Prediction of Forming Limit of High-Strength Steel Sheets by Means of Criterion for Ductile Fracture

摘要

In this study, first, the forming limit diagrams of a few types of high-strength steel sheets are experimentally examined. And they are compared with those derived from some criteria for ductile fracture. It is found that the criterion proposed by Cockcroft and Latham can give the forming limit diagram appropriate to the high-strength steel sheets, including the effect of the normal anisotropy. Next, the ductile fracture criterion is combined with the finite element simulation of sheet forming processes. Calculations are carried out for cylindrical deep drawing of the high-strength steel sheets. The comparison between the numerical and experimental results demonstrates that the critical punch stroke at the fracture initiation and the limiting drawing ratio are successfully predicted by the present approach.