A discrete dislocation analysis of rate effects on mode I crack growth

The mesoscopic growth of a crack in an elastic-plastic single crystal under mode I loading conditions is studied using a formulation involving discrete dislocation dynamics and cohesive surfaces. A two-dimensional analysis is carried out with the dislocations all of edge character and modeled as line singularities in an elastic material. At each stage of loading, superposition is used to represent the solution in terms of solutions for edge dislocations in a half-space and a complementary solution that enforces the boundary conditions. The latter is non-singular and obtained from a finite element solution. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and dislocation annihilation are incorporated into the formulation through a set of constitutive rules. The cohesive surface methodology allows crack growth to emerge naturally from the boundary value problem solution. Material parameters representative of aluminum are employed. This study focuses on the influence of dislocation nucleation rate and loading rate on the course of crack growth. (C) 2001 Elsevier Science B.V. All rights reserved.