Effects of Damage Evolution on Edge Crack Sensitivity in Dual-Phase Steels

The present study aims to thoroughly investigate the edge-cracking phenomenon in high-strength sheets. Hence, the edge crack sensitivity of three dual-phase steels is studied in various combinations of edge manufacturing and forming processes. Finite element simulations are performed to elaborate the study. In this regard, the Yoshida–Uemori kinematic hardening model is employed to describe the plasticity behavior of the materials under multistep processes. A stress-state fracture model is coupled with this plasticity model to illustrate the distinguished local fracture strains of each material. Moreover, the effects of strain rate and the consequent temperature rise on hardening and damage are taken into account, which play significant roles during shear-cutting. The results show that although the shear-cutting processes are applied at very low speed, the strain rate and induced temperature are still high at the cutting area. The hole expansion results show different fracture behaviors for different cases. In brief, cracking is initiated at a location, which shows the highest damage accumulation during edge manufacturing plus the subsequent forming process. Such a complicated situation can only be successfully predicted by using a computer-aided approach along with proper material modeling, like the applied model in this study.