Molecular dynamics simulation of fatigue crack propagation in bcc iron under cyclic loading

The mechanism of crack propagation under cyclic loading in iron single crystal was investigated using molecular dynamics simulation. The cyclic loading was strain controlled and three typical specimens of pre-existing center crack of [001](010), [0 0 (1) over bar -1](110) and [1 1 (2) over bar](1 1 1) models were chosen to study the effect of orientation on fatigue crack propagation. The slip bands, vacancies and voids nucleation were observed during the process of crack growth under cyclic loading, the rate of crack growth and slip direction were different for the three models. No significant slip band was observed in [1 1 2](111) model, and the crack propagation was brittleness. In addition, the influences of grain boundary on crack growth were analyzed on Sigma 3 < 1 1 2 >{1 1 1} and Sigma 5 < 310 >{001} models. No significant effect was observed for Sigma 3 on crack propagation, while Sigma 5 resisted crack growth remarkably and resulted in a decreasing rate of crack growth, during which a little hexagonal close-packed (hcp) slip bands appeared in the plastic deformation zone. (C) 2014 Elsevier Ltd. All rights reserved.