Fretting refers to wear and sometimes corrosion damage at the asperities of contact surfaces. This damage is induced under load and in the presence of repeated relative surface motion, as induced for example by vibration. The ASM Handbook on Fatigue and Fracture defines fretting as: "A special wear process that occurs at the contact area between two materials under load and subject to minute relative motion by vibration or some other force." Fretting tangibly degrades the surface layer quality producing increased surface roughness and micropits, which reduces the fatigue strength of the components.
The contact movement causes mechanical wear and material transfer at the surface, often followed by oxidation of both the metallic debris and the freshly exposed metallic surfaces. Because the oxidized debris is usually much harder than the surfaces from which it came, it often acts as an abrasive agent that increases the rate of fretting.
The distinction between false brinelling and fretting corrosion has been extensively discussed in the literature. The main difference is that false brinelling occurs under lubricated and fretting under dry contact conditions. Between false brinelling and fretting corrosion also exists a time-dependent connection.
Fretting damage in steel can be identified by the presence of a pitted surface and fine 'red' iron oxide dust resembling cocoa powder. Strictly this debris is not 'rust' as its production requires no water. The particles are much harder than the steel surfaces in contact, so abrasive wear is inevitable; however, particulates are not required to initiate fret.
Fretting decreases fatigue strength of materials operating under cycling stress. This can result in fretting fatigue, 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.
Factors affecting fretting
- Contact load
- Sliding Amplitude
- Number of cycles
- Relative humidity
- Inertness of materials
The fundamental way to prevent fretting is to design for no relative motion of the surfaces at the contact. Surface roughness plays an important role as fretting normally occurs by the contact of the asperities of the mating surfaces. Lubricants are often employed to mitigate fretting because they reduce friction and inhibit oxidation.
Soft materials often exhibit higher susceptibility to fretting than hard materials of a similar type. The hardness ratio of the two sliding materials also has an effect on fretting wear. However, softer materials such as polymers can show the opposite effect when they capture hard debris which becomes embedded in their bearing surfaces. They then act as a very effective abrasive agent, wearing down the harder metal with which they are in contact.
- ASM Handbook, Vol. 13 "Corrosion", ASM International, 1987.
- Godfrey, Douglas (2003). "Fretting corrosion or false brinelling?" (PDF). Ribology and Lubrication Technology. 59 (12): 28–31. Retrieved 2017-06-23.
- Errichello, Robert (2004). "Another perspective: false brinelling and fretting corrosion". Tribology & Lubrication Technology. 60 (4): 34–36. Retrieved 2017-06-23.
- Schwack, Fabian. "Time-dependet analyses of wear in oscillting bearing applications". STLE. 72th. Retrieved 2017-06-23.
- 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.
- 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.
- 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. doi:10.1088/1742-6596/753/11/112013. Retrieved 2016-03-23.
- 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.
- 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.
- Charles Lipson, Lester Vern Colwell; Handbook of mechanical wear: wear, frettage, pitting, cavitation, corrosion; University of Michigan Press, 1961; p. 449.
- Aydar, Akchurin. "Fretting, fretting corrosion and fretting mechanisms".
- 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.
|Wikimedia Commons has media related to Fretting corrosion.|