  In this work a general framework for damage and fracture assessment including
the effect of strain gradients is provided. Both mechanism-based and
phenomenological strain gradient plasticity (SGP) theories are implemented
numerically using finite deformation theory and crack tip fields are
investigated. Differences and similarities between the two approaches within
continuum SGP modeling are highlighted and discussed. Local strain hardening
promoted by geometrically necessary dislocations (GNDs) in the vicinity of the
crack leads to much higher stresses, relative to classical plasticity
predictions. These differences increase significantly when large strains are
taken into account, as a consequence of the contribution of strain gradients to
the work hardening of the material. The magnitude of stress elevation at the
crack tip and the distance ahead of the crack where GNDs significantly alter
the stress distributions are quantified. The SGP dominated zone extends over
meaningful physical lengths that could embrace the critical distance of several
damage mechanisms, being particularly relevant for hydrogen assisted cracking
models. A major role of a certain length parameter is observed in the multiple
parameter version of the phenomenological SGP theory. Since this also dominates
the mechanics of indentation testing, results suggest that length parameters
characteristic of mode I fracture should be inferred from nanoindentation.
