Prediction of ductile fracture in metal blanking

This study is focussed on the description of ductile fracture initiation, which is needed to predict product shapes in the blanking process. Only local ductile fracture criteria are considered. The characterisation of such a model in the blanking process was considered in an earlier publication with very good results, within the experimental error. In this paper, an approach is elaborated that is less complex and thus more favourable for industrial applications. This approach incorporates the characterisation in a tensile test of a ductile fracture model that will next be applied to the blanking process. Because no existing ductile fracture model yielded satisfying results, a new criterion is proposed. This ductile fracture model is also applied on tensile tests under different hydrostatic pressure, so that the influence of triaxiality on ductile fracture could be checked. Finite element simulations and experiments for both the blanking process (five clearances) and the tensile tests under different hydrostatic pressures are performed and presented. In conclusion it can be stated that, for the investigated material, the proposed criterion yields good results within 6% of the blanking experiments over a wide range of clearances.