Applications of anisotropic yield criteria to porous sheet metal forming simulations

Macroscopic yield criteria for porous ductile sheet metals with anisotropic matrices were proposed recently. The matrix surrounding voids is assumed to follow various planar isotropic yield functions in the current study. Effects of the macroscopic porous yield criterion and the yield function of the corresponding matrix on the sheet metal under a hemispherical punch stretching operation and a cylindrical cup deep drawing operation are then investigated. Mechanisms of the void growth, void nucleation, and void coalescence are simultaneously considered here. The results of the simulation show that the macroscopic yield criterion of the porous sheet metal and the yield function of the corresponding matrix control the strain distribution and the strain localization, but not the punch force, for both operations. Early localization will be induced for the sheet with relatively small initial void volume fraction especially under the cylindrical cup deep drawing operation.