Tribology

TribologyFrom Wikipedia, the free encyclopedia

Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is a branch ofmechanical engineering and materials science.

Contents1 Etymology2 Fundamentals

2.1 Friction regimes3 History

3.1 Stribeck curve3.2 Jost Report3.3 New Areas of Tribology

4 Applications5 See also6 References7 Bibliography8 External links

EtymologyThe word tribology derives from the Greek root - of the verb , tribo, "I rub" in classic Greek; and the suffix -logy from -, -logia "study of", "knowledge of".

It was coined by the British physicist David Tabor,[1] and also by Peter Jost in 1964, a lubrication expert who noticed the problems with increasing friction on machines, and started the new discipline oftribology.[2]

FundamentalsThe tribological interactions of a solid surface's exposed face with interfacing materials and environment may result in loss of material from the surface. The process leading to loss of material is knownas "wear". Major types of wear include abrasion, friction (adhesion and cohesion), erosion, and corrosion. Wear can be minimized by modifying the surface properties of solids by one or more of "surfaceengineering" processes (also called surface finishing) or by use of lubricants (for frictional or adhesive wear).

Estimated direct and consequential annual loss to industries in the USA due to wear is approximately 1-2% of GDP. (Heinz, 1987). Engineered surfaces extend the working life of both original andrecycled and resurfaced equipment, thus saving large sums of money and leading to conservation of material, energy and the environment. Methodologies to minimize wear include systematicapproaches to diagnose the wear and to prescribe appropriate solutions. Important methods include:

Point like contact theory was established by Heinrich Hertz in 1880s.Fluid lubrication dynamics was established by Arnold Johannes Sommerfeld in 1900s.Terotechnology, where multidisciplinary engineering and management techniques are used to protect equipment and machinery from degradation (Peter Jost, 1972)Horst Czichos's systems approach, where appropriate material is selected by checking properties against tribological requirements under operating environment (H. Czichos,1978)Asset Management by Material Prognosis - a concept similar to terotechnology which has been introduced by the US Military (DARPA) for upkeep of equipment in good health and start-readycondition for 24 hours. Good health monitoring systems combined with appropriate remedies at maintenance and repair stages have led to improved performance, reliability and extended life cycleof the assets, such as advanced military hardware and civil aircraft.

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A typical Stribeck curve obtainedby Martens

Stribeck curve1. Solid/boundary friction2. Mixed friction3. Fluid friction

Tribological experimentssuggested by Leonardo da Vinci

In recent years, micro- and nanotribology have been gaining ground. Frictional interactions in microscopically small components are becoming increasingly important for the development of newproducts in electronics, life sciences, chemistry, sensors and by extension for all modern technology.

Friction regimes

Friction regimes for sliding lubricated surfaces have been broadly categorized into:

1. Solid/boundary friction2. Mixed friction3. Fluid friction

on the basis of the Stribeck curve. These curves clearly show the minimum value of friction as the demarcation between fullfluid-film lubrication and some solid asperity interactions.

Stribeck and others systematically studied the variation of friction between two liquid lubricated surfaces as a function of adimensionless lubrication parameter N/P, where is the dynamic viscosity, N the speed (e.g. revolutions per minute of a bearing)and P the load projected on to the geometrical surface.[3]

The Stribeck-curve has been a classic teaching element in tribology classes.[4]

History

Duncan Dowson surveyed the history of tribology in his book "History of Tribology (2nd edition)".[5] This comprehensive book covers developments from prehistory,though early civilizations (Mesopotamia, Egypt) and finally the key developments up to the end of the previous century.

Historically, Leonardo da Vinci (14521519) was the first to enunciate two laws of friction.[6] (It was this connection that gave the name to the Leonardo Centre forTribology (http://www.leonardocentre.co.uk/), one of the UK's leading research centres on the subject.) According to da Vinci, the frictional resistance was the same fortwo different objects of the same weight but making contacts over different widths and lengths. He also observed that the force needed to overcome friction doubleswhen the weight doubles. da Vinci's findings remained unpublished in his notebooks.[7][8]

Guillaume Amontons rediscovered the classic rules (1699). They were further developed by Charles-Augustin de Coulomb (1785).

Charles Hatchett (17601820) carried out the first reliable test on frictional wear using a simple reciprocating machine to evaluate wear on gold coins. He found thatcompared to self-mated coins, coins with grits between them wore at a faster rate.

