Mode I and mode II stress intensity factors and dislocation density behaviour in strain gradient plasticity

In this study, we use the mechanism-based strain gradient plasticity theory to evaluate both crack tip dislocation density behaviour and coupled effect of material plastic properties intrinsic length on non-linear amplitude factors. The two planar classical stress–strain states are examined, namely, plane stress, under pure mode I II loading conditions. constitutive relations based Taylor’s model, which enables gaining insights into role increased associated with large gradients in near cracks. model is implemented a commercial finite element (FE) software package using user subroutine, nonlinear stress intensity factors (SIF) evaluated as function length, characterising scale at effects become significant. As result FE calculations distributions, fracture state determined. I, geometrically necessary (GND) located symmetrically respect blunted tip. On contrary, II, GND becomes concentrated sharp parts case, initiation shown be likely occur region tip, where triaxiality their maximum. relation between equilibrium densities well SIF work hardening exponent discussed.