Sample Size Dependence of Crack-tip Microstructure and Stress Evolutions in Single Crystal Nickel
WP Wu and ZZ Yao, CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES, 93, 235-252 (2013).
The internal microstructure evolution and atomic stress distribution around the crack tip of a pre-cracked single crystal nickel with unequal sample sizes are studied by molecular dynamics (MD) simulation. The simulated results indicate that the crack propagation dynamics and stress distributions around the crack tip are strongly dependent on the microstructure evolution caused by the change of sample size. Unequal sample sizes induce various atomic configurations around the crack tip during the crack propagation. When atomic configuration is invariable around the crack tip, the crack grows rapidly along the crack path, the stress concentration occurs at the crack tip of growing crack and the stress is monotonic along the crack path. Once the occurrence of microstructure evolution (void nucleation, deformation twinning) around the crack tip, the crack grows slowly and the stress value is variable along the crack,path due to the peak stress is accompanied by the appearance of the void and deformation twinning ahead of the crack tip. The pre-cracked single crystal nickel under mode I loading condition shows the different crack propagation dynamics and stress distribution, which are closely related to the sample size induces void nucleation and deformation twinning mechanisms around the crack tip.
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