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How can shear loading rate affect the soft adhesive contact area?

Today, my youngest daughter dropped her spoon again on the floor. She didn’t do it on purpose. But I still had to get it back again, give it a quick wash again and give it back again… What’s wrong? It’s not that hard to hold it well!

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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 »


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How does roughness impact your EHD contact?

 

A bit of context

Let’s say you want to design a new car but that you are a new car manufacturer. You can’t really step back and look at your previous experiences, so everything you design in this car has to be carefully calculated… and you will still make mistakes!...Read More »


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Which is the best texture?

Every so often, a natural texture is discovered and presented as a great texture for tribology purposes! Shark skin, leaf surface, or even snake skin are the most renowned examples. And it is true that the textures found on these organisms are amazing. But these textures...Read More »


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Scope of Artificial Intelligence and Machine Learning in Tribology

Introduction to AI and ML

Right from mobile phone apps which recommend our favorite music to the most sophisticated autonomous vehicles, every device in today’s times is embedded with artificial intelligence and machine learning. Taking this as an inspiration every field of science is looking for different...Read More »


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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 »


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Towards a model of hydration-lubricated contact

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

Have you ever tried to cross a small river by jumping from one emerging stone to another? I always try when I go on a walk! But...Read More »


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Origins of Sliding Friction

Origin of sliding friction: role of lattice trapping

The article was co-authored by Dr. Avinash Tiwari, Postdoctoral Researcher at Forschungszentrum Jülich.
The article was co-authored by Dr. Jianjun Wang, a visiting scholar...Read More »
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Atomic scale deformation responsible for surface roughness

The article was written by Dr. Aydar Akchurin

Most of the natural or engineered surfaces are not perfect, meaning they are rough. The surface roughness was found across many scales: from atomic to tectonic. The earth looks...Read More »


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Physicists are one step closer to understand lubrication at nanoscale

The article was written by Dr. Aydar Akchurin

The famous picture of transportation of an Egyptian statue to the grave of Tehuti-Hetep, El-Bersheh indicates that the concept of lubrication was already known to ancient Egyptians. The...Read More »


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Minimal Quantity Lubrication: Drop on Demand Printing Technique

The article was written by Dr. Aydar Akchurin

Recent research (https://doi.org/10.1007/s40544-017-0183-5) 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 »


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Early Mechanical Behaviors and Origins of Earthquakes

Hadrien Rattez, a research scientist in civil and environmental engineering at Duke University and Manolis Veveakis, an assistant professor of civil and environmental engineering at Duke University, have joined forces to create a model, which is capable of predicting early mechanical behaviors as well as the origins of...Read More »


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Models Predicting When and How Roads Will Deteriorate

Heriberto Perez, a researcher at the UPV/EHU’s Faculty of Engineering-Bilbao, has developed behavior models able to predict the future deterioration of roads. The models focus on two different aspects, the international roughness index (IRI) and the coefficient of transverse friction. The purpose of the models is to...Read More »


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Mystery of Friction and Static Electricity

Every child has experienced the magic of static electricity. Eyes light up as he or she performs magic by rubbing a balloon against his or her hair and the balloon then sticks to the wall.

Static electricity is, in actuality, an imbalance of electric charges with...Read More »


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A two-body abrasive wear model as a contact-induced fracture process

A recent work by the researchers from Leibniz University Hannover presents a 3-D framework for simulation of contact-driven-fracture processes (like abrasive wear) in filled elastomers. Modeling of material removal processes, like wear, to this day remains an empirical art. Since the prolific work of J. F. Archard...Read More »


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Predicting Wear of Marine Infrastructure due to Ice Melting

Rubble ice is a jumble of ice fragments or small pieces of ice, which cover an expansive area with no particular pattern or order. Areas in the Arctic and Antarctica have large expanses of rubble ice where the strong winds and ocean waves break up newly forming ice...Read More »


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Sediments Act As Lubricants for Plate Tectonics

Plate tectonics explains the features and movement of the Earth’s surface both in the present and in the past. It is the theory that the outer shell of Earth is divided into many plates (including a few major plates as well as dozens of minor plates) that...Read More »


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Modeling Ice Friction

Glaciers and Ice Friction

Glaciers are comprised of snow accumulated over many years and compressed into large ice masses. Formed when snow remains in a location long enough to form ice, glaciers are unique in that they have the ability to move, flowing like extremely slow rivers...Read More »


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Analyzing the evolution of adhesive wear

Adhesive Wear Analyzed

The effects of surface wear reaches across many industries including production, manufacturing, engineering, transportation, roads, and machinery, to name only a few. Given its wide reaching tentacles, it can be surprising to realize that surface wear is still not completely understood.

Surface...Read More »


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Sticky or Not Sticky?

Numerical analysis of adhesion of rough surfaces shows that there exist one unique parameter determining whether the surface is sticky or not.

