Forming Limit Prediction in Bore Expansion by Combination of Finite Element Simulation and Ductile Fracture Criterion

Abstract

The bore expansion tests of a mild steel sheet and two types of high-strength steel sheets using conical- and flat-headed punches are simulated using the dynamic explicit finite element program LS-DYNA ver. 970 with shell elements. The ductile fracture criterion proposed by Cockcroft and Latham is applied to the prediction of the forming limit in bore expansion processes. In our previous studies, the fracture strains derived from the criterion gave the best fit to the experimental results in biaxial stretching. The comparison of the simulation results with the experimental results in this study shows the possibility of forming limit prediction via the present approach in which we take the work hardening and damage in the blanking process of the bore into consideration.