Density and plastic strain evaluations using small-angle X-ray scattering and finite element simulations for powder compacts of complex shape

Previous work suggested that two-dimensional small-angle X-ray scattering (2D-SAXS) could offer a new method for evaluating the local variations of density, strain and principal strain direction within powder compacts, which arise due to the effects of friction and die shape. In order to test this method further, this work compared results from 2D-SAXS with finite element (FE) simulations using a modified density-dependent Drucker-Prager Cap (DPC) model, for compacts of complex shape, prepared using a cylindrical die, a flat-faced upper punch and shaped lower punches with three different central protrusions. Variations in compaction behaviour were observed, which were due to friction against the die walls and the punch shape. Good agreement was obtained between SAXS measurements and FE simulation, supporting previous indications. Hence, this combination of experimental and computational techniques appeared particularly powerful for investigating powder compaction behaviour, in considerable accuracy and detail. Moreover, observations of the compaction behaviour in the vicinity of the central protrusion may be relevant to tablets with embossed features or compacted artefacts of more complex shape.