Influence of Viscoelastic Stress Relaxation of Glass-Frit Sealing Layer on the Frequency Stability of a Dual-Mode Quartz Pressure Sensor Under Extreme Pressure Conditions

An exhaustive and rigorous stress analysis has been carried out to investigate the influence of viscoelastic stress relaxation of the glass-frit layer on the frequency shift of the dual-mode quartz (AXQG) pressure gauge. Static stress analysis results obtained from three different FEA software shows good agreements for different pressure-temperature (P/T) conditions. The estimated pressure sensitivity of the C-mode from the stress analysis shows a good agreement with the measured C-mode pressure sensitivity. Dynamic analysis results, where the viscoelastic property of the glass-frit is taken into consideration, show good agreement between different FEA software and measured data when the AXQG sensor is subjected to a constant P/T condition for several days. Results show that with an increase in temperature, the stress relaxation due to the viscoelastic deformation of the glass-frit becomes significant that affects the frequency stability of the thickness-shear modes of the AXQG sensor. The magnitude of the frequency drift increases substantially under the influence of high pressures and temperatures. However, at low temperatures and high pressures the frequency drift is negligible.