Viscous Flow in Glass‐to‐Metal Seals

Abstract

Birefringence measurements were made on glass‐to‐metal seals with simple geometries during cooling at various rates. Thermal contraction data were also obtained on the metal and on the glass while cooling at the same rates. Using these data, the viscosity of the glass during cooling at a constant rate was calculated. The viscosity deviates markedly from the equilibrium curve and is a function of cooling rate in this temperature region. Viscous flow in the seal is measurable as much as 125°C. below the strain point.