Two-dimensional discrete dislocation simulations of the crack-tip plasticity of a macrocrack-micro-crack system representing the fracture behavior in ferritic steels were presented. The crack-tip plastic zones were represented as arrays of discrete dislocations emitted from crack-tip sources and equilibrated against the friction stress. The dislocation arrays modify the elastic field of the crack; the resulting field described the elastoplastic crack field. The simulated crack system involved a micro-crack in the plastic zone of the macro-crack (elastoplastic stress field). The effects of the crack-tip blunting of the macro-crack were included in the simulations; as dislocations were emitted, the micro-crack was kept at a constant distance from the blunted tip of the macro-crack. The brittle-ductile transition curve was obtained by simulating the fracture toughness at various temperatures. A consideration of the effects of blunting was found to be critical in predicting the sharp upturn of the brittle-ductile transition curve. The obtained results were compared with existing experimental data and were found to be in reasonable agreement.

Dislocation Simulation of Brittle-Ductile Transition in Ferritic Steels. S.J.Noronha, N.M.Ghoniem: Metallurgical and Materials Transactions A, 2006, 37[3], 539-44