DISCRETE DISLOCATION SIMULATIONS AND SIZE-DEPENDENT HARDENING IN SINGLE SLIP

Plastic deformation in two-dimensional monophase and composite materia ls is studied using a discrete dislocation dynamics method. In this me thod, dislocations are represented by line defects in a linear elastic medium, and their interactions with boundaries or second-phase elasti c particles are incorporated through a complementary finite element so lution. The formulation includes a set of simple constitutive rules to model the lattice resistance to dislocation glide, as well as the gen eration, annihilation and pinning of dislocations at point obstacles. The focus is on the predicted strain hardening of these materials when only a single slip system is active. When the particle morphology is such as to require geometrically necessary dislocations, hardening in the composite materials exhibits a distinct size effect. This size eff ect is weaker than that predicted by simple analytical estimates based on geometrically necessary dislocations.