According to the structural composition of rolling bearings, there are four fault frequencies of rolling bearings: the fault frequency of rolling bearing cage, the fault frequency of rolling bearing body, the fault frequency of rolling bearing outer ring and the fault frequency of rolling bearing inner ring. For calculating the bearing fault frequency, have special mathematical formula, but in the practical work of calculation more troublesome, convenient method is to use special software, such as the United States with rockwell automation software in this feature plug-in, as long as the input bearing model and the information such as the manufacturer, they can get the corresponding all kinds of bearing failure frequency.

The first stage, namely, the embryonic stage of bearing failure, when the temperature is normal, the noise is normal, the total vibration speed and spectrum are normal, but the total peak energy and spectrum have signs, reflecting the initial stage of bearing failure. At this time, the real bearing failure frequency appears in the ultrasonic range of about 20-60khz.

In the second stage, the temperature is normal, the noise increases slightly, the total vibration speed increases slightly, the change of vibration spectrum is not obvious, but the peak energy increases greatly, and the spectrum is more prominent. At this time, the bearing failure frequency appears in the range of about 500HZ-2khz.

In the third stage, the temperature rises slightly, the noise can be heard, and the total vibration speed has a large increase, and the bearing fault frequency and its harmonics and side bands can be clearly seen in the vibration speed spectrum. In addition, the noise level on the vibration speed spectrum increases significantly, and the total peak energy becomes larger and more prominent than in the second stage. At this time, the bearing failure frequency appears in the range of about 0-1khz. It is recommended to replace the bearing at the late stage of the third stage, so the rolling bearing fault characteristics such as wear and tear should have appeared by this time.

In the fourth stage, the temperature increases significantly, the noise intensity changes significantly, the total vibration velocity and vibration displacement increase significantly, and the bearing fault frequency begins to disappear in the vibration velocity spectrum and is replaced by a larger random broadband high-frequency noise horizon. The total amount of peak energy increases rapidly, and some unstable changes may occur. Bearings must not be allowed to operate in the fourth stage of failure development, otherwise catastrophic damage may occur.

According to the results of the study, in general, if the whole service life of the rolling bearing is then counted from the time the bearing is installed and put into use, before it. 80% of the life time, the bearing is normal. Then, the residual life of rolling bearing is 10% ~ > in the first stage. 20%L10, 5%-10%L10 in the second stage, 1%-5% L10 in the third stage, and about 1h or 1%-L10 in the fourth stage.

Therefore, when facing bearing problems in practical work, considering that the fourth stage of the development of bearing faults has unexpected and sudden harm, it is suggested to replace bearings in the late third stage, so as to avoid the expansion of faults and the occurrence of more serious accidents, and to ensure the service life of rolling bearings as far as possible. Moreover, according to the rolling bearing fault characteristics such as wear and parts damage that can be seen by the naked eye, it is quite convincing. As for the identification of the late stage of the third stage of bearing fault development, it is necessary to comprehensively consider the above theoretical characteristics combined with the actual temperature, noise, speed spectrum, peak energy spectrum, total trend of speed and peak energy and practical experience.

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