| A theoretical model is suggested which describes the nucleation and growth of nanocracks (nanoscale cracks) near tips of pre-existent extended cracks in fatigued nanocrystalline materials. In the framework of the model, nanocracks in fatigued nanocrystalline materials nucleate at triple junctions of grain boundaries. The enhanced nucleation and growth of triple junction nanocracks are stimulated by preceding grain boundary sliding and driven by the release of the external stresses and the stresses created by triple junction dislocations and pre-existent fatigue cracks. |
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