机械结构流体层厚度超声测量方法理论研究

针对机械设备运行状态监控需要,对机械结构流体层厚度超声测量方法进行了理论研究。根据流体层厚度超声测量的实际情况,建立了超声波在三层介质中传播的理论模型,并由边界连续条件,得到流体层超声波反射系数的连续模型。通过对不同厚度流体层反射系数曲线的理论分析,得到流体层厚度超声反射系数测量的谐振模型和弹簧模型,即通过流体层的谐振频率和刚度系数来表征其厚度。同时,研究了三层介质的声学特性对流体层超声反射系数及厚度测量的影响。

Theoretical research on thickness measurement of fluid layer in mechanical structure by using ultrasonic technique

For the necessity of monitoring mechanical structure operation, the thickness measurement of thin fluid layer in mechanical structure by using ultrasonic technique is theoretically studied. A model of three layers of media is constructed to simulate the propagation of normal incidence ultrasound. Considered the continuous boundary conditions, the reflection coefficient of thin fluid layer to normal incidence longitudinal waves is obtained from the continuous model. By study the reflection coefficients of different thicknesses of fluid layers, two models, resonant model and spring model, are developed to characterize the thickness of fluid layer respectively by the resonant frequency and stiffness coefficient. Meanwhile, the influence of acoustic properties of three layers on the reflection coefficient and the measurement of thickness is studied.