Asymmetrical propagation mechanism of the crack in bcc iron

ZF Zhao and ZY Qin and FL Chu, COMPUTATIONAL MATERIALS SCIENCE, 172, 109341 (2020).

DOI: 10.1016/j.commatsci.2019.109341

This work investigates the asymmetrical propagation mechanism of the crack in bcc iron by carrying out molecular dynamics simulations and stress analysis. The results show that slip characteristics of the atoms on both sides of the same crack tip are different due to the asymmetrical atomic distribution. Since atoms always tend to slip on the slip system with less resistance, slip band can only be observed on one side of the crack tip during crack propagation. The crack propagation behavior is asymmetrical. Normal and Mises stresses are found to be concentrated on slip plane, especially near the crack tip and in front of the slip band. The stress concentration near the crack tip can lead to an increase in slip band layer, and then can result in a transformation from stacking fault to twinning. However, the stress concentration in front of the slip band can lead to the slip band expansion along the slip direction. Besides, the results also show that crack will cleave along the original direction on the original plane under normal stress if the original plane is cleavable or else it will cleave along the new direction on the new cleavage plane with lowest critical Griffith stress intensity factor under the X and Y components of atomic stress.

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