Few mysteries have stumped lubricant detectives as much as white etching cracks in highly loaded bearings. This mass killer, a type of rolling contact fatigue, starts below the metal surface and erupts into spidery, white-edged cracks, which then lead to pitting, spalling and early death for the component. WEC is spotted in equipment both large-wind turbines, power generation, paper mills-and small, such as variable transmissions in vehicles and high-speed machine spindles.
White etching cracking today especially is associated with a high level of unpredictable early bearing failures in wind turbines. At least, that is, basic theories of bearing life failed to predict them, commented Amir Kadiric, associate professor with the tribology group at Imperial College London. Design engineers had put the L10 prediction for wind turbine bearings-L10 being the point at which 10 percent of bearings will fail-at 20 years and beyond. To their mortification, that point was reached in a mere six months.