Editing False brinelling

{{use dmy dates |date=September 2020}}
[[File:FB-geschaedigtes Lager.jpg|thumb|False brinelling of a bearing]]
'''False brinelling''' is a [[Bearing (mechanical)|bearing]] damage caused by [[fretting]], with or without [[corrosion]],<ref>{{Cite web|url=https://www.researchgate.net/publication/316543220|title=Time-dependent analyses of wear in oscillating bearing applications (PDF Download Available)|last=Schwack|first=Fabian|date=2017-05-25|website=ResearchGate|access-date=2017-06-27}}</ref> that causes imprints that look similar to [[brinelling]], but are caused by a different mechanism. False brinelling may occur in bearings which act under small oscillations<ref>{{Cite web|url=https://www.researchgate.net/publication/309585771|title=Service Life of Blade Bearings - Problems Faced in Service Life Estimation of Blade Bearings|last1=Schwack|first1=Fabian|last2=Poll|first2=Gerhard|website=ResearchGate|access-date=2017-06-27}}</ref> or vibrations.<ref>{{Cite journal|last=Pittroff|first=Hans|date=1965-09-01|title=Fretting Corrosion Caused by Vibration With Rolling Bearings Stationary|journal=Journal of Basic Engineering|volume=87|issue=3|pages=713–723|doi=10.1115/1.3650657|issn=0098-2202}}</ref>

The basic cause of false brinelling is that the design of the bearing does not have a method for redistribution of [[lubricant]] without large rotational movement of all bearing surfaces in the raceway.<ref>{{Cite journal|last1=Schwack|first1=Fabian|last2=Bader|first2=Norbert|last3=Leckner|first3=Johan|last4=Demaille|first4=Claire|last5=Poll|first5=Gerhard|date=2020-08-15|title=A study of grease lubricants under wind turbine pitch bearing conditions|journal=Wear|language=en|volume=454-455|pages=203335|doi=10.1016/j.wear.2020.203335|issn=0043-1648|doi-access=free|url=https://repo.uni-hannover.de/bitstreams/0d6b4871-9466-4ad3-9ca6-de19dc849708/download}}</ref> Lubricant is pushed out of a loaded region during small oscillatory movements and vibration where the bearings surfaces repeatedly do not move very far.<ref>{{Cite book|title=Advanced Tribology|last1=Feng|first1=Chen|last2=Maruyama|first2=Taisuke|last3=Saito|first3=Tsuyoshi|date=2009|publisher=Springer, Berlin, Heidelberg|pages=42–43|doi=10.1007/978-3-642-03653-8_16|chapter = Oil Film Behavior under Minute Vibrating Conditions in EHL Point Contacts|isbn = 978-3-642-03652-1}}</ref> Without lubricant, wear is increased when the small oscillatory movements occur again.  It is possible for the resulting [[wear]] debris to [[Oxide|oxidize]] and form an abrasive compound which further accelerates wear.

==Mechanism of action==

In normal operation, a rolling-element [[Bearing (mechanical)|bearing]] has the rollers and races separated by a thin layer of lubricant such as [[grease (lubricant)|grease]] or [[oil]].<ref>{{Cite journal|last1=Maruyama|first1=Taisuke|last2=Saitoh|first2=Tsuyoshi|last3=Yokouchi|first3=Atsushi|date=2017-05-04|title=Differences in Mechanisms for Fretting Wear Reduction between Oil and Grease Lubrication|journal=Tribology Transactions|volume=60|issue=3|pages=497–505|doi=10.1080/10402004.2016.1180469|s2cid=138588351|issn=1040-2004}}</ref><ref>{{Cite web |title=Mastering Bearing Lubrication Systems: Ensuring Smooth Operations |url=https://fhdbearings.com/blog/bearing-lubrication-systems/#elementor-toc__heading-anchor-20 |access-date=2024-11-12}}</ref><ref>{{Cite web |title=Was sind Radlager und was ist ihre Funktion? |url=https://www.autodoc.de/info/wie-viel-kostet-es-die-kaputten-radlager-eines-autos-zu-wechseln |access-date=2024-11-12}}</ref>  Although these lubricants normally appear liquid (not solid), under high pressure they act as solids and keep the bearing and [[race (bearing)|race]] from touching.<ref>{{Cite web|url=https://de.scribd.com/document/122449861/Fretting-Corrosion-or-False-Brinelling|title=Fretting Corrosion or False Brinelling {{!}} Wear {{!}} Surface Science|last=Godfrey|first=Douglas|website=Scribd|access-date=2017-06-27}}</ref><ref>{{Cite journal|url=https://www.researchgate.net/publication/286233368|title=Another perspective: False brinelling and fretting corrosion (PDF Download Available)|pages=34–36|last=Errichello|first=Robert|date=April 2004|journal=Lubrication Engineering|volume=60|access-date=2017-06-27}}</ref>