Stribeck curve

The "Stribeck curve" or "StribeckHersey curve" (named after Richard Stribeck,[9][10][11] who heavily documented and established examples of it, and Mayo D. Hersey[12][13]), used to categorize thefriction properties between two surfaces, was developed in the first half of the 20th century. The research of Professor Richard Stribeck (18611950) was performed in Berlin at the Royal PrussianTechnical Testing Institute (MPA, now BAM). Similar work was previously performed around 1885 by Prof. Adolf Martens (18501914) at the same Institute and in the mid-1870s by Dr. Robert H. Thurston[14][15] at the Stevens Institute of Technology in the U.S. Prof. Dr. Thurston was therefore close to establishing the Stribeck curve, but he presented no Stribeck-like graphs, as he evidently did notfully believe in the relevance of this dependency. Since that time the Stribeck-curve has been a classic teaching element in tribology classes.[4]

The graphs of friction force reported by Stribeck stem from a carefully conducted, wide-ranging series of experiments on journal bearings. Stribeck systematically studied the variation of friction betweentwo liquid lubricated surfaces.[3] His results were presented on 5 December 1901 during a public session of the railway society and published on 6 September 1902. They clearly showed the minimumvalue of friction as the demarcation between full fluid-film lubrication and some solid asperity interactions. Stribeck studied different bearing materials and aspect ratios D/L from 1:1 to 1:2. The maximumsliding speed was 4 m/s and the geometrical contact pressure was limited to 5 MPa. (These operating conditions were related to railway wagon journal bearings.)



The reason why the form of the friction curve for liquid lubricated surfaces was later attributed to Stribeck, although both Thurston and Martens achieved their results considerably earlier, (Martens evenin the same organization roughly 15 years before), may be because Stribeck published in the most important technical journal in Germany at that time, Zeitschrift des Vereins Deutscher Ingenieure (VDI,Journal of German Mechanical Engineers). Martens published his results only in the official journal of the Royal Prussian Technical Testing Institute, which has now become BAM. The VDI journal, asone of the most important journals for engineers, provided wide access to these data and later colleagues rationalized the results into the three classical friction regimes. Thurston however, did not havethe experimental means to record a continuous graph of the coefficient of friction but only measured the friction at discrete points; this may be the reason why the minimum in the coefficient of frictionwas not discovered by him. Instead, Thurston's data did not indicate such a pronounced minimum of friction for a liquid lubricated journal bearing as was demonstrated by the graphs of Martens andStribeck.

Jost Report

The term tribology became widely used following The Jost Report in 1966. The report said that friction, wear and corrosion were costing the UK huge sums of money every year. As a result, the UK setup several national centres for tribology. Since then the term has diffused into the international engineering field, with many specialists now claiming to be tribologists.

There are now numerous national and international societies, such as the Society for Tribologists and Lubrication Engineers (STLE (http://www.stle.org)) in the USA, the Institution of MechanicalEngineers' Tribology Group (IMechE Tribology Group (http://www.imeche.org/knowledge/industries/tribology/overview)) in the UK or the German Society for Tribology (Gesellschaft fr Tribologie, www.gft-ev.de) and MYTRIBOS[16] (Malaysian Tribology society).

Most technical universities have researchers working on tribology, often as part of mechanical engineering departments. The limitations in tribological interactions are, however, no longer mainlydetermined by mechanical designs, but by material limitations. So the discipline of tribology now counts at least as many materials engineers, physicists and chemists as it does mechanical engineers.

New Areas of Tribology

Since the 1990s, new areas of tribology have emerged, including the nanotribology, biotribology, and green tribology. These interdisciplinary areas study the friction, wear and lubrication at the nanoscale(including the Atomic force microscopy and micro/nanoelectromechanical systems, MEMS/NEMS), in biomedical applications (e.g., human joint prosthetics, dental materials), and ecological aspects offriction, lubrication and wear (tribology of clean energy sources, green lubricants, biomimetic tribology).

ApplicationsThe study of tribology is commonly applied in bearing design but extends into almost all other aspects of modern technology, even to such unlikely areas as hair conditioners and cosmetics such aslipstick, powders and lipgloss.

Any product where one material slides or rubs over another is affected by complex tribological interactions, whether lubricated like hip implants and other artificial prostheses, or unlubricated as in hightemperature sliding wear in which conventional lubricants cannot be used but in which the formation of compacted oxide layer glazes have been observed to protect against wear.

Tribology plays an important role in manufacturing. In metal-forming operations, friction increases tool wear and the power required to work a piece. This results in increased costs due to more frequenttool replacement, loss of tolerance as tool dimensions shift, and greater forces required to shape a piece. The use of lubricants which minimize direct surface contact reduces tool wear and powerrequirements.[citation needed]

See alsoBearingsContact mechanicsEnergetically modified cementFrettingFrictionGalling

List of tribology organizationsLubricationOil additiveOil analysisSpace tribologySurface science

TribocorrosionTribometerWearWettingTribology in Malaysia (https://sites.google.com/site/tribologyinmalaysia/)

References



^ Field, J. (2008). "David Tabor. 23 October 1913 -- 26 November2005". Biographical Memoirs of Fellows of the Royal Society 54:425459. doi:10.1098/rsbm.2007.0031 (http://dx.doi.org/10.1098%2Frsbm.2007.0031).

