Some aspects of the workability of glass melts

Abstract

Criteria are given for the isothermal or isochomal workability of glass melts and discussed by means of a schematic example which is based on numerous measurements. A thesis for a simple connection of this kind of workability is presented and examined by means of so far existing measurements. The isothermal or isochomal workability, which becomes more important with increasing deformation rate, is in contrast to the non-isothermal or athermal workability. The differences are based on certain connections between the stiffness, the relaxation modulus of a glass mek, its high-temperature fracture strength and the value of the quantity Β in the Vogel-Fulcher-Tammann (VFT) equation if the constants are evaluated from a measurement of the whole viscosity-temperature range, from 10^1.5 to 10^12 Pa s.