Compaction and flow rule of oxide nanopowders

TL;DR

This paper investigates the compaction behavior of oxide nanopowders, analyzing different processes, calculating energy parameters, and proposing an alternative plastic flow rule due to the inapplicability of the associated flow rule.

Contribution

It introduces a new plastic flow rule for oxide nanopowders and provides analytical yield surface approximations, advancing theoretical understanding of nanopowder compaction.

Findings

Associated flow rule is not suitable for oxide nanopowders.

An alternative plastic flow rule is proposed.

Analytical yield surface approximations are developed.

Abstract

Transparent Al2O3 ceramics have attracted considerable interest for use in a wide range of optical, electronic and structural applications. The fabrication of these ceramics using powder metallurgy processes requires the development of theoretical approaches to the compaction of nanopowders. In this work, we investigate the compaction processes of two model granular systems imitating Al2O3 nanosized powders. System I is a loosely aggregated powder, and system II is a powder strongly inclined to agglomeration (for instance, calcined powder). The processes of isostatical (uniform), biaxial, and uniaxial compaction as well as uniaxial compaction with simultaneous shear deformation are studied. The energy parameters of compaction such as the energy change of elastic interparticle interactions and dispersion interactions, dissipative energy losses related to the processes of interparticle friction, and the total work of compaction are calculated for all the processes. The nonapplicability of the associated flow rule to the description of deformation processes of oxide nanopowders is shown and an alternative plastic flow rule is suggested. A complete system of determining the relationship of the flow including analytical approximations of yield surfaces is obtained.