A new yield function for compressible materials

Yield behaviour of cold compacted composite powders

“…According to their theory, the pressure P required to densify the compact from an initial relative density D 0 to a relative density D is given by Predicted e ect of strain path on the evolution of the yield surface [10]. f is the ratio of the tensile cohesive strength to the compressive strength at the particle contact, and p y is the hydrostatic yield strength of the compact as given by equation (1).…”

“…A number of compaction models for the rateindependent densi®cation of porous materials have been reviewed by Doraivelu et al [1]. These models assume an elliptical yield surface in deviatoric stress vs mean stress space, and are calibrated against a limited set of experimental data.…”

“…These models assume an elliptical yield surface in deviatoric stress vs mean stress space, and are calibrated against a limited set of experimental data. Doraivelu et al [1] and Kuhn and Downey [2] calibrated their models using uniaxial unconstrained compression tests on sintered aluminium alloy. Kim et al [3] conducted combined tension±torsion tests on sintered iron specimens for the calibration of their yield function.…”

Compression mechanics of granule beds: A combined finite/discrete element study

“…We assume an elliptic yield function of the form proposed by Doraivelu et al (1984) and Oliver et al (1996),…”

“…The purpose of this work is to extend this procedure to more realistic plastically deforming granules. To this end, we first describe an appropriate constitutive model for the granule behaviour, based on the elliptic yield surface proposed by Doraivelu et al (1984) and Oliver et al (1996), which allows porous particles to both deform and to densify plastically, whereas only volume-preserving plastic deformation is possible for nonporous ones. The reason for introducing this rather elaborate model is that porous granules often are encountered in pharmaceutical applications.…”