  In this paper, the dilatational response of porous solids with
pressure-insensitive matrix displaying strength differential (SD) effects is
investigated. To this end, micromechanical finite-element analyses of
three-dimensional unit cells are carried out. The matrix behavior is governed
by the isotropic form of Cazacu et al. (2006) criterion that accounts for SD
effects through a parameter k. Simulation results are presented for
axisymmetric tensile loadings corresponding to fixed values of the stress
triaxiality for the two possible values of the Lode parameter, LP. For moderate
and high stress triaxialities, it is shown that for materials for which the
matrix tensile strength is larger than its compressive strength (k > 0), under
tensile loadings corresponding at LP=1 the void growth rate is much faster than
in the case of tensile loadings at LP=-1. The opposite holds true for materials
with matrix tensile strength lower than its compressive strength (k< 0). This
drastic difference in porosity evolution is explained by the distribution of
the local plastic strain and stresses, which are markedly different than in a
von Mises material (i.e. no SD effects of the matrix).
