Triaxial characterisation of iron powder behaviour

A complete database and constitutive laws are the key to successful computer simulations of powder compaction processes. However, the appropriate determination of material parameters that are used in mathematical models is difficult, and interpretation of scarce and often incomplete experimental data depends on the modellers. It is therefore essential to have information on powder behaviour to define accuracy and identify the limits of the model predictions. To make up for this lack of detailed information, this paper presents raw experimental data for a typical iron powder and provides information on the elastic-plastic behaviour. Useful analytical expressions of mechanical characteristics, used in most constitutive laws, are then formulated. An equation for the hydrostatic compressibility is derived as well as an equation on the critical state curve, which shows that under high pressure the plastic behaviour of the compact is the same as that of the plastic behaviour of the constituent particle material. The elasticity of compacts is also investigated showing non-linear behaviour which depends on the density and not on the mean pressure.