If the lubricant is removed, the bearings and races can touch directly.  While bearings and races appear smooth to the eye, they are microscopically rough.  Thus, high points of each surface can touch, but "valleys" do not.  The bearing load is thus spread over much less area increasing the contact [[Stress (mechanics)|stress]],<ref>{{Cite journal|last1=Tonazzi|first1=D.|last2=Komba|first2=E. Houara|last3=Massi|first3=F.|last4=Le Jeune|first4=G.|last5=Coudert|first5=J. B.|last6=Maheo|first6=Y.|last7=Berthier|first7=Y.|date=2017-04-15|title=Numerical analysis of contact stress and strain distributions for greased and ungreased high loaded oscillating bearings|journal=Wear|series=21st International Conference on Wear of Materials|volume=376–377, Part B|pages=1164–1175|doi=10.1016/j.wear.2016.11.037}}</ref> causing pieces of each surface to break off or to become pressure-welded then break off when the bearing rolls on.

The broken-off pieces are also called ''wear debris''.  Wear debris is bad because it is relatively large compared to the surrounding surface finish and thus creates more regions of high contact stress.  Worse, the steel in ordinary bearings can oxidize ([[rust]]),<ref>{{Cite journal|last=Tomlinson|first=G. A.|date=1927-07-01|title=The Rusting of Steel Surfaces in Contact|journal=Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences|volume=115|issue=771|pages=472–483|doi=10.1098/rspa.1927.0104|issn=1364-5021|bibcode=1927RSPSA.115..472T|doi-access=free}}</ref> producing a more abrasive compound which accelerates wear.

== Simulation of false brinelling ==
The simulation of false brinelling is possible with the help of the finite element method. For the simulation, the relative displacements (slip) between rolling element and raceway as well as the pressure in the rolling contact are determined. For comparison between simulation and experiments, the friction work density is used, which is the product of friction coefficient, slip and local pressure. The simulation results can be used to determine critical application parameters or to explain the damage mechanisms.<ref>{{Cite journal|last1=Schwack|first1=F.|last2=Prigge|first2=F.|last3=Poll|first3=G.|date=October 2018|title=Finite element simulation and experimental analysis of false brinelling and fretting corrosion|journal=Tribology International|volume=126|pages=352–362|doi=10.1016/j.triboint.2018.05.013|s2cid=139773784 |issn=0301-679X}}</ref>
[[File:Simulation der Reibarbeitsdichte.png|center|thumb|Comparison between simulated frictional work density and wear]]Physical simulation of the false brinelling mechanism has been standardized since the 1980's in the Fafnir Bearing test instrument, where two sets of thrust ball bearings are compressed with a fixed load, and the bearings are oscillated by an excentric arm under standardised conditions.  This culminated in the ASTM D4170 standard.<ref>{{Cite journal |last1=Grebe |first1=Markus |last2=Widmann |first2=Alexander |date=July 2023 |title=Comparison of Different Standard Test Methods for Evaluating Greases for Rolling Bearings under Vibration Load or at Small Oscillation Angles |journal=Lubricants |language=en |volume=11 |issue=7 |pages=311 |doi=10.3390/lubricants11070311 |doi-access=free |issn=2075-4442}}</ref><ref>ASTM D4170, Standard Test Method for Fretting Wear Protection by Lubricating Greases</ref>  Although an old method, this is still the leading quality control method for greases that need to avoid the false brinelling damage.

[[File:Test bearings Fafnir False Brinelling test.jpg|alt=Test bearings for ASTM D4170 False Brinelling fretting wear test|left|thumb|330x330px|Test bearings for ASTM D4170 False Brinelling fretting wear test]]


[[File:FafnirFrettingWearTester.jpg|alt=False Brinelling Fretting wear tester|center|thumb|452x452px|False Brinelling Fretting wear tester]]







