Starvation and relubrication mechanisms in grease lubricated oscillating bearings

Sebastian Wandel*, Norbert Bader, Fabian Schwack, Jakob Glodowski, Bela Lehnhardt, Gerhard Poll

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

33 Citations (Scopus)

Abstract

Oscillating rolling element bearings can be found in various industrial applications. A popular example are the rotor blade bearings of wind turbines, which allow the rotor blades to turn around their longitudinal axis. These bearings are predominantly grease lubricated and expected to be running in a state of low velocity starvation. Elastohydrodynamic Lubrication (EHL) films in starved contacts are susceptible to the conditions of inlet lubricant supply. If the bearings are running under moderate starvation no early failure due to wear is expected. If the inlet conditions increasingly lead to a drying out of the contact, resulting in a heavily starved contact, metal-to-metal contact can lead to false brinelling and subsequent bearing failure. Using two different greases bearing experiments are used to gain an understanding of the mechanism of wear initiation. It is found that starvation seems to be a major contribution to wear appearing in the investigated operating conditions (2°-45° osc. angle, 0,2–5 Hz osc. frequency). The degree of starvation in the contact depends on the balance between lubricant displacement by the rolling element and the replenishment of lubricant during operation. The following conclusions could be drawn: Replenishment is highly dependent on the operating conditions such as the oscillation frequency, the oscillation amplitude, and lubricant rheology. For small oscillation angles the ability of the grease to release base oil with high mobility into the contact seams to be essential. For greater oscillation angles, after crossing a limiting angle, a secondary replenishment mechanism seems to become active. This prevents early wear initiation. At critical operating parameters, which mainly include high oscillation frequencies and medium oscillation angles, severe wear is initiated after just a few hundred oscillation cycles. By modifying an existing starvation factor the influences could be visualised and compared to the experimental results.

Original languageEnglish
Article number107276
JournalTribology international
Volume165
Early online date13 Sept 2021
DOIs
Publication statusPublished - Jan 2022
Externally publishedYes

Keywords

  • n/a OA procedure
  • Oscillating bearings
  • Relubrication
  • Starvation
  • Wear
  • False brinelling

Fingerprint

Dive into the research topics of 'Starvation and relubrication mechanisms in grease lubricated oscillating bearings'. Together they form a unique fingerprint.

Cite this