Evaluation of Ductile Fracture Criteria in Cold Forging of Hollow Parts

Abstract

In the present study, the ductile fracture behavior occurring during the cold forging of hollow parts was tested under various back-pressure force conditions. From the experimental result, it was found that the position and direction of ductile fracture can be changed in accordance with the applied back-pressure force. Numerical simulations were carried out to determine the appropriate ductile fracture criteria. The inverse calculation technique was applied to improve the simulation accuracy, adjusting the flow stress data. Two types of ductile fracture model, the traditional Cockcroft-Latham model and its modification, were evaluated. In the modified model, the damage value was selected from among several damage values calculated using stress and strain components transferred to different directions. From the result, the modified ductile fracture model predicted the ductile fracture behavior more accurately compared with the traditional Cockcroft-Latham model.