High-accuracy ultrasonic measurement of oil film thickness in sliding bearings considering surface thin coating

Focusing on the difficulty and inaccuracy of separating reflected waves from overlapping echoes caused by coating when measuring the oil film thickness of coated sliding bearings using ultrasonic. This paper proposes a pseudo reflection coefficient (PRC) constructed using the overall reflected wave and reference wave. And a robust PRC model is constructed to simultaneously calculate the oil film and coating thickness. Acoustic simulations verify the accuracy of the method and reveal that the PRC model has better stability. Application experiments are conducted on an actual aviation fuel gear pump. The good consistency between theory and experiment has demonstrated the effectiveness of the method. In addition, the elastic deformation of the bearing is derived based on the minimum oil film thickness.