薄衬层结构滑动轴承润滑膜厚度的超声检测方法

A Method to Measure Thickness of Lubricant Film in Thin-Liner Sliding Bearings Using Ultrasonic Reflection

针对薄衬层结构滑动轴承润滑膜厚度超声检测时多次反射回波相互叠加而无法求取膜厚的问题,提出了超声回波信号叠加时润滑膜厚度的求解方法.根据叠加信号的频域分析方法,对薄衬层结构滑动轴承的润滑膜厚超声检测方法进行了理论分析.在原有需要取得轴瓦-空气界面参考反射回波信号的基础上,由厚村层轴瓦试件或理论计算得到基体-衬层界面的回波信号幅值谱.然后,分别取得参考回波、不同膜厚时的叠加回波信号与基体-衬层界面回波的频域幅值比,并按叠加信号间幅值比关系得到包含膜厚信息回波成分与基体-衬层界面回波成分在峰值频率处的幅值比,由此幅值比的变化关系得到膜厚测量过程中的反射系数值并最终确定润滑膜厚度值.实验结果表明：当润滑膜厚小于5μm时,测量结果与实际膜厚相吻合;随着膜厚增加,特别是大于7μm后,润滑膜的变化及其厚度由多次测量结果的均值表示.在2.3～10.3μm分布范围内的多次实验结果显示,该方法有较高的测量准确度.

An ultrasonic measurement method to measure lubricant film thickness in thin-liner bearing is proposed to solve the problem that the existing ultrasonic measurement methods could not be used to analyze the overlapped reflected pulses from sliding bearings with thin liner.The proposed ultrasonic measurement methods are theoretically analyzed based on the spectrum analysis method of overlapped signal.The signal from bearing substrate-liner interface is required,in addition to get the reference signal from bear liner-air interface.Then the frequencydomain amplitude ratios of overlapped signals and signal from substrate-liner interface are obtained.The amplitude ratio of film-thickness information composition from the overlapped signal and the constant composition from substrate-liner interface is obtained.The reflection coefficient is then obtained by comparing the amplitude ratio with the amplitude ratio of reference signal reflected from bearing bush-air interface,and the lubricant film thickness is then obtained from the reflection coefficient.Experimental results show that measurement results coincide well with the actual film thickness when the film thickness is less than 5 μm,and that the variation of lubricant film and its thickness are represented by the mean value of the multiple measurements when the film thickness increases.The multiple experimental results of film thickness in a range of 2.3-10.3 μm show that the method has a high measurement accuracy.