Abstract
In our previous studies, the limit strains of a few types of high-strength steel sheets under various strain paths from balanced biaxial to uniaxial tension were measured and compared with those derived from some criteria for ductile fracture. It turned out that the fracture strains derived from the criterion by Cockcroft and Latham gave the best fit to the experimental results. In this study, the criterion is applied to the prediction of forming limit in stretch flanging. The stretch flanging tests of a high-strength steel sheet are simulated by the dynamic explicit finite element program LS-DYNA ver. 971 with shell elements. The comparison of the simulated results with the experimental results shows that the forming limit in stretch flanging is successfully predictable by the present approach when the work hardening and damage of the sheet edge in the blanking process are taken into consideration.