A finite-element approach for the shape prediction of ceramic compacts during sintering

Abstract

This paper describes and demonstrates the effectiveness of a finite-element procedure to predict the shape changes of "green powder compacts" during sintering processes. The approach is based on the conservation-of-mass principle and requires for its implementation (i) descriptions of the finite-element meshes of the original form (powder bed) and the green bodies when ejected from the die (thus, descriptions of the geometries of the compact before and after the compaction process) and (ii) the densities of the compacts before the compaction and after the sintering processes. Numerical shape predictions have been compared with experimental data, for all the external surfaces that are obtained from sintered, cylindrical alumina specimens. The overall predicted diametric dimensional-variation changes correlate with the corresponding measured data; both indicate a "barrel" shape, The comparisons reveal that the quantitative predictions in regard to the height and diameter range correlate closely with the measured values; the differences are <1.6% and 0.4%-0.08%, respectively. The overall predicted deviation changes of the end surfaces of the sintered compacts correlate,vith the corresponding measured data; both indicate a "concave" shape, with reference to the horizontal plane, as viewed from the compaction direction. The quantitative shape comparisons for the top and bottom surfaces are <18.9% and <65.84%, respectively. The qualitative predictions at the top and bottom surfaces are considered to be in good agreement, for most practical purposes.