Size effects in ductile failure of porous materials containing two populations of voids

The ductile failure behavior of porous materials containing two populations of voids of different size is investigated numerically by means of 3D cell model calculations. In contrast to previous studies a non-local Gurson model is used to describe the secondary void population in the matrix material. Due to the internal length scale incorporated in the non-local model, it is possible to describe the size of the secondary voids in the matrix material. The results are obtained for loading states with different stress triaxialities and Lode parameters. The influence of the size of the secondary voids is analyzed and it is shown that larger secondary voids lead to a higher stress carrying capacity. This size effect is studied for different primary void arrangements. Furthermore, the strain and primary void volume fraction at the onset of coalescence are presented and cross references to experimental findings are drawn.