Influence of grain boundary sliding near a nanovoid on crack growth in deformed nanocrystalline materials

A theoretical model is developed that examines the effect of grain boundary (GB) sliding near a nanovoid on crack growth in deformed nanocrystalline materials. By combining complex variable method of Muskhelishvili, superposition principle of elasticity and distributed dislocation technique, the singular integral equations are solved numerically and then the stress intensity factors (SIFs) near the left crack tip are obtained. The influences of the location of the disclination dipole, the dipole arm, the orientation and the relative crack length on the SIFs near the left crack tip are evaluated in detail. The results indicate that the wedge disclination dipole produced by the GB sliding shields mode I crack tip, but anti-shields mode II crack tip. At the same time, surface stresses of the nanovoid characterized by positive surface elasticity and negative surface elasticity both show shielding effect to mode I SIFs of the crack tip, yet have negligible effect on mode II SIFs of the crack tip. Meanwhile, the mode I crack tip is more significantly shielded by the negative residual surface stresses than that of the positive residual surface stresses.