Can full film occur when Lambda = 0.6?

The holy grail of tribologists studying lubricated systems is often to predict the contact lifespan. For this purpose, you can compute the minimum film thickness separating the two bodies… but only if you make the assumption that the body surfaces are perfectly flat! This is obviously never the...Read More »

How to get cited!

After years of research, problem solving and brain storming the fact that a fellow researcher found your work helpful in his own research is so fulfilling. This makes citing one of the most important factors that determines the impact of a research paper in its respective field. In...Read More »

Nanoscale friction on thin films

In nature ‘entities’, either be living or non-living tend to behave differently at different scales by exhibiting different properties. Which play a major role in the way we frame our perspectives and opinions on them. One of the simplest examples is watching an airplane soaring in sky and...Read More »

How to make greener ammonia with tribology?

A bit of context

Ammonia synthesis is estimated to generate ~1% of the world CO2 emissions [2]. This single molecule is mass produced (~175 Mt) and the Haber-Bosch process employed is fossil fuel hungry! High pressure, high temperature and natural gas are required in this process. You...Read More »

The physics behind ice skating: A tribological perspective

Ever wondered what makes ice so special to skate on it? Apart from freezing your favorite beverages, it helps make life adventurous. Yes, I am talking about sports like ice skating and ice hockey, it’s amusing when you think that there are national level sports leagues...Read More »

What is this device?

What if the bearings in the wheels of your future car/bicycle/motorbike was doing more than the normal bearing job? What if it could not only bear the load with minimum friction, but also insure other functionalities? To be honest, it is already the case as wheel hub bearings also...Read More »

Introduction to Sealing Technology

Let’s start from the beginning: what is a seal?

A device or material that is used to close off or fasten an opening or connection, especially to prevent the escape of a liquid or gas.

In other words, a seal is a mechanical component used for keeping the fluid A and the...Read More »

Illusion of static friction: Does it really exist?

Static friction might be an illusion made by the rotation of kinetic friction, even though, since the time of Charles-Augustin de Coulomb (1736–1806), we have believed that there exist two types of solid friction. Nakano and Popov [1] analyzed numerically and theoretically...Read More »

How to better predict the minimum film thickness of elastohydrodynamic contacts?

Let’s say you have the choice between an almost infinite lifespan device, and a device that undergoes wear and failure within a few minutes or hours of running. In most cases, you would choose the former and discard the latter. Let’s say that this device is a rolling element bearing...Read More »

Programmable Friction: Electrical Regulation of Ionic Liquid Lubrication

Friction is a force rising between two surfaces when they move in opposite directions or when one moves over a stationary surface. The scale of the movement does not matter: from the movement of continental plates and glaciers to the motion of the atoms, friction forces...Read More »

Electric vehicles: less challenges for tribologists?

The article was created by Dr. Jean-David Wheeler, Engineer in modeling at SIMTEC

With the last years’ rise of electric vehicles (EV), you may have thought that the future lubrication challenges for cars may not be...Read More »

Solving the Problem of Slippery Train Tracks Due to Fallen Leaves

Friction is the force experienced when two surfaces slide, or try to slide, across each other. We are thankful for friction when we put our foot on the brake to stop the car, or when we are walking down the sidewalk. However, friction is often seen...Read More »

An ingenious work on contact mechanics by Föppl and Schubert went into oblivion due to the Second World War

The history of science sometimes reads like a detective novel. The personal destinies sometimes lead to the fact that outstanding, ingenious works which were decades ahead of their time, sink into oblivion. This seems to have happened with the publications of Föppl (1941) and Schubert (1942) on contact...Read More »

Measuring viscosity in the Earth's Mantle

The earth seems to be fairly solid as we stand on its surface. We stand on solid ground and do not sink through the floors in our homes. However, underneath that solid-looking crust are layers where the rock is a liquid because the surroundings are that hot. Underneath...Read More »

Minimal Quantity Lubrication: Drop on Demand Printing Technique

The article was written by Dr. Aydar Akchurin

Recent research ( has shown that about 23% of the world’s total energy consumption comes from the tribological contacts (moving parts subject to friction and wear, such as...Read More »

Slow-Moving Earthquakes

The scientific theory of plate tectonics (a word derived from the Greek word tectonicus which means ‘pertains to building’) describes the large-scale motion of the seven or eight major plates (the number depends on how the plates are defined) in the Earth’s lithosphere and the movement of the...Read More »

