Page 78 - 摩擦学学报2025年第9期

1332 摩擦学学报（中英文） 第 45 卷

Abstract: The oil film thickness is a key parameter for indicating the lubrication condition in tribological elements.
However, limited by the confined location space and the tiny scale of the oil film, it is a big challenge for the accurate oil
film thickness measurement. For the traditional ultrasonic oil film thickness measurement method, which utilizes the
amplitude of the reflected signal from the oil layer, there is normally a blind zone when using a single ultrasonic sensor
which severely limits the applications in industry. In this paper, a large-range ultrasonic oil film thickness measurement
method based on the phase of the reflected signal from the oil layer was developed, this method was able to eliminate the
measurement blind zone between the spring model measurement zone and the resonance measurement zone, and
achieved a wide range of oil film thickness measurement. The influence of the temperature on the measurement accuracy
of this method was analyzed and the compensation methods were proposed. The temperature could affect the
measurement accuracy of the oil film thickness phase measurement method by changing both the phase of the reference
signal and the acoustic parameters of the mediums. It was found that the phase of the reference signal change linearly as
the temperature and a linear curve which was fitted by the phase of the reference signals with different temperatures
could be constructed to compensate and eliminate the influence of the temperature on the phase of the reference signal.
For the influence of the change of the acoustic parameters induced by the temperature, the measurement errors caused by
the change of sound velocity in mediums were much bigger that than caused by the change of medium density. And
among the three mediums constructed the oil film, the measurement errors caused by the change of the oil density and
the sound velocity were the biggest, which reached 3.8% and 11.4% respectively. A calibration rig which consisted of
ultrasonic measurement module, oil film formation module, oil film calibration module, and temperature control module
was built to verify the accuracy of the proposed method under constant temperature and varying temperatures. The
measured results was compared with both the set values and that obtained by the capacitance sensor. The test results
indicated that the measurement error of the developed method was less than 8% under constant temperature, the
temperature change would deteriorate the measurement precision and the measurement precision could be improved
effectively with the temperature compensation method developed in this paper, decreasing the maximum measurement
error down to 20% under varying temperatures. Furthermore, the proposed measurement method exhibited a good
robustness under various temperatures. This paper could provide an effective ultrasonic measurement method for large
range oil film thickness with single ultrasonic sensor. It also could enrich the ultrasonic oil film thickness measurement
method and provide a reference for engineering applications.
Key words: oil film thickness; ultrasonic measurement; phase; large-range; temperature

润滑油膜厚度是表征轴承和密封等摩擦学元件 是1种优良的非介入式检测方法，颇具工业应用前景，
润滑状态的关键性能指标，其大小直接决定了摩擦学 近年来获得了学术界与工业界的广泛关注.
元件的润滑性能、承载能力、运行平稳性和寿命等行 润滑油膜厚度超声检测方法根据其测量原理的
[10]
为能力，是摩擦学元件的关键所在. 然而，由于润滑油 不同通常分为飞行时间法 、共振法 [11-12] 和弹簧模型
膜所处空间的密闭性和尺寸的微小性等特点制约了 法 [13-16] . 飞行时间法通过测量超声波在润滑油膜上下
实际工业中摩擦学元件润滑油膜厚度检测的实施与 界面反射信号的时间差和超声波在润滑油中的声速
发展，一直以来，学者们基于润滑油膜层的光学、电学 计算润滑油膜厚度，该方法需要超声波在润滑油膜层
和声学特性提出多种润滑油膜厚度检测方法. 根据测 上下界面的反射信号相互分离，因此通常只适用于精
量原理的不同，润滑油膜厚度光测法分为光干涉法 [1-3] 、 确测量100 μm以上的润滑油膜厚度. 共振法利用超
[4]
光衍射法和光纤位移传感器法 ，光测法测量精度高， 声波在润滑油膜层反射信号幅值谱中极小值对应的
其测量油膜厚度可以达到纳米级精度 ，但光测法要 频率值计算润滑油膜厚度，超声波中心频率越高，共
[5]
求摩擦学元件至少一侧采用透光材料或设置透明窗 振法可以测量的油膜厚度越薄，然而超高频率超声波
口为其提供光路，因此多用于实验室的测试研究；润 在金属介质中衰减严重而无法传播，通常在金属介质
滑油膜厚度电测法分为电阻法 [6-7] 和电容法 [8-9] 等，润滑 中能够有效传播的最大的超声波中心频率为60 MHz
[14]
油膜厚度电测法需要在摩擦副的2个元件表面间建立 左右，共振法可以测量的最小油膜厚度约为10 μm .
电回路，难以实际应用. 得益于超声波具有良好的穿 弹簧模型法适用于膜厚远小于超声波在润滑油中
[17]
透性和直线传播的特性，润滑油膜厚度超声检测方法 波长的情况 ，其通过超声波在润滑油膜层上的反射