Frequency and Vibration Characteristics of High-Speed Gear-Rotor-Bearing System with Tooth Root Crack considering Compound Dynamic Backlash

Abstract

Considering the microstructure of tooth surface and the dynamic characteristics of the vibration responses, a compound dynamic backlash model is employed for the gear transmission system. Based on the fractal theory and dynamic center distance, respectively, the dynamic backlash is presented, and the potential energy method is applied to compute the timevarying meshing stiffness, including the healthy gear system and the crack fault gear system. en, a 16-DOF coupled lateraltorsional gear-rotor-bearing transmission system with the crack fault is established. e fault characteristics in the timedomain waveform and frequency response and statistics data are described. e effect of crack on the time-varying meshing stiffness is analyzed. e vibration response of three backlash models is compared. e dynamic response of the system is explored with the increase in crack depth in detail. e results show that the fault features of countershaft are more obvious. Obvious fluctuations are presented in the time-domain waveform, and sidebands can be found in the frequency domain responses when the tooth root crack appears. e effect of compound dynamic backlash on the system is more obvious than fixed backlash and backlash with changing center distance. e vibration displacement along meshing direction and dynamic meshing force increases with the increase in crack depth. Backlash and variation of center distance show different tendencies with increasing crack depth under different rotational speeds. Amplitude of the sidebands increases with crack depth increasing. e amplitude of multiplication frequency of rotational frequency has an obvious variation with growing crack depth. e sidebands of the multiplication frequency of meshing frequency show more details on the system with complex backlash and crack fault.

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