Deformation inhomogeneity at the crack tip of polycrystalline copper

Molecular dynamics simulation is conducted on single crystal and polycrystalline copper. Two different crack tip orientations (001) [-110] and (001) [010] are selected for copper single crystal. For copper single crystal with crack tip orientation of (001) [010], stress is concentrated at the crack tip, and cleavage crack propagation happens due to lack of dislocation activity at the crack tip. For copper single crystal with crack tip orientation of (001) [-110], continuous emission of dislocations from crack tip results crack tip blunting and reduction of stress concentration as well. Homogeneous crack tip stress and strain fields are evident for copper single crystals, however, stress and strain fields slightly alter with the generation of dislocations and defects. Crack tip stress and strain distribution are inhomogeneous from the beginning of the deformation for polycrystalline copper. Higher stress concentration at the grain boundary than crack tip results in nucleation of initial dislocations from the grain boundary during plastic deformation.

Automated summary

The study found that different crack tip orientations in single crystal copper lead to different dislocation activities and crack propagation modes, while the crack tip stress and strain distributions are uneven in polycrystalline copper, with stress concentration at grain boundaries resulting in the formation of dislocations.