Progress in the rheology of glass melts - A survey

Abstract

The rheology of glass melts is not restricted to Newtonian viscous flow, but it involves also non-Newtonian flow and viscoelasticity The former one predominates in the steady-state flow at low deformation rates, the latter ones prevail during the initial State of stress generation and during the final State of flow and fracture under extreme deformation conditions. The whole ränge of rheological phenomena is demonstrated in this review article. Typical available experimental results and mathematical formulations are briefly given for single-phase glass melts. In this context the development of new equations gives rise to the introduction of a series of new definitions and conceptions which physically and mathematically characterize the different rheological behaviour of glass melts under various stress-strain conditions. The connection between flow behaviour and structural aspects is pointed out with a short reference to flow birefringence. Finally, an extension from the behaviour of a single-phase to a double-phase system is developed for the case of suspended crystals with defined sizes, concentrations and shapes within an inert glass melt (model for glassceramic melts).