Molecular Dynamics Simulation of Brittle Fracture in Bcc Iron

Crack propagation in bcc iron at different strains under low temperature (30K) has been studied using the atomistic simulation. We show that cracks display a brittle character of extension at low strains, and at relative higher strains cracks extend with a periodic series of twins(or SF) bursts. These bursts decrease the crack speed and produce velocity oscillations with an increase in energy dissipation that increases the toughness. Here we also develop a new form of dynamic fracture energy. Using our form of dynamic fracture energy, the results therefore are in quantitative agreement with the theoretical single-crack equation of motion.