Assessment of ductile fracture criteria with respect to their application in the modeling of cross wedge rolling

Ductile fracture is a common failure mode in cross wedge rolling (CWR) and can be predicted by analyzing material damage functions. This paper describes 10 such functions. To determine the moment of fracture, one must know the critical damage function which is calculated via calibration test. It is vital to ensure that the stress state during calibration is as close as possible to the real stress. Since there are no calibration tests dedicated to cross rolling processes, a new test has been devised, based on a rotary compression process for cylindrical samples. Using the proposed calibration test and 10 fracture criteria, the critical damage values of C45 steel deformed at 1150 °C are determined. Next, CWR tests are performed using technological parameters conducive to crack formation in the axial region of the formed step on the workpiece. Numerical and experimental results of the moment of crack initiation and its length are compared, and – as a result – 4 damage criteria that best predict material fracture are selected.