Computation of macroscopic yield surfaces by particle methods

The essential ingredient for the simulation of the cold compaction of powders by the finite element method is the provision of yield surface and ist evolution with deformation. Usually isotropic models such as the Cam-Clay- or versions of the Drucker-Prager-Cap model are used. The purpose of this contribution is to compute macroscopic yield surfaces by using particle methods. Specifically, the evolution of the yield surface including the developing anisotropy is analysed. Starting from a random aggregarte of particles, selected macroscopic deformation histories are simulated through the application of periodic boundary conditions. The prescribed particle interaction force is based on separate finite element calculations of a particle-particle indentation and two deformation histories of the aggregate are considered: An axisymmetric closed-die compaction and a non-proportional straining history involving a rotation of the principal axes of deformation.