Molecular dynamics simulations of the initial stages of spall in nanocrystalline copper

Molecular dynamics simulations of the initial stages of the spall process in single nanocrystals and polynanocrystals of copper are performed. The simulations show that void nucleation in copper polynanocrystals occurs predominantly along the grain boundaries, whereas voids are formed at stacking fault intersections in copper monocrystals. The calculated spall strengths of single-crystal copper at strain rates of 2-4x10(9) s(-1) are consistent with existing experimental data, and the polynanocrystal spall strength is found to increase rapidly at rates around 10(9) s(-1) up to the theoretical ultimate spall strength of 22.5 GPa at about 3x10(9) s(-1).