Gurson-Cohesive modeling (GCM) for 3D ductile fracture simulation

A Gurson-Cohesive Model (GCM) is proposed to investigate 3D ductile fracture accounting for the void growth, coalescence, and complete failure phenomena. The proposed model idealizes the ductile fracture process as continuum damage evolution, cohesive crack initiation, nonlinear softening along the crack surface, and complete failure. The Gurson model is employed to describe continuum damage with void growth, while the cohesive zone model is utilized to introduce discontinuous cracks and represent nonlinear softening behavior along the crack surfaces. The transition from the continuum damage to discontinuous crack is taken into account systematically using a porosity-based crack initiation criterion considering stress triaxiality. The computational results successfully reproduced the experimental results of fracture tests with 15-5 PH steel and structural carbon steel 20 within the unified modeling framework. Furthermore, strong and stable convergence of global and local responses (e.g., load-displacement curve, area reduction, crack tip location) are demonstrated under the mesh refinement without the aid of any ad hoc characteristic length scale parameter in the simulations.