TABLE OF CONTENTS Three-dimensional Prediction of Cavity Growth in Finite Transformations
Cyril Bordreuil, Jean-Claude Boyer and Emmanuelle Sall
Laboratoire de M anique des Solides, Insa de Lyon, Villeurbanne, France
The prediction of void growth during the metal forming process is of concern for the reliability of safety parts. Classical potentials for porous materials exist for empty voids, as for the Gurson-Tvergaard yield surface [GUR 77], and underestimate the plastic dilatation under loading with a triaxiality ratio ( ? m / ? 0) of less than 1.5. Few works, dealing with ductile damage, take into account the presence of an inclusion in a void, at the macroscopic level, during large plastic straining. In this paper, a specific plastic potential, fulfilling the mass balance, and including new improvements based on a three-dimensional void growth law is proposed. The development of the present model follows previous work [BOR 01] where the influence of inclusion in voids on damage change has been shown. The shape of the defect is assumed to be aproximated by an ellipsoid, the spin of which as well as the rate of its radii are calculated for the damage change with or without internal inclusion. The real orthotropic behaviour is modelled with special attention to frame indifference.
The geometry of an ellipsoid is defined by the radii of its semi-axes, the orientation in a selected frame, and its center chosen at the center of the frame, for the sake of simplicity. The set of the...
