The ultrasonic method has been widely applied to measure the oil film thickness – a critical variable that reflects lubrication conditions. However, due to the thermal dependence of ultrasonic signals, significant deviations in film thickness measurements are introduced, hindering the in-situ application of the ultrasonic technique. To address this issue, a real-time temperature compensation method that can accurately obtain the frequency domain information of the reference signal is proposed. Specifically, the reflection from the substrate-coating interface compensates for the thermal effect on the phase increment and amplitude attenuation – this is noted as “self-calibration”. An extra experimental test with a substrate-coating-air structure is performed to calibrate the thermal effect on the coating-induced phase shift – this part is denoted as “pre-calibration”. The combination of “self-calibration” and “pre-calibration” enables the overall temperature compensation strategy. After the effectiveness validation with a temperature-controlled experiment, the proposed method is implemented in a thrust bearing in a heavy-duty hydropower generator with full running conditions, including loading and unloading, normal speed and shut-down. The largely ranged oil film thickness (3–330 μm) is ultrasonically measured and compared with the theoretical value, showing a higher measurement accuracy than the eddy current method.

超声波方法已广泛应用于测量油膜厚度——反映润滑条件的关键变量。然而，由于超声波信号的热依赖性，在薄膜厚度测量中引入了显着偏差，阻碍了超声波技术的原位应用。针对这一问题，提出了一种能够准确获取参考信号频域信息的实时温度补偿方法。具体来说，来自基材-涂层界面的反射补偿了对相位增量和幅度衰减的热效应——这被称为“自校准”。使用基材 - 涂层 - 空气结构进行额外的实验测试以校准对涂层引起的相移的热效应 - 这部分表示为“预校准”。“自校准”和“预校准”相结合，实现了整体温度补偿策略。在通过温控实验验证了该方法的有效性后，该方法在某重型水轮发电机的推力轴承上实现了加卸载、常速、停机等全运行工况。超声测量大范围油膜厚度（3-330 μm）并与理论值进行比较，显示出比涡流法更高的测量精度。“自校准”和“预校准”相结合，实现了整体温度补偿策略。在通过温控实验验证了该方法的有效性后，该方法在某重型水轮发电机的推力轴承上实现了加卸载、常速、停机等全运行工况。超声测量大范围油膜厚度（3-330 μm）并与理论值进行比较，显示出比涡流法更高的测量精度。“自校准”和“预校准”相结合，实现了整体温度补偿策略。在通过温控实验验证了该方法的有效性后，该方法在某重型水轮发电机的推力轴承上实现了加卸载、常速、停机等全运行工况。超声测量大范围油膜厚度（3-330 μm）并与理论值进行比较，显示出比涡流法更高的测量精度。