  In this work, the influence of the plastic size effect on the fracture
process of metallic materials is numerically analyzed using the strain-gradient
plasticity (SGP) theory established from the Taylor dislocation model. Since
large deformations generally occur in the vicinity of a crack, the numerical
framework of the chosen SGP theory is developed for allowing large strains and
rotations. The material model is implemented in a commercial finite element
(FE) code by a user subroutine, and crack-tip fields are evaluated thoroughly
for both infinitesimal and finite deformation theories by a boundary-layer
formulation. An extensive parametric study is conducted and differences in the
stress distributions ahead of the crack tip, as compared with conventional
plasticity, are quantified. As a consequence of the strain-gradient
contribution to the work hardening of the material, FE results show a
significant increase in the magnitude and the extent of the differences between
the stress fields of SGP and conventional plasticity theories when finite
strains are considered. Since the distance from the crack tip at which the
strain gradient significantly alters the stress field could be one order of
magnitude higher when large strains are considered, results reveal that the
plastic size effect could have important implications in the modelization of
several damage mechanisms where its influence has not yet been considered in
the literature.
