Analysis of the effect of a micro-crack on plastic zone of the edge macro-crack tip by macroscopic and microscopic methods

The effect of the micro-crack on plastic zone ahead of the macro-crack tip (PZMA) is analyzed based on macroscopic and microscopic methods. From the macroscopic perspective, the plastic deformation is due to the local stress near crack tip is more than the yielding limit. So the complete stress field is calculated based on the distributed dislocation technique (DDT) and the plastic zone (PZ) is determined by von Mises yielding criterion (MYC). On the other hand, the crack tip plasticity is simulated by finite element method (FEM). From the microscopic perspective, the plastic deformation is caused by dislocations emitted from crack tip. So PZ is represented by dislocations, and it is determined based on DDT and dislocation-free zone (DFZ) model. The results show the micro-crack located in front of PZMA has the amplifying effect on PZMA. PZMA is separated by the micro-crack located in PZMA. The micro-crack behind PZMA has no effect on PZMA. PZMA has the shielding effect on the macro-crack propagation, and the shielding effect increases with PZMA increasing. The micro-crack has the amplifying effect on PZMA at about x(0)/a > 0.5, while it has the shielding effect at about x(0)/a < 0.5. These results are useful for predicting and interpreting the plastic behaviors at the crack tip.