The Four Stages Of Rolling Bearing Failure

Rolling bearing is a kind of precision mechanical element which changes the sliding friction between the running shaft and the shaft seat into rolling friction so as to reduce the friction loss.The deterioration of rolling bearings is not a linear process, but an exponential process.In different deterioration stages, the fault information appears in different frequency band range, so different fault detection methods should be adopted.At present, it is generally believed in the industrial field that the deterioration of rolling bearings can be divided into four stages.
Stage 1: Initial bearing failure
Bearing at this stage in the first time the surface microscopic cracks or lattice mismatch, while bearing surface can't see the crack or small spalling, the vibration signal not obvious impact to low frequency signal, using traditional acceleration sensor can't pick up the fault signal, but The Times or micro crack on the surface of the lattice mismatch will produce acoustic emission signals or stress wave signal.Therefore, the fault characteristics of bearings at this stage are mainly reflected in the ultrasonic frequency band, which can be picked up by acoustic emission sensor or resonance-based acceleration sensor, and the main performance is that the measured signal peak value or energy value becomes larger.

Stage 2: Bearing failure development period
At this stage, the microscopic deterioration of bearings begins to expand from the secondary surface to the surface, and damage points such as cracks or tiny spalling occur on the contact surface of bearings.When surface and the damage point contact bearing components, can form a certain frequency of shock pulse, based on Fourier transform, the short-term impact of the signal in frequency domain is a broadband signal, so the impact signal will inevitably provoke bearing parts of high-frequency inherent frequency resonance occurs, so that the vibration strengthening, through the acceleration sensor can pick up to this part of the signal, using envelope demodulation technique could observe bearing fault characteristic frequency, at the end of phase 2 can also observe the frequency doubling fault characteristic frequency.At this stage, the fault characteristic frequency of bearings is temporarily submerged in the high noise in the low frequency band, so no clear fault characteristic frequency can be observed in the fault characteristic frequency band.
Stage 3: Rapid development of bearing failure
At this stage, with the accelerating development of bearing damage, damage to the impact of the bearing contact surface is more and more intense, in the bearing fault characteristic frequency of resonance frequency demodulation frequency doubling of more and more, and the size of cyclical impact energy was enough to directly observed through the power spectrum of vibration signals, this time can be directly in the clear on the power spectrum of bearing vibration signals of the fault characteristic frequency, and the trend of frequency doubling, more and more.
Stage 4: End of bearing failure
At this stage, the rolling bearing has nearly reached the end of its life, the damage point can be observed by the naked eye, the noise of the bearing movement becomes particularly large, and the temperature rises rapidly.Now direct power spectrum.Not only can we clearly see the bearing fault characteristic frequency and its multiple frequency, but also can see the obvious modulated edge frequency next to the fault characteristic frequency if the damage points alternately enter the load area.At the end of stage 4, the lines on the spectrum become less clear and protruding "thatch" forms in the power spectrum.In addition, the energy of high frequency vibration may also fall instead of rise at this time. If it is found that the monitoring amount of high frequency begins to decline, it is not that the condition of the surface bearing is getting better, but that the bearing is approaching the end of its life.

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