Paper number 315

EFFECTIVE PROPERTIES 0F NON-LINEAR ORTHOTROPIC POROUS-DUCTILE MATERIALS

Stefano Mariani and Alberto Corigliano

Department of Structural Engineering, Politecnico of Milano
Piazzo Leonardo da Vinci 32
20133, Milan, ITALY

Summary

Effective properties of non-linear, elastoplastic two-phase composites are here developed in the particular case of a vacuous inclusion embedded in a ductile metal matrix. The constitutive behavīour of the porous-ductile medium is here described by means of an instantaneous yield criterion which bounds the elastic domain and is a function of the current microstructural geometry, and by means of evolution laws for the internal state variables that are assumed to characterize the microstructure of the single Representative Volume Element (RVE). In order to derive the homogenized material behaviour of the orthotropic two-phase composite, the kinematic approach of limit analysis is applied to a cylindrical RVE with elliptic cross-section containing a coaxial and confocal elliptic cavity. The influence of the microstructure evolution, represented by the development of plastic-strain induced anisotropy and void growth, on the effective response of the RVE is discussed and compared to the avalaible results which are based on the transversely isotropic Gurson's model. Specific attention is here devoted to loading conditions with principal stress and strain-rate directions aligned with the principal axes of the RVE geometry, in order to rule out the effect induced by plastic spin (and related co-rotational objective derivatives) on the material behaviour.

Keywords

effective properties, micromechanics, plasticity, anisotropy, porous media, voids, metal matrix composite.