Abstract
Evaluation of delayed fracture property is one of the major barriers for application of high strength steel sheet to automotive parts. We are proposing a delayed fracture evaluation method using four-point bending test piece. In this study, we reported that it was possible to investigate the maximum unfractured stress of steel sheets with shear edge by using four-point bending specimen. In addition, it was clarified that the shear clearance and shear angle, which were shear conditions, greatly affected the delayed fracture resistance of steel sheets. The reason for the change in the delayed fracture resistances was estimated to be the change in the amount of the dislocation, vacancy or residual stress at shear edge of steel sheets by the shear condition.
