D2.1 Fracture model to describe the energy dissipation during crack propagation at low and high deformation rates – Abstract

On the modeling and simulation frame work, the fracture study started by the edge cracking problem. It occurs on the steel sheets edges during forming operation and crash impacts. The simulation has been initiated by adapting the ductile damage model implemented in the commercial software ABAQUS. A methodology has been developed to obtain the damage initiation and the damage evolution laws. This methodology uses the simulation adjustment to the double notch test specimens (DENT) which are used to determine the essential work of fracture.

It is hypothesized that there is a direct relationship between the essential work of fracture and the damage model, especially with the damage evolution function. Although it has not been proven, it has been shown a relationship between fracture work of different specimens with different ligaments and the area in the damage evolution diagram.

An empirical approach has been used to adjust the model to finite elements meshes with shell elements of 1 mm minimum length. Considering that it is difficult to further refine the mesh in real component analysis.
A first validation was performed using the Half Specimen Dome Test (HSDT) results and the behavior was compared using models based on FLD and FLD combined with ductile damage on the edge related with the essential work of fracture. The best results are associated with the behavior of small ligament on DENT specimens. The ductile damage predicts the edge cracking while the FLD does not have this capability.
The material used in the adjustment has been ArcelorMittal Fortiform steel with a thickness of 1.4 mm. A DP980 from the same steel maker has also been tested with good results.
As future work, the behavior of the model and the methodology with other steels and with other forming operations and impact behavior must be explored.