Multiscale modeling of the brittle to ductile transition

A recently introduced method of crack representation as a distribution of three-dimensional Volterra dislocations is used in conjunction with two-dimensional dislocation dynamics simulations to study the brittle to ductile transition behavior of Ferritic Steels. The crack-tip plasticity zone is represented as an array of discrete dislocations emitted from crack-tip sources. The dislocations shield the crack and result in an increase of the applied stress intensity for fracture from the pure Griffith value. The crack system responsible for fracture in Ferritic Steels is modeled by a macrocrack and a microcrack in its field. Crack-tip plasticity of microcrack is also modeled by arrays of emitted dislocations. The simulations are performed for different friction stresses corresponding to different yield stresses or temperatures. The brittle to ductile transition fracture toughness curve is obtained and compared to experiments.