Dynamic characteristics of spur gear system with tooth root crack considering gearbox flexibility

Considering the calculation efficiency and accuracy of meshing characteristics of gear pair with tooth root crack fault, the parametric model of cracked spur gear is established by simplifying the crack propagation path. LTCA method is used to calculate the time-varying meshing stiffness (TVMS) and transmission error (TE) of the cracked gear pair, and is verified by finite element (FE) method. The crack area share index is proposed to measure the degree of crack fault and the application range of simplified crack propagation path is obtained. The gearbox is introduced into the calculation as the condensation model, and the dynamic model of gear system with root crack fault considering gearbox flexibility is established. The effects of gearbox flexibility, rotational speed, crack degree and gear torque on the vibration response fault characteristics of gear system are analyzed. Compared with the simulation results without considering gearbox flexibility, the simulation results considering gearbox flexibility are smaller in amplitude and closer to the experimental results. The fault shock degree in acceleration waveform and fault frequency modulation in FFT spectrum are more obvious considering gearbox flexibility. The fault characteristics of vibration response are more obviously affected by the reduction of gearbox flexibility and the increase of fault degree than the change of rotational speed and gear torque. The research results provide theoretical and technical support for fault diagnosis and health monitoring of gear systems.