Mode I crack tip plastic zone,dislocation-free zone and their effects on crack propagation

Edge dislocation emissions from a Mode I crack tip along multiple inclined slip planes are simulated,and plastic zones as well as dislocation-free zones are obtained.It is found that the shape of the mode I plastic zone is similar to that obtained by von Mises or Tresca yielding criterion but leaning forward from the crack tip.The shape of dislocation-free zone is similar to that of plastic zone.With dislocation emission,the plastic zone becomes larger and larger while the dislocation-free zone is getting smaller and smaller.Judged by the strain energy density factor,the crack propagation potential decreases remarkably with dislocation emission.When a clear dislocation-free zone exists,the crack potential propagation direction will keep along the crack surface.However,when the plastic zone is fully developed or the dislocation-free zone is vanished,the crack potential propagation direction may also be changed.