Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > New nano-measurements add spark to centuries-old theory of friction

Abstract:
The phenomenon of friction, when studied on a nanoscale, is more complex than previously thought. When friction occurs, an object does not simply slide its surface over that of another, it also makes a slight up-and-down movement. This finding completes a centuries-old theory of friction dating to 1699 and uncovers a gap in contemporary thinking on friction. The phenomenon - termed lift-up hysteresis - was described in a recent study by researchers Farid Al-Bender, Kris De Moerlooze and Paul Vanherck of the Production Engineering, Machine Design and Automation Division at KU Leuven's Department of Mechanical Engineering.

New nano-measurements add spark to centuries-old theory of friction

Leuven, Belgium | Posted on March 27th, 2012

Friction is the force that occurs when one surface slides over another, or when an object moves through a liquid or a gas. Until now, the theory explaining the phenomenon of friction was fragmented. French physicists Guillaume Amontons and Charles August Coulomb, working in the late-17th and mid-18th centuries, respectively, strove to find an explanation for frictional resistance. Frictional resistance explains, for instance, why gliding a heavy cabinet across a floor is much more difficult than gliding a chair. As the weight of an object increases, so too does the resistance. The floor and the bottom of the cabinet move against one another from left to right or vice versa. But at the same time the weight of the cabinet bears perpendicularly upon the bottom of the cabinet and the floor. This normal load - 'normal' in the sense of being perpendicular to the direction of shifting - pushes the two surfaces together and produces resistance as friction occurs. If we put the chair and the cabinet on wheels and push them uphill, more force is needed to move the cabinet than to move the chair.

Using this reasoning, Amontons and Coulomb explained friction by the roughness of both surfaces: the (sometimes microscopically small) nooks and crannies of one surface - asperities - which settle upon those of another when one object rests upon another. When friction occurs, these asperities play the role of slopes. They are made to climb, descend and deform so that movement can continue, similar to what happens when the bristles of two brushes rub together. This theory is sometimes called the ‘bump hypothesis' because one surface grinds over the bumps of another with an up-and-down movement.

In the 20th century it became clear that the existing theory did not fully correspond with the laws of thermodynamics, the science that studies the conversion of heat into mechanical energy or vice versa. Specifically, Amontons and Coulomb's bump hypothesis failed to explain energy lost as a result of friction. In their theory, the sum of the energy needed to go 'uphill' and then 'downhill' is zero. At the same time, we know that pure surfaces have an electro-chemical tendency to stick to each other. This is caused by asperities being stuck to one another in a phenomenon called adhesion. A typical example is Scotch tape. When movement occurs, all the bonds between the asperities of the two surfaces are broken and reformed elsewhere. Consequently, factors such as speed and acceleration influence friction. With the rise of the newer adhesion theory, Amontons and Coulomb's theory gradually faded into oblivion. But the modern adhesion theory of friction was shown to have inconsistencies of its own.

Normal motion, nano-scale

Micro- and nano-scale measurement techniques now allow researchers to study friction at an atomic level. Professor Farid Al-Bender and his team conducted an experiment with extremely precise friction and displacement sensors and tested various materials (paper, plastic and brass) at different speeds of movement. The results map out frictional force measurements consistent with those predicted by adhesion theory. But until now, 'normal motion' - movement perpendicular to the rubbing movement - had not yet been measured. While normal motion amounts to a mere 5 - 50 nanometers - billionths of a meter - this systematic up-and-down motion had previously been overlooked. Measurements of this normal motion, say the KU Leuven researchers, confirms the centuries-old hypothesis of asperity deformation and slope pioneered by Amontons and Coulomb and paints a more complex picture of the phenomenon of friction because normal motion must now be taken into account when developing a comprehensive theory of friction. Al-Bender and his team's results suggest that friction is caused by an interaction of both adhesion on the one hand and asperity deformation and slope on the other.

Tribology

Tribology - the science of friction, lubrication and wear - is an important area of mechanical engineering. Tribology research can help lower economic and environmental costs of production and usage. If the interaction between moving surfaces can be controlled, time and energy inputs can be optimised and wear-and-tear, malfunctions and waste can be reduced. Tribology research can also contribute to the miniaturisation of products, such as computer components. At KU Leuven, research in tribology is closely linked with research in mechanical engineering, machine design, materials science and robotics.

Full bibliographic informationFarid Al-Bender, Kris De Moerlooze and Paul Vanherck, Lift-up Hysteresis Butterflies in Friction, Tribology Letters
Volume 46, Number 1, 23-31, DOI: 10.1007/s11249-012-9914-y.

####

For more information, please click here

Contacts:
Griet Van der Perre
+32 16 32 40 08


Professor Farid Al-Bender
Production Engineering
Machine Design and Automation Division
Department of Mechanical Engineering
KU Leuven

Copyright © AlphaGalileo

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Read more:

Related News Press

News and information

GLOBALFOUNDRIES and Soitec Enter Into Long-term Supply Agreement on FD-SOI Wafers: Strategic milestone to help guarantee a secure, high-volume supply of FD-SOI technology September 20th, 2017

GLOBALFOUNDRIES Announces Availability of mmWave and RF/Analog on Leading FDX™ FD-SOI Technology Platform: Technology solution delivers ‘connected intelligence’ to next generation high-volume wireless and IoT applications with lower power and significantly reduced cost September 20th, 2017

GLOBALFOUNDRIES Announces Availability of Embedded MRAM on Leading 22FDX® FD-SOI Platform: Advanced embedded non-volatile memory solution delivers ‘connected intelligence’ by expanding SoC capabilities on the 22nm process node September 20th, 2017

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Physics

New quantum phenomena in graphene superlattices September 18th, 2017

Bit data goes anti-skyrmions September 1st, 2017

Heating quantum matter: A novel view on topology: Physicists demonstrate how heating up a quantum system can be used as a universal probe for exotic states of matter August 22nd, 2017

Sensing technology takes a quantum leap with RIT photonics research: Office of Naval Research funds levitated optomechanics project August 10th, 2017

Discoveries

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

New quantum phenomena in graphene superlattices September 18th, 2017

Announcements

GLOBALFOUNDRIES Delivers 8SW RF SOI Technology for Next-Generation Mobile and 5G Applications: Advanced 8SW 300mm SOI technology enables cost-effective, high-performance RF front-end modules for 4G LTE mobile and sub-6GHz 5G applications September 20th, 2017

GLOBALFOUNDRIES Unveils Vision and Roadmap for Next-Generation 5G Applications: Technology platforms are uniquely positioned to enable a new era of ‘connected intelligence’ with the transition to 5G September 20th, 2017

GLOBALFOUNDRIES Delivers Custom 14nm FinFET Technology for IBM Systems: Jointly developed 14HP process is world’s only technology that leverages both FinFET and SOI September 20th, 2017

GLOBALFOUNDRIES Introduces New 12nm FinFET Technology for High-Performance Applications September 20th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project