The correlation of the cooling rate with the fictive temperature and viscosity of glass

The cooling rate (q(c)) experienced by the basalt glass fibre during drawing is determined as function of the fictive temperature (T-f) in the range of 0.08 to 3x10(5) K/s using the finite element simulation (FEM) method and the differential scanning calorimetry (DSC) methods. The fragility of a glass melt can be described by the dependence of T-f on q(c). The quantitative correlation of the cooling rate with the viscosity and the Maxwell relaxation time is derived from the rheological and calorimetric measurements. The basis for a relaxation speedometry is verified for a broad range of cooling rates, which is of technological importance for controlling the rapid glass forming processes, e.g. the fibre drawing process.