Strain Transfer and Creep in All-Quartz Packaged SAW Strain Sensors

Design of the all-quartz package (AQP) for a resonant SAW strain sensing element is discussed and strain transfer to the surface of the SAW substrate is studied. Analytical results are compared with the FEA results. Based on the analytical model, creep and relaxation of strain on top of the SAW substrate is simulated using a viscoelastic model for the bond and the AQP frame adhesives. An experimentally observed anomalous creep of the resonant frequencies under a constant load is explained theoretically.