FEM Analysis of Time-Varying Meshing Stiffness of Wind Turbine Isolated Planetary Gear

The planetary stage of a wind turbine gearbox is very prone to gear failures due to the higher number of gears meshing in this stage. The study of the teeth mesh's internal excitations is crucial in investigating different failure occurrences in the gears. Hence, this study investigates the effects of the highly occurring gear failures (cracks and pits) on the meshing stiffness. A finite element method is utilized to determine the time-varying meshing stiffness (TVMS) of isolated sun-planet pair of a healthy planetary gear model. Two fault severities of cracks and pits with similar magnitudes are induced on a sun gear tooth of the planetary model, and their meshing stiffnesses are simulated. The simulation results of the healthy and faulty models with different faults and severities are compared. The TVMS of the less severe and more severe pit had a maximum deviation of 7.34% and 8.12%, respectively, from the healthy model, while crack had 8.57% and 16.88%, respectively. Also, the rate of damage progression of cracks was estimated to be ten times that of pits in the planetary gear. Therefore, tooth cracks are more dangerous to the smooth operation of wind turbines.