Bearing in the process of operation, due to the weary reason gradually degradation.
As shown in figure 1, degradation of rolling bearings is not a linear process, but a process index.
In different degradation stages, something wrong with the information presented in different frequency band range, so to adopt different fault detection method.
The current industrial category is generally thought that the degradation process of rolling bearings can is divided into four stages.
Figure 1 1 the first stage, the typical faults of bearing to carry out the process of bearing early failure, as shown in figure 2.
Bearing at this stage in the first time appearance of micro cracks or lattice mismatch, while bearing appearance can't see the crack or small spalling, the vibration signal will not constitute compare with obvious impact to low frequency signal, can't pick up to the problem with the traditional acceleration sensor, but the appearance of the micro cracks or lattice mismatch will produce acoustic emission signals or stress wave signal.
Therefore, at this stage bearing fault characteristic mainly displayed in the ultrasonic frequency, can through the acoustic emission sensor or acceleration sensor based on resonance stopped to pick up, the main performance for the measured signal peak or energy.
Figure 2 bearing degradation of the first phase of the vibration signal characteristics of the second phase, 2 bearing failure to carry out period, as shown in figure 3.
Bearing at this stage of the micro degradation beginning appearance by The Times to expand appearance, and cracks in the bearing contact appearance or small spalling damage point.
When appearance and the damage point contact bearing components, will constitute 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 resonance frequencies attack, making its vibration, through the acceleration sensor can pick up to the local signal, then the application of envelope demodulation technique can check to the bearing fault characteristic frequency, at the end of the second phase can also monitor the fault characteristic frequency in the frequency doubling.
At this stage, bearing fault characteristic frequency is consumed temporarily in high to low frequency noise, thus the fault characteristic frequency can't see clear the fault characteristic frequency.
Figure 3 bearing vibration signals of the second stage of the degradation characteristics of three phase three, bearing failure quickly develop period, as shown in figure 4.
At this stage, with the acceleration of bearing damage, damage to the impact of the bearing contact surface is more and more fierce, the resonance frequency demodulation of bearing fault characteristic frequency more and more frequency doubling and the cyclical impact of energy was enough to directly through the vibration signal power spectrum see come out, this time can directly in clear see on the power spectrum of bearing vibration signals of the fault characteristic frequency, and the frequency doubling has a tendency to be more and more.
Figure 4 bearing degradation is the third phase of the vibration signal characteristics of four stage 4, the end of bearing failure, as shown in figure 5.
At this stage, rolling bearing has quickly reached the end of life, can through naked eye view to damage point, bearing movement become particularly large noise, temperature rise sharply.
The direct power spectrum not only can clear see on bearing fault characteristic frequency and the frequency doubling, if damage points alternately into the load zone, also can see obvious beside the fault characteristic frequency modulation frequency.
In the fourth stage of the end of the spectrum lines become is not very clear, will constitute a bulge in power spectrum 'thatched heap', high frequency vibration energy at this time also may not rise but lower, if discover the high frequency measurement start landing, appearance is not the good bearing status, but rather to clarify bearing once is coming to the end of life.
Figure 5 bearing degradation in the fourth phase of the vibration signal characteristics of the place on put together is narrated, the four stages of degradation from bearing can see, bearing fault characteristic frequency in the frequency and the fault characteristic frequency can present the frequency doubling frequency have a certain level, can render response of the bearing degradation information, from the perspective of the relationship of frequency and time of bearing degradation has a tendency to be from high frequency to low frequency move, first the ultrasonic frequency measured signal changes, with the development of the bearing degradation, the resonance frequency of the signal after a certain analysis method can examine to the bearing fault characteristic frequency, finally within 1 KHZ low frequency signal power spectrum to look to the fault characteristic frequency.
Clarify this with the development of the bearing fault, the fault characteristics will gradually move from high frequency to low frequency.
