Determination of material constants and prediction of fracture in sintering of ceramic products

Methods of determining material constants required for finite element simulation of sintering of ceramic green bodies are proposed. The flow stress and shrinkage strain-rate in sintering are measured from a simple compression test with a constant load. The critical difference in volumetric strain in the criterion for sintering fracture is determined from a three-point bending test with a constant load. Using the measured material constants, the densification behaviour in compaction and sintering processes of circular tiles composed of a coloured upper layer and uncoloured substrate with a groove is simulated by the viscoplastic finite element method. The occurrence of sintering fracture is predicted from the difference of volumetric strain calculated by the finite element simulation. The accuracy of the calculated results is improved by using the flow stress with strain-rate and temperature sensitivities and the history of shrinkage strain-rate.