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 discret e dislocation dynamics and cohesive surfaces. A two-dimensional analysis is carried out with the dislocations all of edge character and modeled as lin e singularities in an elastic material. At each stage of loading, superposi tion is used to represent the solution in terms of solutions for edge dislo cations in a half-space and a complementary solution that enforces the boun dary conditions. The latter is non-singular and obtained from a finite elem ent solution. The lattice resistance to dislocation motion, dislocation nuc leation, dislocation interaction with obstacles and dislocation annihilatio n 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 representativ e of aluminum are employed. This study focuses on the influence of dislocat ion nucleation rate and loading rate on the course of crack growth. (C) 200 1 Elsevier Science B.V. All rights reserved.