Tooth flank fracture in a wind turbine gearbox—A failure analysis
摘要
During the last two decades, electricity generation by wind power increased rapidly. This is mainly due to efforts to reach CO2 neutrality and the low levelized cost of wind energy. Also, the power generated by a single wind turbine with a gearbox steadily grew during the last years, reaching up to 15 MW in prototypes by 2023. High power density due to limited installation space and those high output powers result in multiple challenges for the gearboxes and their design. As the tooth root and the tooth flank (pitting) load-carrying capacity steadily increased due to, e.g., special treatments of the gears, in recent years, the damage type of tooth flank fracture (TFF) has become one of the main concerns when designing a new wind turbine gearbox. This paper analyzes a TFF failure observed in the highspeed stage of a 2.1 MW onshore wind turbine gearbox. The analysis comprises documentation of the failure and a metallographic investigation of the failed gear. In a second step, the TFF risk of this stage is calculated according to ISO/TS 6336‑4. The results of this calculation are contrasted with those of a higher-order TFF calculation model, which also considers tensile residual stresses in the core of the material. These calculations explain why the gearbox failed due to TFF.