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Starvation and relubrication mechanisms in grease lubricated oscillating bearings
Leibniz Univ Hannover, Inst Machine Design & Tribol, DE-30167 Hannover, Germany..
Leibniz Univ Hannover, Inst Machine Design & Tribol, DE-30167 Hannover, Germany..ORCID iD: 0000-0003-0282-3417
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).ORCID iD: 0000-0003-2581-9672
Leibniz Univ Hannover, Inst Machine Design & Tribol, DE-30167 Hannover, Germany..
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2022 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 165, article id 107276Article in journal (Refereed) Published
Abstract [en]

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 degrees -45 degrees 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.

Place, publisher, year, edition, pages
Elsevier BV , 2022. Vol. 165, article id 107276
Keywords [en]
Oscillating bearings, Wear, False brinelling, Starvation, Relubrication
National Category
Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-303899DOI: 10.1016/j.triboint.2021.107276ISI: 000704334400001Scopus ID: 2-s2.0-85115160570OAI: oai:DiVA.org:kth-303899DiVA, id: diva2:1604980
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QC 20211021

Available from: 2021-10-21 Created: 2021-10-21 Last updated: 2025-02-14Bibliographically approved

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Schwack, Fabian

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