# Fault vibration characteristics of gear transmission system

Taking the typical fault vibration characteristics of gear transmission system as the research object, the time-varying meshing stiffness of gear pair is obtained by energy method, and the dynamic model of gear pair constructed by lumped mass method and Lagrange equation is combined. The root crack is introduced into the dynamic model through bending stiffness and shear stiffness to form the vibration analysis method of gear pair with root crack Lange equation is used to establish the dynamics of rolling bearing, and the dynamic model is introduced by contact deformation to form the vibration analysis method of rolling bearing local fault; the vibration characteristic analysis method of gear transmission system is developed by integrating the dynamic model of gear pair and rolling bearing, and the typical faults such as root crack and bearing local fault are deeply studied The influence law of vibration characteristics. The following conclusions were obtained

1) The results show that the time-varying meshing stiffness of gear pair is single tooth meshing area and double tooth meshing area, and the meshing stiffness of single tooth meshing area is obviously smaller than that of double tooth meshing area, and the meshing stiffness changes abruptly at the junction of single tooth meshing area and double tooth meshing area; root crack reduces the time-varying meshing stiffness of gear pair, and the influence of crack depth and development angle on the meshing stiffness of gear pair As the meshing point of the gear tooth gradually moves from the root to the top of the tooth, the periodic impact wave appears on the vibration time domain diagram of the gear pair with root crack, which is more obvious with the increase of the crack depth. There is a side band between the meshing frequency and its multiple frequency in the frequency domain diagram, and the amplitude of the side band increases with the increase of the crack depth.

2) When rolling element and raceway fault area act, impact load will be produced, which will cause periodic impact signal in vibration time domain diagram of bearing outer ring; when rolling bearing has single fault, fault characteristic frequency can be clearly shown in frequency domain diagram, and fault location can be judged by time interval of adjacent impact signal in time domain diagram, and different faults have different faults The characteristic frequency corresponds to different time periods; when the rolling element and the inner raceway fail at the same time, the fault characteristic frequency of the inner raceway in the frequency domain diagram is stronger than that of the rolling element fault; when the rolling element and the outer raceway are in fault at the same time, the amplitude of the fault characteristic frequency of the rolling element in the frequency domain diagram is greater than that of the outer raceway; when the inner and outer raceways fail at the same time, the inner rolling in the frequency domain diagram is larger than that in the frequency domain diagram The amplitude of the fault characteristic frequency of the inner raceway is larger than that of the outer raceway; when the rolling element and the inner and outer raceways are in fault at the same time, the amplitude of the fault characteristic frequency of the inner raceway is the largest, that of the rolling element is the second, and that of the outer raceway is the smallest.

3) When the root crack is combined with the bearing outer raceway fault, the gear fault characteristic frequency in the gear transmission system spectrum diagram and the rolling bearing outer raceway fault characteristic frequency are obvious; when the tooth root crack and the bearing inner raceway fault compound, the gear fault characteristic frequency and bearing inner raceway characteristic frequency amplitude in the gear transmission system spectrum diagram are obvious When the root crack and the bearing roller fault compound, the gear fault characteristic frequency is obvious, but the rolling bearing inner raceway fault characteristic frequency amplitude is very small, it is difficult to be found; when the tooth root crack and bearing inner and outer raceway fault compound, the fault characteristic frequency is obvious, and the gear fault characteristic frequency amplitude is the largest; the root crack, bearing roller fault and outer raceway fault compound When the gear root crack, bearing rolling element fault and inner raceway fault are combined, the inner raceway fault characteristic frequency and gear fault characteristic frequency are more obvious, and the side band with the interval of rotor frequency appears around the inner raceway fault characteristic frequency, and the rolling element fault characteristic frequency is weak When the root crack, bearing inner raceway fault, outer raceway fault and rolling element fault occur simultaneously, the gear fault characteristic frequency amplitude is the largest, the inner raceway fault characteristic frequency is the second, followed by the outer raceway fault characteristic frequency, and the rolling element fault characteristic frequency is the weakest.

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