Size effects on the wave propagation and deformation pattern in copper nanobars under symmetric longitudinal impact loading
S Jiang and Z Chen and Y Gan and SY Oloriegbe and TD Sewell and DL Thompson, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 45, 475305 (2012).
Molecular dynamics simulations were performed to study the influence of system size on wave propagation and deformation patterns in < 1 0 0 >/1 0 0 copper nanobars with square cross-section under symmetric longitudinal impact loading. Nanobars of longitudinal length 100a with cross-sectional edge lengths h = 10a, 20a, and 40a were impacted on both ends by flyers of size 20a x h x h, where a is the Cu unit cell length, and impact speed 500 ms(-1). For reference, quasi-infinite slab samples with periodic cross-sectional edge lengths 10a and 40a were also studied. It was found that the wave propagation speed increases with increasing cross-sectional area and eventually approaches the value obtained for a quasi-infinite sample. Extensive plasticity occurs across the entire length of the nanobars, whereas the quasi-infinite samples remain in the elastic regime and exhibit a vibrating (ringing) behaviour. The deformation pattern in the nanobars is strongly dependent on the cross-sectional area. For the nanobar with h = 10a the material fully reorients from < 1 0 0 >/1 0 0 to < 1 1 0 >/1 1 1 with few stacking faults and twins. Material in the nanobar with h = 20a does not reorient completely; the local crystal deformation is mediated mainly by a partial dislocation activity leading to predominantly non-intersecting stacking faults and twins. Nanobars with h = 40a exhibit behaviour similar to that for the h = 20a case but with greater propensity for intersecting stacking faults.
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