Gear fault and typical spectrum and waveform characteristics

Gear failure:



Gear wear: the better indication of gear wear is not the gear meshing frequency, but the natural frequency of the gear.



Large gear load: generally, when the load is high, the high meshing frequency and harmonic frequency of the gear will occur.



Gear meshing clearance: When there is clearance in gear meshing, the side band of the shaft will appear around the meshing frequency



Gear eccentricity: it will cause gear meshing frequency and natural frequency vibration, and it will also produce side band of fault gear



Gear misalignment: When the gear is misaligned, it will generally generate higher harmonics of gear meshing frequency, and the amplitude of the first harmonic is lower and the amplitude of the second harmonic is higher.



Broken teeth or large pieces of gear peeling off: high vibration will be generated at the speed frequency and natural frequency of the gear at this time, and there will be obvious impact in the time domain



Analysis of gear fault spectrum and waveform characteristics



1) The fault gear has a large vibration component in the meshing frequency and its harmonic frequency.



2) The sideband of the modulation effect near the meshing frequency and its harmonic component. The modulation frequency represented by the side frequency spacing can be



a) Speed of each shaft (input shaft, output shaft, intermediate shaft);



b) Fluctuation frequency of external speed or load;



c) Fluctuating meshing frequency. Namely (meshing frequency)/(minimum common multiple of driving gear and driven gear speed)



d) If there are more than two kinds of faults at the same time, the sum or difference of the fault frequency can also become the modulation frequency, called the intermediate frequency.



3) For helical gears, helical gears and herringbone gears, the axial vibration is large, and the spectrum characteristics are the same as the radial vibration.



4) Instrument setting: the maximum analysis frequency is about 4 times the gear meshing frequency. Spectrum (including refined spectrum and cepstrum), 800 lines.



Due to the complexity of spectrum analysis of gearbox, it is difficult to identify. An effective and feasible method is to collect the reference spectrum for each gearbox in good working condition, and find problems by comparing it with the reference spectrum in condition monitoring and fault diagnosis. For the measurement of bearing parts, if the vibration of each part is large, it may be a gear problem generally, and if the vibration of individual bearing parts is large, it may be a bearing problem