching in the (110) direction of a FCC crystal formed by the anharmonic (tethered repulsive LJ) potential.

Figure 2

The space-time history of the crack tip for the three different simulations described in the text (reduced units are used).

Figure 3

Snapshot pictures of a crack traveling in the harmonic slab, where the progression in time is from the top to the bottom. The boxed snapshot pictures represent a progression in time from the top to the bottom.

Figure 4

Snapshot pictures of a crack traveling in the anharmonic slab, where the progression in time is from the top to the bottom. The boxed snapshot pictures represent a progression in time from the top to the bottom.

Figure 5

Snapshot pictures of a crack traveling in the mixed slab, where the progression in time is from the top to the bottom. The sound waves associated with the crack's dynamics and the material properties of the harmonic and anharmonic regions of the mixed slab are labeled.