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Wind Turbines
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
Large bearings that do not rotate completely may show damage (known as false brinelling) in the raceways because of oscillation and vibration under high dynamic loads. In addition, many wind turbines are located close to bodies of water so humidity (along with rain) can cause bearing corrosion. Seawater in offshore applications can be even more of a problem and can cause heavy corrosion leading to high wear rates. Because of the heavy oscillating loads and possible water ingress, a special test was codeveloped by a German bearing builder (Rothe Erde) and a university (University of Aachen—IME) to simulate the conditions seen in pitch and yaw bearing applications. This test, referred to as the Riffel or Rippling test (Figure 16.14), uses heavy loads (70 kN/15,736 lb) oscillating at a frequency of 10 Hz for a total of 1 million load cycles. During the test, a 1% saltwater solution is pumped into the test bearing. After the test is completed, the bearing is examined for scar depth and corrosion (Figure 16.15).
Bearings and Seals
Published in Peter Lynwander, Gear Drive Systems, 2019
Two types of pitting failures that occasionally occur and are hard to diagnose are false brinelling and electrical pitting. False brinelling is a condition caused when the gear unit is subject to vibration while the shafts are not rotating, such as in transit during shipping. It is usually characterized by polished depressions spaced equal to the distance between rolling elements. False brinelling is a form of fretting corrosion.
Design Perspective of Wear Behavior
Published in Raymond G. Bayer, Engineering Design for Wear, 2019
False Brinelling: Damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be due to other causes such as fretting or fretting corrosion or local spots appearing when the protective film on a metal is broken continually by repeated impacts.
Effect of Lubricant Properties and Contact Conditions on False Brinelling Damage
Published in Tribology Transactions, 2023
Rachel Januszewski, Victor Brizmer, Amir Kadiric
False brinelling is a type of fretting wear that occurs in rolling bearings subjected to small-amplitude oscillations and manifests itself as distinct, evenly spaced craters on bearing raceways. A typical example of advanced false brinelling is shown in Fig. 1. It is caused by small-amplitude oscillations in the nonconformal contacts between the rolling elements and bearing raceways when bearings are nominally stationary. The oscillations within the contact are usually caused by some external source of vibration, for example, during transport of machines or in standby equipment located next to an operating machine. The craters replicate the shape of the ring-element contact and are spaced at the element pitch. The precise mechanisms of false brinelling are not entirely understood, but ultimately the damage is caused by significant metal-to-metal contact between the rolling element and the ring, which occurs due to the inability of the bearing lubricant to effectively penetrate the oscillating contact, and subsequent adhesive and other wear mechanisms taking place. In common with other types of fretting damage, false brinelling is associated with the formation of hard iron oxide debris that may remain trapped within the oscillating contact, thus facilitating further rapid wear through third-body wear mechanisms. False brinelling can lead to uneven running of the bearing, increased starting friction and bearing noise (1), and can ultimately cause a premature bearing failure (2).