油膜厚度超声测量声反射系数理论及数值计算

Theory and Numerical Calculation of Acoustic Reflection Coefficient for Oil Film Thickness Measurement

实际润滑系统中油膜厚度较小,常规的超声测量方法不再适用。根据声学理论,分析多层介质中油膜厚度与声反射系数的关系,建立2种不同的油膜厚度测量理论模型,即共振模型和弹簧模型,讨论不同模型的适用范围。针对不同的理论模型,建立其相应的有限元模型,在后处理中通过驻波理论对界面反射系数进行计算,并与理论曲线进行对比,两者具有很好的一致性,证明有限元法计算油膜反射系数的准确性。研究结果表明:对于不同的超声频率,每种模型都有对应的油膜厚度测量区间,在实际测量中,要根据声波频率来确定每种模型的测量区间。

Due to the small thickness of oil film in the actual lubrication system,conventional ultrasonic measurement methods are no longer applicable.Based on acoustic theory,the relationship between oil film thickness and acoustic reflection coefficient in multi-layer media was analyzed.Two different theoretical models of oil film thickness measurement,the resonance model and the spring model were established,and the applicable range of different models was discussed.The corresponding finite element model was established for different theoretical models.The reflection coefficient of the interface was calculated by the standing wave theory and compared with the theoretical curve.It is proved that the finite element method can be used to calculate oil film reflection coefficient accurately.The results show that each model has corresponding oil film thickness measurement interval for different ultrasonic frequencies.In actual measurement,the measurement interval of each model should be determined according to the ultrasonic frequencies.