Influence of Dislocation Pile-Up on Main Crack Propagation in Nanocrystals in the Hydrogen Environment

The influence of material micro-defects on the main crack growth under pure shear loading is studied theoretically. The mechanism behind the initiation of micro-cracks and crack propagation induced by dislocation accumulation near the grain boundary (GB) is mainly considered, and the influence of dislocation accumulation on the main crack propagation is analyzed. The research results reveal that the initiation of micro-cracks near the GB is prior to the propagation of the main crack. In a hydrogen environment, hydrogen can cause serious embrittlement of the crack tip and promote crack growth. The energy release rate in the main crack growth direction in the dislocation emission direction is the highest. Therefore, the main crack will eventually merge with the micro-cracks at the GB along the direction of the slip band, resulting in fracture of the crystal material. The research presented in this paper provides some new information for the first stage of crack propagation and contributes to the analysis of the mechanism of crystal metal fracture.