Modeling of localization and fracture phenomena in strain and stress space for sheet metal forming

In this study, a model based on a strain localization level to overcome the shortcomings of the well-established Forming Limit Diagram (FLD) in predicting the physical phenomenon of necking is introduced. An optical measurement system was used to capture the strain history of the Nakazima experiment until rupture occurred. In order to measure the fracture strain more accurately, a further method is introduced, which is based on the microscopic measurements of ruptured regions. This model is validated using a 3-point bending test. The results show the ability of the method to predict failure under bending conditions as well. Additionally, failure is investigated based on the pressure sensitivity and the Lode dependency. The results show that the triaxiality at the failure point is independent of the loading path.