Homogenisation of elasto-plastic open-celled foams

The effective yield behaviour of open-celled metal foams is studied by a micro-mechanical model. As a surrogate model for the sponge-like microstructure the simplified Kelvin foam is used. The yield loci in strain space and stress space are constructed by conducting numerical experiments. For the determination of the effective stresses a strain-energy based homogenisation procedure is adopted. The numerical examples show that the initial yield surface in the normal strain space is similar to a polyhedron with sharp corners. The further evolution of the yield surface is characterized by kinematic and isotropic hardening effects. In addition, the stress yield surface may rotate under certain loading conditions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)