1.

^ Mitchell, Luke (November 2012). "The Fiction of Nonfriction". InWard, Jacob. Popular Science. No. 5 281 (November 2012): 40.

2.

^ a b R. Stribeck, Die wesentlichen Eigenschaften der Gleit- undRollenlager (The basic properties of sliding and rolling bearings),Zeitschrift des Vereins Deutscher Ingenieure, 2002, Nr. 36, Band46, p. 1341-1348, p. 1432-1438 and 1463-1470

3.

^ a b H. Czichos, K.-H. Habig, Tribologie-Handbuch (Tribologyhandbook), Vieweg Verlag, Wiesbaden, 2nd edition, 2003, ISBN3-528-16354-2

4.

^ Duncan Dowson, History of Tribology, Second Edition,Professional Engineering Publishing, 1997, ISBN 1-86058-070-X

5.

^ Palaci, Ismal (2007), Atomic Force Microscopy Studies ofNanotribology and Nanomechanics. p. 52. (http://biblion.epfl.ch/EPFL/theses/2007/3905/EPFL_TH3905.pdf)

6.

^ Armstrong-Hlouvry, Brian (1991). Control of machines withfriction (http://books.google.com/?id=0zk_zI3xACgC&pg=PA10).USA: Springer. p. 10. ISBN 0-7923-9133-0.

7.

^ van Beek, Anton. "History of Science Friction"(http://www.tribology-abc.com/abc/history.htm). tribology-abc.com.Retrieved 2011-03-24.

8.

^ Stribeck, R. (1901), Kugellager fr beliebige Belastungen (BallBearings for any Stress), Zeitschrift des Vereins DeutscherIngenieure 45.

9.

^ Stribeck, R. (1902), Die wesentlichen Eigenschaften der Gleit- undRollenlager (Characteristics of Plain and Roller Bearings), Zeit. desVDI 46.

10.

^ Jacobson, Bo (2003), The Stribeck memorial lecture.(http://www.sciencedirect.com/science?_ob=ArticleURL&

11.

_udi=B6V57-497HBKM-4&_user=10&_coverDate=11%2F30%2F2003&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1433619808&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=634f43c7420d0709195dbd4ac5e8a719)^ Hersey, M. D. (1914), The Laws of Lubrication of HorizontalJournal Bearings, J. Wash. Acad. Sci., 4, 542-552.

12.

^ Biography of Mayo D. Hersey (http://www.nndb.com/people/221/000169711/)

13.

^ Robert H. Thurston, Friction and lubrication - Determination of thelaws and co-fficients of friction by new methods and with newapparatus, Trbner and Co., Ludgate Hill, London, 1879

14.

^ Robert H. Thurston, A treatise on friction and lost work inmachinery and millwork, John Wiley&Sons, New York, 1894, fifthedition

15.

^ http://mytribos.org/wp/16.

BibliographySurface Wear Analysis, Treatment, and Prevention: R. Chattopadhyay, published by ASM-International, Materials Park, OH, 2001, ISBN 0-87170-702-0.Advanced Thermally Assisted Surface Engineering Processes: Ramnarayan Chattopadhyay, Kluwer Academic Publishers, MA (now Springer, NY), 2004.DeGarmo, E. Paul, J T. Black, and Ronald A. Kohser. Materials and Processes in Manufacturing. Upper Saddle River, New Jersey: Prentice Hall, 1997. ISBN 0-02-328621-0Zum Gahr, Karl-Heinz (1987). Microstructure and Wear of Materials. Tribology Series, 10. Elsevier. ISBN 0-444-42754-6.Heshmat, Hooshang. Tribology of Interface Layers. CRC Press. ISBN 978-0-8247-5832-5.Litt, Fred. "Starting from Scratch: Tribology Basics Volume I" (http://www.stle.org/assets/document/Starting_from_Scratch.pdf). STLE. Retrieved 2010-06-10.

External linksInternational Tribology Council (http://www.itctribology.org/)Tribology NL (http://www.tribology-abc.com/default.htm) an overview of tribology topics targeted at mechanical engineers.IET Tribology Network (http://mycommunity.theiet.org/communities/home/69?origin=wikipedia)Leonardo Centre for Tribology, University of Sheffield (http://www.leonardocentre.co.uk/)National Centre for Advanced Tribology (nCATS), University of Southampton (http://www.southampton.ac.uk/ncats/)

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