Future of Oil Analysis is Linked to Machine Learning

Traditional oil analysis, also called oil condition monitoring (OCM) analyzes samples for abnormal wear, condition of the fluid, and presence of contaminates. The presence of any of these issues indicates that action needs to be taken to correct the problem in order to maintain the efficiency, effectiveness,...Read More »

Predicting Engine Oil Behavior Under Extreme Pressure

The Industrial Fluid Properties Simulation Challenge is an open competition designed to push improvements in the field of molecular modeling and ensure simulations are relevant to real world industrial applications. The organizing committee of the challenge want to bridge the gap often found between theory and experimental applications....Read More »

Principles of Green Tribology

Peter Jost first used the term tribology in 1966 to describe the studies of science and technology that aim to understand how surfaces in relative motion to each other interact and the effects those interactions consequently have on the materials involved. Essentially, tribology started as the study...Read More »

How do phonons lead to frictional energy dissipation?

Friction is often associated with the generation of vibrations in the solids that are sliding over each other. Mathematically, these vibrations are described by the phonons in the two solids, the vibrational eigenmodes. Here, we are confronted with a conceptual difficulty, because the frictional interaction between the...Read More »

Tribology on the Small Scale: A Modern Textbook on Friction, Lubrication, and Wear

In recent decades, tribology field has seen a great interest in friction and wear processes occurring at the micro- and nanoscale. This interest has led to the development of a new branch of tribology focusing on the small scale phenomena – nanotribology. With the development of this field,...Read More »

Origins of Friction

A one million dollar question for a tribologist is as follows: where does the friction come from? Despite the undeniable progress in tribology in recent years, this question remains there. But there is a light at the end of the tunnel.

A research team of...Read More »

What is the difference between reciprocated and non-reciprocated sliding?

Sliding mode is an often overlooked aspect of tribological testing; in some applications surfaces are reciprocated with respect to each other, while in other applications the slider only contacts fresh counter surface. For example, in internal combustion engines the piston ring reciprocates against the cylinder wall, while our...Read More »

Friction and Wear: From Elementary Mechanisms to Macroscopic Behavior

In the last 25 years, the global trend to miniaturization has raised interest in frictional processes on the micro and nano scale and facilitated appearance of nanotribology as a new branch of research. Soon it became clear that looking at tribological processes at micro- and...Read More »

Green Tribology

Tribology is Integral to Global Energy Consumption, Costs and Emissions

Three principle industries in today’s society are transportation, power generation, and manufacturing. All three industries involve machines of all types, with moving parts subject to friction and wear, and therefore rely on tribology to help...Read More »

Creating a Robo-Dog Army: Tribological Aspects

Recently Boston Dynamics’ released a video of a robo-dog army pulling a truck down the road. The future is here. For now it looks like the good old Terminator I movie. But I guess...Read More »

Tribology of Earthquakes

Earthquakes are the sudden shaking of the ground caused by seismic waves passing through Earth’s rocks. These seismic waves occur when energy stored in the Earth’s crust is released suddenly, typically when large masses of rock pushing against each other suddenly break and slip. Typically, these occur along...Read More »

Should the contact area really increase due to sliding, and why this is never observed?


A paper by Menga, Carbone & Dini (MCD) recently published in prestigeous journal, suggests that in the contact with adhesion, the effect of tangential forces, and in particular of shear stresses assumed constant at the interface and equal to a material constant, an increase of contact...Read More »

Tribology and the Human Evolution

Tribology, not a common household word, is the science of wear, friction, and lubrication, studying how interacting surfaces behave in relative motion. Tribology does not work in isolation but affects a multitude of other fields including, but not limited to, mechanical engineering, manufacturing, chemical engineering,...Read More »

NASCAR Pile Up and Importance of Friction

A real life examples to help explain the importance of tribology are priceless. Car races can provide an exciting example. A pile...Read More »

Friction in Only One Direction

Nature has amazed us since the beginning of time. It provides the foundation for all of our best ideas. The animal world provides the inspiration behind one of the new inventions in the world of tribology – namely microstructured material designed with spatial variation to create one...Read More »

Fracture Physics and Crack Propagation

Fracture physics, a field of study in materials science, works on understanding how and why things break by quantifying and analyzing fracture surface topography. Scientists can reconstruct the history of a crack and determine the conditions that led to the initial formation of said crack. Preventing fractures is...Read More »

