A workability criterion for internal ductile fracture in the steel cold heading process

A new technique to set a workability criterion for predicting the limits for internal ductile fracture in cold-headed steel parts, is discussed. The methodology to determine the material parameters for the workability criterion, consist of the drop weight compression test (DWCT) to stimulate the cold heading process (CHP) in conjunction with finite element analysis. It was found that the presence of second phases (MnSinclusions, martensite) plays an important role in voids and crack initiation under compressive triaxial stress. Oyane Criterion, which is based on the damage estimated by the history of the equivalent plastic strain and stress triaxiality, is found to be applicable to predict internal ductile fracture in CHP.