THE INTERNAL FORM OF COMPACTED CERAMIC COMPONENTS - A COMPARISON OF AFINITE-ELEMENT MODELING WITH EXPERIMENT

This paper is concerned with the internal form of compacted ceramic gr een components. The structural inhomogeneity of alumina specimens, com pressed in a top pressed cylindrical die, is studied experimentally, b y using lead balls as tracers to detect the densification, as well as by numerical computation. The flow behaviour of a ceramic powder, an a gglomerated alumina, is described by the modified Drucker-Prager/cap e lasto-plasticity material model developed for powder applications. The modified Drucker-Prager/cap constitutive model, implemented by using the finite element code ABAQUS, is discussed. The procedure for select ing the necessary material parameters by the inclusion of material res ponse data and assumptions made in the implementation of the numerical model are described. The accuracy of the presented numerical method i s evaluated by comparing the simulation results with experimental data obtained from density measurements. The evolution of the density dist ributions during the entire compaction process is predicted. The deter mining step for the formation of the subtle density variations on the central axis of the green ceramic compacts was found, from the modifie d Drucker-Prager/cap finite element analysis, to be the unloading step of the compaction process. In this respect, a comparison of the finit e element and experimental results showed good mutual agreement.