Fig. The load-displacement curve for asymmetrically notched specimen
5.4 Double notched specimen
A benchmark simulation has been performed in order to assess the robustness of the computations for different critical equivalent plastic strain. Motivated by the blanking process, a problem geometry with two asymmetrically placed rounded notches is used for this purpose.54 The geometry and boundary conditions are given in Table 3-V. Vertical displacements are imposed on the top and left boundaries, while horizontal displacements have been prevented. The bottom and right boundaries are remained fixed. The material parameters are those of Material III in Table 1. The adopted discretization contains 13240 quadrilateral elements with mesh refinement in the expected crack propagation region.
In this illustrative example, the damage fields aren’t quite smooth. The tensile loading causes the development of a plastic shear band between the two notches and gives rise to damage initiation at the notches. In the context of ductile fracture, the same problem has been addressed using a non-local damage model for the initial continuum damage phase, followed by a discontinuous crack propagation phase predicted through a remeshing strategy.54 Results showed the development of a plastic shear band diagonally across the specimen, which in turn results in a curved crack trajectory which initiates at both the notches and propagates towards the center of the specimen where the two crack branches merge, Fig.10. It is worth noting that, with the increasing critical plastic strain, secondary cracks initiate at the surface of the top and bottom boundaries and start to propagate to the other side.