Research on the Application of Ductile Fracture Criterion in Fracture Prediction during Sheet Metal Deep Drawing

In order to obtain the fracture strain of notched samples, the digital image correlation (DIC) technology is employed in this paper. The values of fracture-related state variables such as stress triaxiality and Lode parameter are obtained through mathematical transformation. The fracture parameters of Lou-Huh ductile fracture criterion (DFC) are calibrated by surface fitting with least square method, and the fracture curve is drawn and applied to the fracture prediction during deep drawing. The reliability of DFC is verified considering fracture stroke and location through tests. The results show that the fracture curve can predict the initiation and location of fracture successfully. Fractures are all predicted in advance under multiple blank holder force (BHF) conditions. Comparison results of finite element (FE) simulation and experiment show that the maximum error of fracture stroke is 12.9% and the fracture locations are generally consistent. The prediction of DFC is partial to safety.