Mechanical simulation and test of force-sensitive element in surface acoustic wave contact stress sensor

In some harsh environments such as thin slits, the contact stress measurement with passive and wireless method faces huge challenges. In this paper a contact stress sensing system based on surface acoustic wave resonator (SAWR) is schemed, and the force-sensitivity element based on diaphragm structure is constructed. To meet the requirements in slits, the overall thickness of the device is limited under 400 μm. Moreover, the force-sensitive element with three parameters including shape, width and thickness of the cavity are built and simulated in FEA software (COMSOL Multiphysics). And the stress and strain results are discussed so as to determine proper parameters of sensor. Finally, the particular sensor based on circular diaphragm is manufactured and tested. The loading test results in 0-4MPa show that the sensor has a good linearity, and the sensitivity is 20.5 kHz/MPa. Therefore, this approach is proved to be feasible to monitor the contact stress in slits, which provides a novel method for physical quantity measurements in harsh environments as well.