A constitutive model for compaction of granular media, with account for deformation induced anisotropy
✍ Scribed by Jan Brandt; Larsgunnar Nilsson
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 312 KB
- Volume
- 4
- Category
- Article
- ISSN
- 1082-5010
No coin nor oath required. For personal study only.
✦ Synopsis
A constitutive model is proposed for the cold compaction of metal powders. It relies on classical concepts for elasto-plastic materials. For cemented carbides, which is the current application of the model, it is shown by experimental data that there develops signi"cant anisotropy during a non-isostatic compaction. The model encompasses anisotropy through a kinematic hardening mechanism. For a certain state of hardening the back stress magnitude depends on the mean stress, such that there is a rotation (around the origin) of the yield surface. The need for a two-dimensional hardening parameter set, the relative density and a measure of the intensity of the anisotropy, is demonstrated. A compactness tensor P that holds the current relative density as det(P) and the directionality of the compaction history is conceived. The #ow direction is derivable from a non-associated #ow potential, but is more easily represented as the ratio of magnitude of deviatoric plastic increment to magnitude of volumetric plastic increment. The basic assumption of a #ow potential is needed only to establish the form of the deviatoric #ow component. Various functions of the model are mapped by series expansions from irregularly spaced experimental data in the sense of leastsquare "ts.