A rolling bearing is a precision mechanical component that changes the sliding friction between the running shaft and the shaft seat into rolling friction, thereby reducing friction loss. Rolling bearings are widely used in electromechanical equipment, and their state is directly related to the operating state of the rotating equipment. Therefore, in the actual production process, the state detection and fault diagnosis of rolling bearings are an important part of equipment maintenance and management.
Rolling bearings generally consist of an inner ring, an outer ring, a rolling element and a cage. Corresponding to the rolling bearing structure, the typical fault characteristics of the rolling bearing correspond to four fault frequencies: bearing outer ring defect frequency (BPFO), bearing inner ring defect frequency (BPFI), bearing rolling element defect frequency (BSF), bearing cage defect frequency (FIF), and Higher harmonics of the four characteristic frequencies. And if the inner ring (or outer ring) of the rolling bearing rotates relative to the shaft, in this case, the inner (outer) ring fault frequency of the bearing is modulated by the small rotational frequency of the inner (outer) ring of the bearing. A sideband near the frequency of failure can be seen in the spectrum.
When a small failure occurs in the rolling bearing, the late damage development of the bearing changes exponentially. Bearing failure development can generally be divided into four stages.
The first stage: the bearing begins to malfunction, then the temperature is normal, the noise is normal, the vibration spectrum changes little, there is no bearing failure frequency, but the vibration peak energy increases. At this time, the remaining bearing life is greater than.
The second stage: the temperature is normal, the noise is slightly increased, the total vibration speed is increased, and the vibration peak energy is greatly increased, but the frequency of the fault characteristic is hardly seen on the vibration spectrum diagram. At this time, the remaining bearing life is about.
The third stage: the noise can be heard and the temperature rises slightly. The total vibration velocity has a large increase, the peak energy is larger than the second phase, and the apparent bearing fault frequency, harmonics and their side frequencies can be seen in the vibration velocity spectrum. At this time, the bearing life is less than this, it is recommended to replace the bearing.
The fourth stage: the temperature is obviously increased, the noise intensity is obviously changed, the total vibration speed and the total vibration displacement are obviously increased, and the fault frequency in the vibration speed spectrum begins to disappear, and is replaced by a larger random broadband high-frequency noise. At this time, the remaining life of the bearing is less than that, and catastrophic damage may occur at any time.
In actual work, we can judge the fault according to the fault feature type, and can estimate the bearing life according to the fault degree. This can avoid the occurrence and expansion of faults, and can guarantee the service life of the bearings as much as possible.
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