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

When the working surface of bearing components experiences fatigue peeling, indentation, or local corrosion 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 the fault of the bearing can be diagnosed by analyzing the vibration signal.

Characteristics: Vibration diagnosis technology is widely used; Can achieve online monitoring; Fast diagnosis and mature diagnostic theory. Application scope: Especially suitable for fault monitoring of bearings in rotating machinery. 2. Iron spectrum diagnosis technology has a close relationship between bearing wear particles and their working conditions. Lubricating oil with wear particles is passed through a strong magnetic field, and under the action of the strong magnetic field, the wear particles precipitate on the iron spectrum plate according to a certain pattern. The iron spectrum plate can be qualitatively observed on an iron spectrum 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; Can detect early fatigue failure of bearings; Can be used to study the 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 large 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, abnormalities in the bearing can be determined.

Characteristic: The same evaluation criteria can be used for different working 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 a transmitting fiber bundle and a receiving fiber bundle. The light is reflected back from the emitting fiber bundle through the gap between the sensor end face and the bearing ring surface, 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: High sensitivity of fiber optic displacement sensor; Directly extracting signals from the bearing surface improves the 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 inside 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, ball bearing faults can be diagnosed, but the ability to judge abnormalities 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, a phenomenon known as acoustic emission. When ball bearings peel off or crack, different types of acoustic emission signals are generated, which can be used to evaluate the working conditions of the bearings.

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