A Critical Evaluation of Forming Limit Curves Regarding Layout of Bending Processes

Forming limit curves (FLCs) are important to predict failure against biaxial deformation in sheet metal forming. Particularly crucial is the detection and evaluation of stable/instable transition which indicates necking ultimately leads rupture. In past, it has been observed that specific processes, particular free-form bending might not be predicted well by conventionally evaluated FLCs, i.e. Nakajima experiment, where tapered specimens stretched over a hemispherical punch until material failure. present study, FLCs from such tests notched tension (NTT) highlighting large differences between both results. The methodologies discussed with respect contact strain forming zone. three tested materials compared fracture resulting an incremental process free zone demonstrating increased prediction accuracy NTT than conventional ones. light these results, therefore encouraged critically assess application obtained NTTs various processes.