Stress relaxation of EAGLE XG® glass at 641 °C using three different strains corresponding to displacements of 0.075, 0.1, and 0.125 in. (a) Absolute stress as a function of time. (b) The normalized stress relaxation function collapses for all three strains. The solid line shows a fit with a stress relaxation time of τ = 1980 s and a stretching exponent of β = 3/5.
(a) Stress relaxation function of Jade® glass at 700, 735, and 758 °C. The symbols show the experimental data points, and the solid curves are fits using a stretching exponent of β = 3/5. (b) Stress relaxation time as a function of normalized inverse temperature, where T g = 782 °C.
(a) Relaxation of Jade® glass density during isothermal holds at 700, 735, and 758 °C and (b) the associated structural relaxation functions. The symbols show the experimental data points, and the solid curves represent fits using a stretching exponent of β = 3/7 for long-range forces.
(a) Stress and structural relaxation curves for Jade® glass, normalized by the particular relaxation times at each temperature (700, 735, and 758 °C). The stress and structural relaxation functions collapse onto master stretched exponential curves with β = 3/5 and β = 3/7, respectively. (b) Double-logarithmic plot of the relaxation function. Regression analysis yields R 2 values of 0.996 and 0.986 for the stress and structural relaxation data fit with β = 3/5 and β = 3/7, respectively. (c) Stress and structural relaxation times at each temperature. Structural relaxation is more than an order of magnitude slower than stress relaxation but has a lower activation barrier.
Optimized values of the stretching exponent β for stress and structural relaxation of Jade glass. The glass transition temperature of Jade glass is 782 °C. As discussed in the text, the β values for stress and structural relaxation are approaching the ideal values of 3/5 and 3/7, respectively, predicted by the diffusion-trap model in the low-temperature limit. Please note that more precise values of β can be obtained for the stress relaxation experiments given the much larger number of data points collected during these in situ measurements.
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