Partial Load: A Key Factor Resulting in the Failure of Gear in the Wind Turbine Gearbox

Gearbox is a critical component in the wind turbine system which can transfer wind energy into wind power to replace some fossil energy in order to reduce the environmental pollution. A 1.5-MW wind turbine gearbox failed after about 5 years of service; however, the design life of the gearbox is 20 years. In this paper, the failure mechanism of the gearbox was investigated based on standard failure analysis procedures and finite element (FE) simulation. The failure of gear could be attributed to fatigue fracture, because typical macroscopic features—beach marks and ratcheting marks—could be observed on the fracture surface. Furthermore, contact fatigue caused the formation of pits on the failed working tooth flank, even brought some microcracks. It should be emphasized that fatigue pitting mainly concentrated at the left end of the failed gear. Based on the physical, chemical analysis, and FE simulation, the failure of gear should be essentially ascribed to abnormal load rather than the material defects. Finally, based on the failure characteristics, partial load should be responsible for the failure of the gear in the wind turbine gearbox.