Effect of single-crystal plastic deformation mechanisms on the dilatational plastic response of porous polycrystals

In this paper, the combined effects of texture and asymmetric single-crystal plastic deformation mechanisms on the dilatational response of voided polycrystals are assessed for the first time. To this end, a full-field dilatational viscoplastic Fast Fourier Transform (FFT)-based approach is used to generate gauge surfaces for porous polycrystals deforming by twinning at single crystal level, which are compared to yield surfaces obtained according to a recent analytical criterion for porous materials. Both approaches are cross-validated, revealing unusual features of the dilatational response, namely, a lack of symmetry of the surfaces with respect to both the hydrostatic and deviatoric axes. This strong sensitivity to the third invariant of the stress deviator is associated to the anisotropy and the tension-compression asymmetry of the plastic response of the matrix. (C) 2012 Elsevier Ltd. All rights reserved.