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In this paper, a constitutive modeling of the metal powder compaction is presented as a first step of ongoing research of a multiscale and multistage mathematical based model concept for powder metallurgy component design and performance prediction using the finite element method. In recent years, techniques such as finite element analysis have received wide attention for their high applicability to powder metallurgy (PM) industry. These techniques provide a valuable tool in predicting density and stress distributions in the pressed compact prior to the actual tooling design and manufacturing process. However, the accuracy of FE prediction highly depends on the possibility to obtain appropriate experimental data to calibrate and validate the powder material model. Within the framework of continuum mechanics, the plasticity model depends on external and internal state variables such as temperature, stress, hardening, relative density and contact between metal powder particles.

Torsional softening arising from the deformation-induced anisotropy of texture and dislocation substructure formation affects various regions of the forming limit diagram. The third invariant of overstress, is included in the kinematic and isotropic hardening equations to reflect the dislocation substructure and texture effect on the torsional softening for 304L stainless steel. Common J2 type theories that do not model the torsional softening exhibited in effective stress-strain curves of compression and torsion give rise to different responses at localization and failure and in the post-localization regime.

An internal state variable plasticity/damage model was employed in explicit and implicit finite element codes to predict forming limit diagrams. The finite element analyses showed that either the explicit or implicit methods can be used to determine sheet metal thickness effects, temperature and rate effects, and loading history effects. A novel way of introducing instability was introduced by different initial void volume fractions in neighboring materials. Shell elements can be used to shorten cpu times, given that shell bending assumptions are not violated.