# Tribometer > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Tribometer > Markdown URL: https://mediated.wiki/source/Tribometer.md > Source: https://en.wikipedia.org/wiki/Tribometer > Source revision: 1329164197 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{short description|Instrument that measures friction and wear between surfaces}} {{Refimprove|date=April 2010}} thumb|335x335px|Pneumatic tribometer thumb|Static-friction tribometer|373x373px thumb|Hydrogen tribometer|334x334px A '''tribometer''' is an instrument that measures [tribological](/source/Tribology) quantities, such as [coefficient of friction](/source/coefficient_of_friction), friction force, and [wear](/source/wear) volume, between two surfaces in contact. It was invented by the 18th century [Dutch](/source/Netherlands) scientist [Musschenbroek](/source/Pieter_van_Musschenbroek)[https://books.google.com/books?id=RUQZPb4q-tkC&pg=PA210 Historic scientific instruments in Denmark]Hutton, Charles [http://archimedes.mpiwg-berlin.mpg.de/cgi-bin/archim/dict/hw?lemma=TRIBOMETER&step=entry&id=d006 A Mathematical and Philosophical Dictionary] {{Webarchive|url=https://web.archive.org/web/20110926233003/http://archimedes.mpiwg-berlin.mpg.de/cgi-bin/archim/dict/hw?lemma=TRIBOMETER&step=entry&id=d006 |date=2011-09-26 }} ''Tribotester'' is the general name given to a machine or device used to perform tests and simulations of wear, friction and [lubrication](/source/lubrication), which are the subject of the study of tribology.{{Citation needed|date=March 2018|reason=unclear if statement is based on widely-accepted definition. source should be stated.}} Often tribotesters are very specific in their function, fabricated by manufacturers to test and analyze the long-term performance of their products. An example is [orthopedic implant](/source/Implant_(medicine)) manufacturers, who develop tribotesters to accurately reproduce the motions and forces that occur in human [hip joint](/source/hip_joint)s for accelerated wear tests. ==Theory== thumb|334x334px A simple tribometer is described by a hanging mass and a mass resting on a horizontal surface, connected to each other via a string and pulley. The [coefficient of friction](/source/coefficient_of_friction), ''μ'', when the system is stationary, is determined by increasing the hanging mass until the moment that the resting mass begins to slide. Then using the general equation for friction force: :F = \mu N Where ''N'', the normal force, is equal to the weight (mass x gravity) of the sitting mass (''m''T) and ''F'', the loading force, is equal to the weight (mass x gravity) of the hanging mass (''m''H). To determine the kinetic coefficient of friction the hanging mass is increased or decreased until the mass system moves at a constant speed. In both cases, the coefficient of friction is simplified to the ratio of the two masses: :\mu\ = m_H / m_T In most test applications using tribometers, wear is measured by comparing the mass or surfaces of test specimens before and after testing. Equipment and methods used to examine the worn surfaces include [optical microscope](/source/optical_microscope)s, [scanning electron microscope](/source/scanning_electron_microscope)s, [optical interferometry](/source/optical_interferometry) and mechanical roughness testers. ==Types== Tribometers are often referred to by the specific contact arrangement they simulate or by the original equipment developer. Several arrangements are: * Four-ball{{cite journal |title=Evaluation of Several Space Lubricants Using a Vacuum Four-Ball Tribometer |journal=Tribology Transactions |volume=42 |issue=2 |pages=317–323 |doi=10.1080/10402009908982223 |year=1999 |last1=Jones |first1=William R. |last2=Poslowski |first2=Agnieszka K. |last3=Shogrin |first3=Bradley A. |last4=Herrera-Fierro |first4=Pilar |last5=Jansen |first5=Mark J. |hdl=2060/19990013975 |s2cid=137361318 |hdl-access=free }} * Pin-on-disc * Ball-on-disc * Ring-on-ring * Ball-on-three-plates * Reciprocating-pin (usually referred to as ''SRV or HFRR''){{Cite journal|last1=Wei|first1=D.P.|last2=Spikes|first2=H.A.|last3=Korcek|first3=S.|date=1999|title=The Lubricity of Gasoline|journal=Tribology Transactions|volume=42|issue=4|pages=813–823|doi=10.1080/10402009908982288}} * Block-on-ring * Bouncing-ball{{Cite journal | last1 = Höglund | first1 = Erik | title = The Relationship Between Lubricant Shear Strength and Chemical Composition of the Base Oil | journal = Wear | volume = 130 | pages = 213–224 | date = March 1989 | doi=10.1016/0043-1648(89)90234-2 }} * Fretting test machine * Twin-disc ===Bouncing-ball=== A ''[bouncing-ball](/source/bouncing_ball) tribometer'' consists of a ball which is impacted at an angle against a surface. During a typical test, a ball is slid on an angle along a track until it impacts a surface and then bounces off of the surface. The friction produced in the contact between the ball and the surface results in a horizontal force on the surface and a rotational force on the ball. Frictional force is determined by finding the rotational speed of the ball using high speed photography or by measuring the force on the horizontal surface. Pressure in the contact is very high due to the large instantaneous force caused by the impact with the ball. ''Bouncing-ball'' tribometers have been used to determine the shear characteristics of lubricants under high pressures such as is found in [ball bearings](/source/ball_bearings) or [gears](/source/gears). ===Pin-on-disc=== A ''pin-on-disc tribometer'' consists of a stationary pin that is normally loaded against a rotating disc. The pin can have any shape to simulate a specific contact, but cylindrical tips are often used to simplify the contact geometry. The coefficient of friction is determined by the ratio of the frictional force to the loading force on the pin. The pin-on-disc test has proved useful in providing a simple wear and friction test for low friction [coatings](/source/coatings) such as [diamond-like carbon](/source/diamond-like_carbon) coatings on [valve train](/source/valve_train) components in [internal combustion engine](/source/internal_combustion_engine)s. == See also == * [Abrasion](/source/Abrasion_(mechanical)) * [Twist compression tester](/source/Twist_compression_tester) * [Tribology](/source/Tribology) ==References== {{Reflist}} Category:Tribology Category:Measuring instruments Category:Materials science --- Adapted from the Wikipedia article [Tribometer](https://en.wikipedia.org/wiki/Tribometer) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Tribometer?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.