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Fretting
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<h2 id="materials">Materials</h2> <h3>Steel</h3> <p>Fretting damage in <a href="/facts/Steel/aN6qWo4H">steel</a> can be identified by the presence of a pitted surface and fine 'red' iron oxide dust resembling cocoa powder. Strictly this debris is not '<a href="/facts/Rust/sajUmaz8">rust</a>' as its production requires no water. The particles are much harder than the steel surfaces in contact, so <a href="/facts/Abrasive_wear/2PxRQ1Ke">abrasive wear</a> is inevitable; however, particulates are not required to initiate fret. </p> <h3>Aluminium</h3> <p>Fretting in Aluminium causes black debris to be present in the contact area due to the fine oxide particles. </p> <h2 id="products-affected">Products affected</h2> <p>Fretting examples include wear of drive <a href="/facts/Spline_(mechanical)/Pa66LVGv">splines</a> on <a href="/facts/Driveshaft/lHnhqzzT">driveshafts</a>, wheels at the <a href="/facts/Lug_nut/be9DY4qF">lug bolt</a> interface, and <a href="/facts/Cylinder_head/K0RJ8mxT">cylinder head</a> <a href="/facts/Gasket/gQ3bnuPK">gaskets</a> subject to differentials in <a href="/facts/Thermal_expansion/BP2vjX0N">thermal expansion</a> coefficients. </p><p>There is currently a focus on fretting research in the aerospace industry.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> The dovetail blade-root connection and the spline coupling of gas turbine aero engines experience fretting.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p><p>Another example in which fretting corrosion may occur are the pitch <a href="/facts/Bearing_(mechanical)/Tb8HmHWt">bearings</a> of modern <a href="/facts/Wind_turbine/lUfWqfLg">wind turbines</a>, which operate under oscillation motion to control the power and loads of the turbine.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>Fretting can also occur between reciprocating elements in the human body. Especially implants, for example hip implants, are often affected by fretting effects.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="fretting-electricalelectronic-connectors">Fretting electrical/electronic connectors</h2> <p>Source:<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>Fretting also occurs on virtually all electrical connectors subject to motion (e.g. a printed circuit board connector plugged into a backplane, i.e. SOSA/<a href="/facts/VPX/oLMfczJt">VPX</a>). Commonly most <a href="/facts/Board-to-board_connector/hRY3eN6W">board to board</a> (B2B) electrical connectors are especially vulnerable if there is any relative motion present between the mating connectors. A mechanically rigid connection system is required to hold both halves of a B2B motionless (often impossible). Wire to board (W2B) connectors tend to be immune to fretting because the wire half of the connector acts as a spring absorbing relative motion that would otherwise transfer to the contact surfaces of the W2B connector. Very few exotic B2B connectors exist that address fretting by: 1) incorporating springs into the individual contacts or 2) using a Chinese finger trap design to greatly increase the contact area. A connector design that contacts all 4-sides of a square pin instead of just one or 1 or 2 can delay the inevitable fretting some amount. Keeping contacts clean and lubricated also offers some longevity. </p><p>Contact fretting can change the <a href="/facts/Electrical_impedance/I06NSXtN">impedance</a> of a B2B connector from milliohms to ohms in just minutes when vibration is present. The relatively soft and thin gold plating used on most high quality electrical connectors is quickly worn through exposing the underlying alloy metals and with fretting debris the impedance rapidly increases. Somewhat counterintuitively, high contact forces on the mated connector pair (thought to help lower impedance and increase reliability) can actually make the rate of fretting even worse. </p> <h2 id="fretting-in-rolling-element-bearings">Fretting in rolling element bearings</h2> <p>In rolling element bearings fretting may occur when the bearings are operating in an oscillating motion. Examples of applications are blade bearings in wind turbines, helicopter rotor pitch bearings, and bearings in robots. If the bearing movement is limited to small motions the damage caused may be called fretting or <a href="/facts/False_brinelling/cJcYQYUx">false brinelling</a> depending on mechanism encountered.