Leonardo da Vinci as a Tribologist

Tribology is the science dealing with interactive surfaces in relative motion and includes the study of friction, wear, and lubrication and how these properties affect design. The term tribology was coined in 1966 by Peter Jost, the man considered the founder of tribology. Leonardo da Vinci...Read More »

Tribology and Electric Vehicles

Electric Vehicles Through the Years

Electric vehicles, while often considered a new phenomenon, have existed since the 1800s. At that point in time, electric vehicles outnumbered gasoline powered vehicles for many reasons. Electric vehicles did not have the same vibration, noise, and smell of gasoline-powered cars....Read More »

Tracking a Sudden Fail of Microelectormechanical Systems

What time does it take before the minute parts of microscopic equipment become unusable as a result of deterioration? What warning signals do you need to watch out for that will show that the components will soon fail to function as required? In a bid to provide swift...Read More »

Phase-Switching Liquids Frost 300 Times Longer Compared to Known Anti-Icing Coatings

Ice and frost formation on surfaces afflicts various energy and transportation industries worldwide, causing economic losses in billions of dollars annually. Most techniques to prevent frost and ice formation on surfaces rely heavily on heating or liquid chemicals that need to be reapplied over and over again because...Read More »

Tribometer managing autumn leaf problem on railways worldwide

Since the 1800s, railway organizations have been struggling with low adhesion on the rail, especially during the Autumn season also known as the “slippery track season”. In Autumn, leaves fall on the rails and when train wheels crush the leaves, they become a layer of oil...Read More »

How can tribology help extend critical machinery service life?

Tribology is the science of interacting surfaces in relative motion. Basically, it studies friction, wear and lubrication – three phenomena linked to surface degradation and, thus, to machine reliability and performance. When machines wear out, they perform worse, are less productive and, finally, begin...Read More »

Friction has memory

Experiments show that the friction between two surfaces depends on their history of contact and that this “memory” is reminiscent of the behavior of glasses.

Contrary to what you may have learned in high school, friction between two surfaces is not constant. For a wide range...Read More »

Detect stress and fracture using color changing elastomers - mechanochromic sensors

Biological materials have complex mechanical properties that are difficult to reproduce using synthetic materials. An international team of researchers, including Dr. Andrey Dobrynin, a professor in The University of Akron’s College of Polymer Science and Polymer Engineering, has produced a biocompatible synthetic material that behaves like biological tissue...Read More »

Triboelectric nanogenerator to harvest energy from rain droplets

Despite the numerous advances in solar cells, one thing remains constant: cloudy, rainy conditions put a damper on the amount of electricity created. Now researchers reporting in the journal ACS Nano have developed hybrid solar cells that can generate power from raindrops.

In areas where it frequently...Read More »

Guidance Notes on Friction

In dry sliding between a given pair of materials under steady conditions, the coefficient of friction may be almost constant. This is the basis for two EMPIRICAL Laws of Sliding Friction, which are often known as Amontons’ Laws and date from 1699. They are in fact not...Read More »

Contact Mechanics Book

The Handbook on Contact Mechanics (Handbuch der Kontaktmechanik) co-authored by Honorary Professor of Tomsk Polytechnic University, head of the Department of System Dynamics and Friction Physics at Technical University Berlin, Valentin Popov, a TPU alumnus Emanuel Willert, and Assistant Professor of the Department of System Dynamics and...Read More »

Sharp knives - high friction

Trying to slice a tomato into thin slices with a dull knife can get a little scary. The harder the knife must be pressed downward before the skin is broken is directly related to the acceleration the knife experiences as it passes through the rest of the tomato...Read More »

On the history of elastohydrodynamics

Here we present an abstract to a paper devoted to the history of eastohydrodynamic theory and his founder – Alexander Mohrenstein-Ertel. This paper discusses in detailes the peculiar biography of the scientist and the early years of the theory development.

On the history of elastohydrodynamics: The dramatic destiny of Alexander...Read More »

White etching cracks

Today, bearing failure due to rolling contact fatigue is generally a rare occurrence, and the final achieved service life of rolling bearings is usually well in excess of the calculated rating life. There are instances, however, where...Read More »

Note on the history of contact mechanics and friction

No future without history! A great article on the history of great discoveries in the field of contact mechanics and friction was recently published by Elena Popova and Valentin L. Popov. Here we present the abstract of the article.