==Examples==
False brinelling was first mentioned by Almen in 1937.<ref>{{cite journal|last1=Almen|first1=J.O.|title=Lubricants and False Brinelling of Ball and Roller Bearings|journal=Mechanical Engineering|date=1937|volume=59|issue=6|pages=415–422}}</ref> Almen found that wheel bearings were damaged before they were used by customers. Furthermore, he found that the bearings were more damaged for long-distance shipping of the cars and that the season of shipping also had an influence. The reason for the damaged bearings were micro-oscillations<ref>{{cite journal|last1=Pittroff|first1=Hans|title=Fretting Corrosion Caused by Vibration With Rolling Bearings Stationary|journal=Journal of Basic Engineering|date=1965|volume=87|issue=3|pages=713–723|doi=10.1115/1.3650657}}</ref> which occurred due to the shipping.  The small oscillations result in fatigue cracking, followed by release of particles that subsequently start to abrasively damage the contact area between a ball and the bearing race, resulting in a typical wear damage.  Because the damage has a similar look to brinelling, it was called false brinelling.<ref>{{Cite web|url=https://www.researchgate.net/publication/309585771|title=Service Life of Blade Bearings - Problems Faced in Service Life Estimation of Blade Bearings|last1=Schwack|first1=Fabian|last2=Poll|first2=Gerhard|website=ResearchGate|access-date=2017-06-27}}</ref>

[[File:Bike-Steering.png|thumb|Example of an application in which false brinelling may occur]]

Although the car-delivery problem has been solved, there are many modern examples.  A major maintenance problem are the pitch bearings in [[Wind turbine|wind turbines]], for which specialty greases had to be developed that result in almost no false brinelling damage.<ref>{{cite journal|last1=Schwack|first1=Fabian|title=Time-depending analyses of wear in oscillating bearings|journal=STLE|date=2017|issue=72nd|url=https://www.researchgate.net/publication/316543220}}</ref><ref>{{cite journal|last1=Stammler|first1=Matthias|title=Blade bearings: Damage mechanisms and test strategies|journal=CWD 2015|date=March 2015|pages=371–379|url=https://www.researchgate.net/publication/304789817}}</ref> Similar damage may also occur in electric and electronic contacts that are subjected to vibrations during use, think of aerospace and automotive connectors and even [[remote control]] battery compartments. Although the damage in these areas may not be as severe as the false brinelling in bearings, the damage mechanisms are similar and result in the creation of particles in the contact that can severely influence the electrical connection.

Also, [[Electrical generator|generator]]s or [[pump]]s may fail or need service because of this damage, so it is common to have a nearby spare unit which is left off most of the time but brought into service when needed. Surprisingly, however, vibration from the operating unit can cause bearing failure in the unit which is switched off. When that unit is turned on, the bearings may be noisy due to damage, and may fail completely within a few days or weeks<ref>{{cite journal|last1=Schwack|first1=Fabian|title=Comparison of Life Calculations for Oscillating Bearings Considering Individual Pitch Control in Wind Turbines|journal=Journal of Physics: Conference Series|volume=753|date=2016|issue=753|pages=11|doi=10.1088/1742-6596/753/11/112013|bibcode=2016JPhCS.753k2013S|doi-access=free}}</ref><ref>{{Cite book |url=https://www.tib.eu/en/search/id/tema:TEMA20130803793/False-brinelling-standstill-marks-on-roller-bearings/?tx_tibsearch_search%5Bsearchspace%5D=tn |title=False brinelling standstill marks on roller bearings |publisher=Technische Informationsbibliothek (TIB) |year=2011 |isbn=9783901657382 |access-date=2017-06-27}}</ref> even though the unit and its bearings are otherwise new.  Common solutions include: keeping the spare unit at a distance from the one which is on and vibrating; manually rotating shafts of the spare units on a regular (for example, weekly) basis; or regularly switching between the units so that both are in regular (for example, weekly) operation.

Until recently, bicycle [[Headset (bicycle part)|headsets]] tended to suffer from false brinelling in the "straight ahead" steering position, due to small movements caused by flexing of the fork.  Good modern headsets incorporate a [[plain bearing]] to accommodate this flexing, leaving the ball race to provide pure rotational movement.  {{Citation needed|date=April 2021|reason= PS- "Good modern" is very vague -- who makes them?  Modern as of what date?  I cannot think of a single example of a "modern bicycle headset" which contains a plain bearing in addition to the roller elements.  Campagnolo?  Wood?  Chris King?  FSA?  Cane Creek?}}

==References==
<references />

==External links==
* [https://web.archive.org/web/20080804102402/http://www.emersonbearing.com/fail_falsebrinell.htm Emerson Bearing picture of false Brinelling]
* [https://web.archive.org/web/20021208072751/http://precisionspindle.com/brinelling.htm Precision Spindle explanation of false Brinelling]
* [https://web.archive.org/web/20070927013920/http://www.mrotoday.com/mro/archives/Uptime/bearingAM03.htm MRO Today on rotating spares]
* [https://web.archive.org/web/20050412173757/http://www.usmotors.com/Service/Bulletins/Issue10-Sep03.pdf US Motors service bulletin case study, explanation, and pictures] (PDF)

{{DEFAULTSORT:False Brinelling}}
[[Category:Tribology]]
[[Category:Metallurgy]]
[[Category:Bearings (mechanical)]]