Classification of Fault Diagnosis Techniques for Ball Bearings

The fault diagnosis technologies for ball bearings mainly include vibration diagnosis technology, ferrography diagnosis technology, temperature diagnosis technology, acoustic diagnosis technology, oil film resistance diagnosis technology, and fiber optic monitoring diagnosis technology. Among them, vibration, ferrography, and temperature diagnosis technology are widely used.

When fatigue peeling, indentation, or local corrosion occurs on the working surface of bearing components in vibration diagnosis technology, periodic pulse signals will appear during the operation of ball bearings. This periodic signal can be received by sensors (speed type or acceleration type) installed on the bearing seat, and bearing faults can be diagnosed through analysis of vibration signals.

Features: Vibration diagnosis technology is widely used; Can achieve online monitoring; Fast diagnosis, mature diagnostic theory, and application scope: particularly suitable for fault monitoring of bearings in rotating machinery

2. Ferrographic diagnosis technology is closely related to the wear particles of bearings and their working conditions. Lubricating oil with wear particles is subjected to a strong magnetic field, and under the action of the strong magnetic field, the wear particles precipitate on a ferrograph according to a certain pattern. The ferrograph can be qualitatively observed on a ferrograph microscope or tested on a quantitative instrument to determine the working condition of the bearing.

Features: The machine does not require disassembly; Low investment, good results; Early fatigue failure of bearings can be detected; Can conduct research on wear mechanism.

Application scope: Suitable for fault diagnosis of bearings lubricated with lubricating oil, which is more difficult for bearings lubricated with grease.

3. Oil film resistance diagnostic technology

A well lubricated bearing has a high resistance between the inner and outer rings due to the action of the oil film. Therefore, by measuring the resistance of the inner and outer rings of the bearing, the abnormality of the bearing can be judged.

Feature: The same evaluation criteria can be used for different operating conditions. The diagnostic effect on surface peeling, indentation, cracks and other abnormalities is poor. Application scope: Suitable for situations where the rotating shaft is exposed.

4. Fiber optic monitoring and diagnostic technology

Fiber optic monitoring is a diagnostic technique that directly extracts signals from the surface of bearing rings. The displacement sensor made of optical fiber bundles includes transmitting fiber bundles and receiving fiber bundles. The light is reflected back from the gap between the sensor end face and the bearing ring surface through the transmitting fiber bundle, received by the receiving fiber bundle, and converted into an electrical signal by the photoelectric element. By analyzing and processing the electrical signal, the bearing working condition can be evaluated.

Features: Fiber optic displacement sensors have high sensitivity; Directly extracting signals from the surface of bearings improves signal-to-noise ratio; It can directly reflect the manufacturing quality, surface wear degree, load, lubrication, and clearance of ball bearings.

Application scope: Suitable for machines that can install sensors in bearing seats.

5. Temperature diagnosis technology

If there is any abnormality in the bearing, the temperature of the bearing will change. Therefore, based on temperature changes, it is possible to diagnose ball bearing faults, but the ability to diagnose anomalies is very low.

Features: Simple diagnosis; The judgment effect on bearing burns is good.

Application scope: Suitable for simple routine diagnosis of bearings in machines.

6. Acoustic emission diagnostic technology

Metal materials require the release of elastic waves due to internal lattice dislocations, grain boundary slip, or the occurrence and development of internal cracks, which is called acoustic emission phenomenon. When ball bearings experience peeling or cracking, different types of acoustic emission signals are generated, which can be used to evaluate the bearing operating conditions.

Features: Fast and simple diagnosis; Can be monitored online Application scope: New technologies developed in recent years have been less applied in bearing condition monitoring.