Non-contact Measuring System for Surface Wear Dent of Journal Bearing

长期使用的滑动轴承表面经常会出现磨损凹痕，之所以会形成这些凹痕，是因为滑动轴承在启动或关闭过程中，流体动力油膜太薄，而轴承表面会直接接触金属。一旦形成磨损凹痕，油膜就会改变形状，最小油膜厚度可能会减小，从而危及轴承卡住。此外，转子动力学系数会发生变化，导致轴承支承的转子在达到额定转速之前发生自激振动。因此，必须精确测量轴承表面的磨损凹痕轮廓，以估计轴承性能的劣化。然而，目前在轴承安装现场还没有合适的测量系统。本研究旨在开发一种实用的新型测量系统，该系统可以方便、快速地检测大直径滑动轴承的表面磨损凹陷，分辨率达到微米级。采用电涡流型间隙传感器检测传感器与轴承表面的距离。传感器安装在旋转臂上，旋转臂又固定在梁上。光束可以在线性致动器中移动。因此，传感器可以在圆周方向和轴向扫描轴承表面。采集的距离数据在小型计算机中实时在线处理，并通过安装在计算机中的计算机程序自动计算磨痕轮廓。该程序是新开发和编码的。结果以图形和数字形式显示在监视器屏幕上。利用该系统对模型径向轴承表面人工加工的各种磨痕进行了测量，结果令人满意，测量精度较高。

Wear dents are often found on the surfaces of journal bearings in use for long, and these concave shapes are made because journals, make direct metal-to-metal contact with bearing surfaces while hydrodynamic oil films remain too thin during start-up or shut-down operation. Once the wear dent is formed, the oil film changes its shape, and the minimum oil film thickness may decrease, endangering bearing into seizure. Furthermore the rotordynamic coefficients would change, causing a self-excited vibration of rotor supported in the bearings before rated speeds are reached. Consequently, wear dent profiles on the bearing surfaces must be measured precisely to estimate the degradation of the bearing performance. However there exists no suitable measuring system available on the sites where bearings are installed.This research project aimed to develop a new handy measuring system for practical use that can easily and rapidly detect surface wear dents of journal bearings of large diameter with the resolution of some micrometer. A gap sensor of eddy-current type is used to detect the distance between the sensor and the bearing surface. The sensor is mounted on a rotating arm which, in turn, is fixed on a beam. The beam can move in a linear actuator. Thus the sensor can scan the bearing surface in the circumferential and also axial directions. The distance data collected are real-time processed on-line in a small-size computer, and wear dent profiles are calculated automatically by means of a computer program installed in the computer. The program was newly developed and coded. The results are presented graphically and numerically on a monitor screen. This system was used to measure various wear dents machined artificially on the surfaces of model journal bearings, and proved to function satisfactorily with precise measurements.