The application of some criteria for ductile fracture to the prediction of the forming limit of sheet metals

The possibility of the application of ductile fracture criteria to the formability prediction of sheet metals is examined. Some criteria in simple forms are employed and combined with the finite element simulation of sheet metal forming. From the calculated histories of stress and strain in each element, the fracture initiation site and the forming limit are predicted by means of the criteria for ductile fracture. The material constants in the criteria are determined from uniaxial and plane-strain tension tests. The calculations are carried out for the axisymmetric deep drawing of various aluminium alloy and steel sheets. A comparison between the calculated and experimental results shows that the present approach using the ductile fracture criteria gives fairly good predictions. (C) 1999 Elsevier Science S.A. All rights reserved.