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The article addresses the problem of material fracture in metal forming processes. In the specialized literature as
well as in the available technical catalogues, it is difficult to find the values of the damage functions according to
the many available ductile fracture criteria for specific materials and specific shaping cases. Hence, experimental
studies and numerical analyses were undertaken to determine the critical values of the damage function according
to 9 ductile fracture criteria. The article undertakes to compare the values of damage functions obtained in clas-
sical calibration tests – tensile and torsion tests, under cold forming conditions. Two materials were selected for
the study, i.e. CW008A copper and S355 steel. The presented research methodology includes experimental tests
and numerical simulation carried out using Simufact. Forming v.15 software. The analysis of the obtained data
made it possible to determine the value of damage using to various criteria, including the growth and coalescence
of micro cracks (Rice&Tracey, Oyane, Argon), the initiation and development of ductile cracking in forming pro-
cesses (Freudenthal, Cockroft-Latham, Brozzo, Oh) and using extended phenomenological models based on the
history of stress triaxiality (Ayada) or the mean and equivalent stress (Zhan). The study showed that the value of
the damage function is affected by the type of calibration test, the material grade and the geometry of the samples.
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