Great discoveries are often perceived by subsequent generations as sudden...Read More »

Minimum Quantity Lubrication Reduces Total Costs of Operation

SKF has employed Minimum Quantity Lubrication (MQL) for its own manufacturing processes and has also developed a comprehensive portfolio of MQL solutions through its LubriLean range. While SKF has recorded significant benefits from its introduction of MQL, including dramatic...Read More »

Study into the Rheology of Cats wins big at 2017 Ig Nobel Prize

From the brain’s responses to cheese aversion to the fluid dynamics of cats, WIRED picks its favourite Ig Nobel Prize winners for 2017

The winners of the 2017 Ig Nobel Prize, the science awards given to “achievements that first make people laugh then make them think” have...Read More »

The ‘Origami Robot’ that can be ingested

Ever swallowed a button-battery? And wondered how to get it out? Have no fear, the origami robot is here!

That’s right, the Massachusetts Institute of Technology (MIT) has come up with a pill-sized origami robot, which will help motor the unwanted plastic and other non-dissoluble...Read More »

World’s most powerful large-size bearing test centre in operation

SKF has a broad portfolio of extremely powerful software for the calculation and simulation of all types of rolling bearings. Among these are highly complex systems, which can investigate bearing behaviour in a virtual environment: With the...Read More »

Keeping the Wind in Your Sails

Just like any mechanical device, a wind energy system needs timely, appropriate lubrication in order to function reliably and predictably. Wind turbines routinely withstand extremely demanding conditions: vibration, high mechanical loads, contamination and moisture are all potential threats to operational efficiency, especially in critical rotating components such as bearings...Read More »

Friction: The Key to Rock Climbing

This article explains the vital role Friction has to play in Rock Climbing. Thanks to Richard Jones and Glen Harding for their input.

Friction is the magic ingredient in bouldering and rock climbing. It’s what makes the best moves and sequences subtle and surprising. Friction is a variable, some days it’s...Read More »

Modern Applications of Tribology

While Leonardo da Vinci commented on the effects of friction in the 1400s, it wasn’t until the mid-1960s that tribology was coined by Dr. H. Peter Jost and accepted as the term for the study and application of the principles of friction, lubrication, and wear.

In the early 1960s, there was...Read More »

The correct lubricant: a practical guide to choose lubricating oil

‘The correct lubricant’ covers basic practical information about lubricants in automotive and industrial areas. It is written for users of lubricants, giving only what is essential to know and useful for them. It could also be used by professionals in the field who must explain various aspects of...Read More »

Harvesting friction energy in self-sustaining water motion sensors

A recent study, affiliated with UNIST has engineered a self-sustaining sensor platform to continuously monitor the surrounding environment without having an external power source.

This research has been led by the team of Professor Jaehyouk Choi of Electrical and Computer Engineering at UNIST in collaboration with Professor...Read More »

Fight friction with plasma

For road vehicles, wind resistance increases fuel consumption. But one way to fight wind is with wind. Researchers in Sweden are experimenting with reducing drag on trucks with electric wind devices that mimic the way vortex generators increase lift on airplane wings.

You might have noticed them...Read More »

No Friction - Bad Earthquake

It is a common trope in disaster movies: an earthquake strikes, causing the ground to rip open and swallow people and cars whole. The gaping earth might make for cinematic drama, but earthquake scientists have long held that it does not happen.

Except, it can, according to new experimental research from...Read More »

Impact of water on Grease film thickness in rolling point contacts

In a rolling bearing, the load transmission is often accompanied by high contact stresses which may eventually lead to wear and/or fatigue. In order to ensure separation of moving parts leading to a long life, bearings are usually grease or oil lubricated. The separation of the moving parts in a...Read More »

After the Mystery of Rotary Lip Seals

Lip seals compete with mechanical face seals in sealing oil or grease in rotary shaft applications. Under certain running conditions both kinds of seals can be used however, the latter ones are generally used for applications where a significant pressure difference needs to be preserved. Rotary lip seals are preferred...Read More »

Friction is a possible reason for SpaceX Falcon 9 explosion

September 1 of 2016 at Cape Canaveral SpaceX lost is Falcon 9 rocket on a launch pad due to dramatic explosion. During a routine preflight fueling test, the  rocket and the $200 million Israeli Earth communication satellite Amos-6 were lost. No one was injured.