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> The main difference is that false brinelling occurs under lubricated and fretting under dry contact conditions. Between false brinelling and fretting corrosion, a time-dependent relation has been proposed.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="fretting-fatigue">Fretting fatigue</h2> <p>Fretting decreases <a href="/facts/Fatigue_(material)/zmJY8hMt">fatigue</a> strength of materials operating under cycling stress. This can result in <i>fretting fatigue</i>, whereby fatigue cracks can initiate in the fretting zone. Afterwards, the crack propagates into the material. Lap joints, common on airframe surfaces, are a prime location for fretting corrosion. This is also known as frettage or fretting corrosion.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="factors-affecting-fretting">Factors affecting fretting</h2> <p>Fretting resistance is not an intrinsic property of a material, or even of a material couple. There are several factors affecting fretting behavior of a contact:<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <ul><li>Contact load</li> <li>Sliding amplitude</li> <li>Number of cycles</li> <li>Temperature</li> <li>Relative humidity</li> <li>Inertness of materials</li> <li>Corrosion and resulting motion-triggered contact insufficiency</li></ul> <h2 id="mitigation">Mitigation</h2> <p>The fundamental way to prevent fretting is to design for no relative motion of the surfaces at the contact. <a href="/facts/Surface_roughness/o35uJjc4">Surface roughness</a> plays an important role as fretting normally occurs by the contact of the <a href="/facts/Asperity_(materials_science)/SBCHaJPL">asperities</a> of the mating surfaces. <a href="/facts/Lubricant/9PXISDwU">Lubricants</a> are often employed to mitigate fretting because they reduce <a href="/facts/Friction/d0108Rpu">friction</a> and inhibit oxidation. This may however, also cause the opposite effect as a lower coefficient of friction may lead to more movement.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> Thus, a solution must be carefully considered and tested. In the aviation industry, coatings are applied to cause a harder surface and/or influence the friction coefficient. </p><p>Soft materials often exhibit higher susceptibility to fretting than hard materials of a similar type. The <a href="/facts/Hardness/PtGn6E20">hardness</a> ratio of the two sliding materials also has an effect on fretting wear.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> However, softer materials such as <a href="/facts/Polymer/eF32E50K">polymers</a> can show the opposite effect when they capture hard debris which becomes embedded in their bearing surfaces. They then act as a very effective <a href="/facts/Abrasive/UJ9TvVMx">abrasive</a> agent, wearing down the harder metal with which they are in contact. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Contact_mechanics/oKVrqJxL">Contact mechanics</a> – Study of the deformation of solids that touch each other</li> <li><a href="/facts/Motion-triggered_contact_insufficiency/LDvtMctl">Motion-triggered contact insufficiency</a> – Wear or damage on loaded surfacesPages displaying short descriptions of redirect targets</li> <li><a href="/facts/Tribology/13JNgmhS">Tribology</a> – Science of rubbing surfaces</li> <li><a href="/facts/Wear/2PxRQ1Ke">Wear</a> – Damaging, gradual removal or deformation of material at solid surfaces</li></ul> <h2 id="external-links">External links</h2> Wikimedia Commons has media related to Fretting corrosion. <ul><li><a href="http://www.epi-eng.com/mechanical_engineering_basics/fretting_corrosion.htm">Fretting and Its Insidious Effects, by EPI Inc.</a></li> <li><a href="https://www.aac-research.at/wp-content/uploads/2023/01/ESA-STM279.pdf">Assessment Of Cold Welding Between Separable Contact Surfaces Due To Impact And Fretting Under Vacuum</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>ASM Handbook, Vol. 13 "Corrosion", ASM International, 1987. <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Rao, D. Srinivasa; Krishna, L. Rama; Sundararajan, G. (2017). "Detonation Sprayed Coatings for Aerospace Applications". Aerospace Materials and Material Technologies. Indian Institute of Metals Series. Springer, Singapore. pp. 483–500. doi:10.1007/978-981-10-2134-3_22. ISBN 978-981-10-2133-6. <a href="978-981-10-2133-6" target="_blank">978-981-10-2133-6</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Govindarajan Narayanan (2016-10-03). "Effect of sliding friction on spline surface failure under misaligned condition in aero engines". International Journal of Structural Integrity. 