Constitutive modelling of powder compaction – I. Theoretical concepts

In this paper we examine the structure of constitutive laws for the compaction of metal powders. Incremental and deformation theory models are examined. It is argued that for practical processing schedules a deformation type theory is capable of representing the material response. A model for stage 1 compaction is presented and surfaces of constant complementary work density are plotted in Kirchhoff stress space. The theoretical concepts are employed in an accompanying paper to guide the interpretation of experimental data.