Improved ductile fracture criterion for cold forming of spheroidised steel

This paper presents some of the criteria commonly used to predict ductile fracture in metal-forming operations. To examine the adequacy of these criteria, the test data of spheroidised steel are considered. A simple ductile fracture criterion is proposed in terms of integrals of stress functions. This criterion takes into account the tensile stress ratio and triaxiality. A simple and reliable procedure is also suggested to evaluate the material constants in the criterion. It is found that the proposed ductile fracture model correlates the test data of spheroidised steel.