A...Read More »

What contributes to thicker grease films ?

A rolling bearing preferably runs under EHL conditions. The film thickness between the rolling elements and the rings is determined by the lubricant properties, operating conditions and bearing design. During the initial phase of operation, macroscopic flow (churning) of the grease takes place. It is usually during this churning phase...Read More »

Argonne Embraces Concept of "in operando" Formation of Carbon-based Tribofilms

Earlier this month, tribologists and physicists at the U.S. Department of Energy (DOE) Argonne National Laboratory published news of their (self-described) “self-healing diamond-like carbon coating [that] could revolutionize lubrication” in the journal Nature.  The researchers claim...Read More »

Contact Area vs. Load: Simple Scaling Laws

“God made the bulk; surfaces were invented by the devil”, a Nobel prize winning physicist Wolfgang Ernst Pauli said. In tribology, as in many other sciences, surface features (asperities, roughness) play an important role. In many cases, the surface roughness dramatically alters the friction, contact area,...Read More »

Small Particles - Big Problems

Tiny particles are all over around us and sometimes they may create problems. This is especially of concern with metal particles formed due to wear in man-made engineering devices. Particles formed in car disk brakes may harm lung cells, metal particulate limits the service life of artificial hip...Read More »

Determining Fatigue Wear Using Wear Particle Analysis Tools

...Read More »

Nordtrib 2016: conference summary and outlook on the field of tribology 50 years after the Jost report

Nordtrib 2016 came to a close last Friday and I returned home inspired and energized for the next stint in my PhD research. This post is an overview of the conference and summarises the outlook on the field for the years to come based on the round table discussions and...Read More »

Who is The First? Leonardo da Vinci!

Leonardo di ser Piero da Vinci, the famous Italian engineer, architect, painter, musician, mathematician can also be considered as The First Tribologist! Although the term itself was invented approximately 450 years after Leonardo da Vinci (1452-1519), he was the first one to perform the systematic study on friction,...Read More »

Bio-lubricants and Environmentally Acceptable Lubricants (EAL)

The increasing awareness on environmental pollution caused by many chemicals, including lubricants, promotes the use of environmentally friendly products. There is a clear trend towards a more responsible use of lubricants and several legislations already limit the use of certain oils in some applications. Bio-lubricants are present in construction, mining...Read More »

In Situ Nanopolishing (ISN): A New Lubrication Paradigm Aimed at Permanent Surface Perfection

All conventional lubricants borne of classic hydrodynamic theory are designed to provide lubricity. Inherent in the desire to provide lubricity to mechanical systems is the desire to protect the interacting metal surfaces from wear. Much effort in tribology...Read More »

Surface Replication Compounds

The first challenge when measuring a surface topography via optical techniques is getting the sample to the lab. Although optical surface roughness measurement does not damage the component per se (NDT), the fact of fitting it into a microscope generally requires the destruction of the original component. The surface replication...Read More »

Wear in nanoscale: optimum AFM tip roughness

Wear is a gradual removal of the material of the bodies during their interaction. The process appears in many mechanical systems, ranging from large scales, as in wind mills, to nanoscales, as in the AFM tip – substrate contact. The macroscale wear is a relatively well developed field of tribology,...Read More »

"Car 2020" and Tribology Research

Friction has been a challenge for the mankind throughout the whole history since it resists the motion. It resists the transportation of goods. And transportation shares 20% of the global energy consumption and approximately 18% of the greenhouse gas emissions. Out of this share, road transportation builds up to 72%...Read More »

Ice Lubrication and the Forbidden City

Forbidden City is a historical symbol of China, located in the center of Beijing and was constructed between 1406 and 1420 . It served as an imperial palace for almost 500 years and consists of 980 buildings on 180 acres area. Large number of massive buildings required mining and transportation...Read More »

So, what is it, superlubricity?

From the first friction quantitative experiments by Leonardo da Vinci (1452-1519) and most notably from our everyday life experience, it is known that there is an inevitable force opposing to the initiation of motion of one body on the surface of another. This force has to be exceeded, in order...Read More »

Modeling rough adhesive surfaces

Imagine a new type of tyres whose structure has been designed to have greater adhesion on the road. Quite a timely discussion during the long winter nights. French physicists have now developed a model to study the importance of adhesion in establishing contact between two patterned, yet elastic, surfaces. Nature...Read More »