Résumé
A plastic yield function for ductile materials is discussed in order to predict damage during modeling of bulk metal forming processes. The variational formulation used by Rice and Tracey [J. Mech. Phys. Solids 17 (1969) 201] is modified for a cavity in an unit cell in contact with an inclusion. Following Gurson [J. Eng. Mater. Technol. 99 (1977) 2], the influence of the plastic flow on the size and the shape of the void is analysed at the mesoscopic level. Then, the influences of the volume, of the shape of the void and the contact are introduced in a macroscopic plastic potential similar to the specific one proposed by Staub and Boyer [J. Mater. Proc. Technol. 79 (1998) 9]. This dilatational plastic potential and its corresponding plastic flow rule are implemented in a proprietary software and used for the numerical modelling of a workability test.