Constitutive modelling of powder compaction – II. Evaluation of material data

The structure of constitutive laws for powder compaction is examined in a companion paper, where a suitable framework for incremental and deformation theory models is developed. In this paper the response of a commercial steel powder is investigated using triaxial compaction experiments. The tests were designed to critically evaluate the underlying assumptions of the two modelling approaches and to calibrate and validate the models. It is demonstrated that for loading histories that are characteristic of industrial die compaction processes, a deformation plasticity model is capable of describing the material response, while the incremental plasticity response is very sensitive to the detailed form of the model in the early stages of compaction, where the material has a very low yield stress and undergoes large deformations without being able to sustain a sizeable load.