ATOMISTIC SIMULATIONS OF BRITTLE MICROCRA CK GROWTH IN ALPHA-IRON

Molecular dynamic (MD) simulations of brittle microcrack growth in mod e I show that initiation of the (001) [<(1)over bar 10>] microcrack in alpha-iron can be treated in the framework of fracture mechanics. In agreement with experimental observations, the presented fracture param eters exceed several times the Griffith values, while the maximum crac k velocity observed in MD-simulations is lower than that corresponding to the continuum prediction v(R) (Rayleigh surface waves). Microcrack growth can be described by Freund's velocity function, if the termina l velocity v(R) is replaced by the lower maximum velocity v(m). Near v (m), crack tip instabilities and branching have been observed under hi gh loading. Present results indicate that microcrack branching can be expected especially under an impact loading.