Viscosity annealing point

Figure 15.8 shows the temperature dependence of several glass compositions. Several temperatures are identified by viscosity the working temperature of a glass by 103 Pa s, the softening point by 4 x 106 Pa s, the anneal point by 2.5 x 1012 Pa s, and the strain point by 4 x 1013 Pa s. Glass objects are usually shaped... 

The viscosity parameters for a glass are softening point, 677 °C annealing point, 532 °C strain point, 493 °C. Estimate the activation energy for the viscosity. 

Figure 2-3 Temperature dependency of viscosity of commercial glass and various characteristic temperatures (Strain point lO poise. Annealing point poise. Softening...

Annealing point is the temperature at which the viscosity is 10 poise. Stresses that form in the glass object are relieved at this viscosity in a matter of minutes. 

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