Abstract
AbstractPyrometric cone deformation is used to measure heat work or the combined effect of temperature and time during ceramic firing. Finite‐element analysis shows that stationary‐state temperature non‐uniformity in a pyrometric cone during constant‐rate heating can account for differences in observed endpoint temperatures at different heating rates. Thermophysical modeling provides evidence that two‐phase viscous flow plays an important role in pyrometric cone deformation. The Einstein‐Roscoe equation is used to calculate the effective viscosity of partially molten pyrometric cones during viscous flow deformation, with the solid phase volume fraction determined through thermophysical modeling and the molten phase viscosity estimated with the Modified Quasichemical Model. A correlation was found between the endpoint deformation temperatures of pyrometric cones and corresponding Littleton softening point temperatures; however, the approach fails when viscous flow is not the principal deformation mechanism and when the initial glass fraction exceeds the equilibrium molten phase fraction predicted by thermophysical modeling.
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