Effects of Tooth Directional Modification Error on Internal Excitation and Vibration Characteristics of Gears with Early-Stage Crack Fault

Tooth directional modification (TDM) is a widely used method to eliminate the stress concentration at the edge of gear teeth, and plays a key role in vibration and noise reduction and life extension of gears. The existence of TDM and early-stage crack (ESC) will both change the tooth contact characteristic and then cause the variation of internal excitation and vibration characteristics of the gear system. However, the coupling effect of the ESC and TDM on the tooth contact characteristic is usually ignored in the existing internal excitation modelling and vibration characteristic simulation of the gear system with ESC, causing the effect of TDM on the ESC excitation characteristics is still unclear. To address this shortcoming, an internal excitation analytical model of the gear system with ESC is established considering this coupling. On the basis of verifying the correctness and accuracy of the proposed model, the influence mechanism of TDM on the internal excitation and vibration characteristics of the gear with ESC is investigated. The results show that the effects of the gear contact characteristic changes caused by the TDM on the gear internal excitation are much greater than that resulting from the ESC, and the vibration characteristics of the ESC can be easily distracted by the TDM errors. Therefore, it is suggested that the TDM errors should be taken into account in the early-stage fault simulation or diagnosis method establishment to avoid the simulation results deviating from the actual situation.