Study on temperature dependence of modal frequencies for microstructures based on air-coupled ultrasonic excitation
To study the temperature characteristics of flexural vibration modal frequencies for microcantilevers,the theoretical models of temperature-frequency coefficients were established for anisotropic materials microcantilevers with constant rectangular cross-section.Then,a non-contact dynamic characteristic testing system for microstructures was constructed,including a laser vibrometer unit,air-coupled ultrasonic excitation unit,and temperature control unit.Finally,using the established testing system,the dynamic characteristics of single-crystal silicon microcantilevers with constant rectangular cross-section were tested over a temperature range from room temperature to 300℃.The change regularities with temperatures of the first three-order flexural vibration modal frequencies for the silicon microcantilever were figured out,and the temperature coefficients of the first three-order modal frequencies were obtained.The results indicate that the first three bending vibration modal frequencies of the single-crystal silicon microcantilevers approximately linearly decrease with increasing temperature.Moreover,the temperature coefficients of the first three-order modal frequencies are almost the same.Specifically,the temperature coefficient for the first modal frequency is-2.18×10-5/℃,for the second modal frequency is-1.91×10-5/℃,and for the third modal frequency is-2.01×10-5/℃.The deviations of the test results of the temperature coefficients of the first three modal frequencies from the predicted values of the theoretical model are 3×10-7/℃,3×10-6/℃and 2×10-6/℃,respectively.
air-coupled ultrasonic excitationmicrostructurestemperature coefficient of frequenciesflexural vibration modal
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