Wind turbine gearbox (WTG) bearings can fail prematurely, significantly affecting wind turbine operational availability and the cost of energy production. The current most commonly accepted theory of failure mechanism is that the bearing subsurface is weakened by white etching crack (WEC) networks that eventually lead to the flaking away of material from the bearing surface. Subsurface damage due to rolling contact fatigue (RCF) is thought to be the main cause of premature failure, resulting from the initiation of micro-cracks, often at non-metallic inclusions or other material defects, which then propagate to the bearing surface. This study proposes a hypothesis that impact loading together with high levels of surface traction and contact pressure are important factors contributing to the initiation of micro-cracks and white etching areas (WEAs) at non-metallic inclusions which may lead to the formation of WEC networks. Both repeated impact and twin-disc RCF tests were designed to investigate inclusion-initiated micro-cracks and WEAs at subsurface in order to test this hypothesis. This led to the recreation of inclusion-initiated micro-cracks and WEAs in tested specimens, similar to the subsurface damage observed at inclusions in failed WTG bearing raceways. Tests were carried out to determine threshold levels of contact pressure, surface traction, and impact loading required for the formation of inclusion-initiated micro-cracks and WEAs.

中文翻译：

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轴承钢中夹杂物引发的微裂纹和白蚀区域的阈值图：冲击载荷和表面滑动的作用。

风力涡轮机齿轮箱 (WTG) 轴承可能会过早失效，从而严重影响风力涡轮机的运行可用性和能源生产成本。目前最普遍接受的失效机制理论是，轴承表面下层因白蚀裂纹 (WEC ) 网络而被削弱，最终导致材料从轴承表面剥落。滚动接触疲劳 (RCF) 引起的表面下损伤被认为是过早失效的主要原因，这种损伤是由于微裂纹萌生而产生的，通常是在非金属夹杂物或其他材料缺陷处产生，然后扩展至轴承表面。这项研究提出了一个假设，即冲击载荷以及高水平的表面牵引力和接触压力是导致非金属夹杂物处出现微裂纹和白蚀区域(WEA) 的重要因素，这可能导致 WEC 网络的形成。重复冲击和双盘 RCF 测试旨在研究地下夹杂物引发的微裂纹和 WEA，以检验这一假设。这导致测试样本中重新出现由夹杂物引发的微裂纹和WEA，类似于在失效风力发电机组轴承滚道中的夹杂物处观察到的表面下损伤。进行测试以确定形成夹杂物引发的微裂纹和 WEA 所需的接触压力、表面牵引力和冲击载荷的阈值水平。