7 (5): 617–629. doi:10.1108/IJSI-07-2015-0024. ISSN 1757-9864. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Schwack, Fabian (2016). "Comparison of Life Calculations for Oscillating Bearings Considering Individual Pitch Control in Wind Turbines". Journal of Physics: Conference Series. 753 (11): 112013. Bibcode:2016JPhCS.753k2013S. doi:10.1088/1742-6596/753/11/112013. Retrieved 2016-03-23. <a href="https://www.researchgate.net/publication/308749203" target="_blank">https://www.researchgate.net/publication/308749203</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Molloy, Dennis O.; Munir, Selin; Jack, Christopher M.; Cross, Michael B.; Walter, William L.; Walter, William K. (2014-03-19). "Fretting and corrosion in modular-neck total hip arthroplasty femoral stems". The Journal of Bone and Joint Surgery. American Volume. 96 (6): 488–493. doi:10.2106/JBJS.L.01625. ISSN 1535-1386. PMID 24647505. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Brown, L; Zhang, H; Blunt, L; Barrans, S (2007-08-01). "Reproduction of fretting wear at the stem—cement interface in total hip replacement" (PDF). Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 221 (8): 963–971. doi:10.1243/09544119JEIM333. ISSN 0954-4119. PMID 18161257. S2CID 7918311. <a href="http://eprints.hud.ac.uk/id/eprint/817/1/BroReproduction.pdf" target="_blank">http://eprints.hud.ac.uk/id/eprint/817/1/BroReproduction.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Braunovic, Milenko (2009). "Fretting in Electrical/Electronic Connections: A Review". IEICE Transactions on Electronics. E92-C (8): 982–991. Bibcode:2009IEITE..92..982B. doi:10.1587/transele.E92.C.982. ISSN 0916-8524. <a href="http://www.jstage.jst.go.jp/article/transele/E92.C/8/E92.C_8_982/_article" target="_blank">http://www.jstage.jst.go.jp/article/transele/E92.C/8/E92.C_8_982/_article</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Godfrey, Douglas (2003). "Fretting corrosion or false brinelling?" (PDF). Tribology and Lubrication Technology. 59 (12): 28–31. Retrieved 2017-06-23. <a href="https://www.stle.org/images/pdf/STLE_ORG/BOK/LS/Bearings/Fretting%20Corrosion%20or%20False%20Brinelling_tlt%20article_Dec03.pdf" target="_blank">https://www.stle.org/images/pdf/STLE_ORG/BOK/LS/Bearings/Fretting%20Corrosion%20or%20False%20Brinelling_tlt%20article_Dec03.pdf</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Errichello, Robert (2004). "Another perspective: false brinelling and fretting corrosion". Tribology & Lubrication Technology. 60 (4): 34–36. Retrieved 2017-06-23. <a href="https://www.researchgate.net/publication/286233368" target="_blank">https://www.researchgate.net/publication/286233368</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Schwack, Fabian. "Time-dependet analyses of wear in oscillting bearing applications". STLE. 72nd. Retrieved 2017-06-23. <a href="https://www.researchgate.net/publication/316543220" target="_blank">https://www.researchgate.net/publication/316543220</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Charles Lipson, Lester Vern Colwell; Handbook of mechanical wear: wear, frettage, pitting, cavitation, corrosion; University of Michigan Press, 1961; p. 449. <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Aydar, Akchurin (16 March 2019). "Fretting, fretting corrosion and fretting mechanisms". <a href="http://www.tribonet.org/wiki/fretting/" target="_blank">http://www.tribonet.org/wiki/fretting/</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>ASM Handbook, Vol. 19 "Fatigue and Fracture Handbook", ASM International, 1996. <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>A. Neyman, O. Olszewski, "Research on fretting wear dependence of hardness ratio and friction coefficient of fretted couple", Wear of materials, International conference No. 9, San Francisco CA, USA (13/04/1993). Wear, vol. 162-64, Part B, pp. 939-943, 1993. <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> </ol>