Akademik Veri Yönetim Sistemi
POWDER TECHNOLOGY, cilt.89, sa.3, ss.239-254, 1996 (SCI-Expanded)
This paper is concerned with the internal form of compacted ceramic green components. The structural inhomogeneity of alumina specimens, compressed in a top pressed cylindrical die, is studied experimentally, by using lead balls as tracers to detect the densification, as well as by numerical computation. The flow behaviour of a ceramic powder, an agglomerated alumina, is described by the modified Drucker-Prager/cap elasto-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 selecting the necessary material parameters by the inclusion of material response data and assumptions made in the implementation of the numerical model are described. The accuracy of the presented numerical method is evaluated by comparing the simulation results with experimental data obtained from density measurements. The evolution of the density distributions during the entire compaction process is predicted. The determining step for the formation of the subtle density variations on the central axis of the green ceramic compacts was found, from the modified Drucker-Prager/cap finite element analysis, to be the unloading step of the compaction process. In this respect, a comparison of the finite element and experimental results showed good mutual agreement.