It is well known that neutral bodies attract each other by van der Waals forces. However, adhesive forces in macroscopic systems often are negligible. Kendall...Read More »


Simulations explain why the ice is so slippery

Everybody knows that sliding on ice or snow, is much easier than sliding on most other surfaces. But why is the ice surface slippery? This question has engaged scientists for more than a century and continues to be subject of debate. Researchers from AMOLF, the University of Amsterdam...Read More »


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Employing machine learning to create wear and corrosion resistant metallic glass

If you combine two or three metals together, you will get an alloy that usually looks and acts like a metal, with its atoms arranged in rigid geometric patterns.

But once in a while, under just the right conditions, you get something entirely new: a futuristic alloy called metallic...Read More »


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Contact Area Calculation Tutorial: Boundary Element Based Model vs. Asperity Based Model

In contact mechanics and tribology it is frequently needed to calculate the contact area between rough surfaces to estimate possible slip, friction, electric conductivity, etc. In this tutorial, it will be shown how to perform this calculation using a freely available software – Tribology Simulator....Read More »


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Knowing the strength of adhesion

How can flies walk on the window glass upside down? How can geckos climb walls and trees? It looks like a simple question, but it is hard to answer. The secret is that flies and geckos, and many other living species can control the ability to stick to surfaces, ability to adhere. Adhesion has...Read More »


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A very simple estimate of adhesion with rough surfaces based on a bearing area model

Here we present an abstract to the paper addressing a simplified model for adhesion between hard rough solids.

Abstract

In the present note, we suggest a single-line equation estimate for adhesion between elastic (hard) rough solids with Gaussian multiple scales of roughness....Read More »


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Some open problems in adhesion (of rough surfaces)

By M.Ciavarella, A. Papangelo. Politecnico di BARI, Italy.

Adhesion for ‘‘soft’’ bodies shows instabilities like in the simple case of a single sinusoid even in the so called JKR regime (Johnson 1995) which leads to hysteretic behavior. Hence, for very soft and large bodies, and special types of...Read More »


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Simulating Physics

Nature is quantum mechanical, and UCSB/Google researchers are ready to study it with a nine-qubit array and the problem of many-body localization

When does a metal stop being metallic? When do atoms start breaking the rules of chemistry as we know them? To the naked eye, and...Read More »


measurement of droplet motion

Droplet friction is similar to solid friction

Researchers of the Max Planck Institute for Polymer Research have investigated friction of liquid droplets on surfaces. A larger force is needed to set in motion stationary droplets than to keep moving droplets in motion. This behavior is already known for solids on surfaces. For the case of...Read More »


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Contact Pressure For Rough Surfaces: A Tutorial

In this article, a calculation of contact pressure in a rough contact is discussed. The calculation is done using a Tribology Simulator software, which is available for download here (its free to use). The simulator uses a Boundary Element Method (BEM) with Fast Fourier Transform...Read More »


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Contact mechanics challenge results

The Contact-Mechanics Challenge completed

In late 2015 we posed the Contact-Mechanics Challenge. This has now been completed and the winner is—the field of tribology.

BECAUSE TRIBOLOGY IS THE STUDY OF contacting bodies in relative motion, a fundamental issue is to understand the nature of the interfacial contact as a function of load...Read More »


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Simulation reveals previously unknown friction mechanisms of diamond at the molecular level

Diamond coatings are commonly used today to protect tools and machine components that are subjected to high wear, and thus to extend their service life. It is known that rubbing two dry diamond surfaces together creates enormous friction due to the bonding of reactive carbon atoms on each...Read More »


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Zeroing in on ZDDP tribofilm growth

Models for the stress-activated growth of tribofilms from ZDDP were modified to include wear.

TWO RECENT CUTTING EDGE ARTICLES reported on work that showed the growth rates of tribofilms from ZDDP were accelerated by contact stress1 or interfacial shear2 under conditions in which the temperature rise caused by rubbing was negligible....Read More »


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Say “modeling” not “simulation”

Richard M. Stallman, founder and president of the Free Software Foundation and founding father of the GNU Project, has a long been repeating “say GNU, not Linux” although he has not had much success. In the same sense, from this corner of the world I will begin a similar battle. I...Read More »


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Adhesive wear model: particle by particle

10.07.17 – An EPFL study has deepened our understanding of the fine particles produced by adhesive wear. This breakthrough could lead to cost savings and environmental benefits.
Adhesive wear occurs when two surfaces – such as a brake pad and a wheel’s disc, or a car tire and the...Read More »
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Tribology at Work on the Strings

There’s something about the moan and wail of a good gut-bucket slide guitar riff that can grab you by the innards and not let go. Any tribologist worth his salt is likely to have another reaction: “A bit high on the tribometer, that.”

Blues, bluegrass, and Hawaiian slide guitar fans know...Read More »


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Elmer: An Open Source Finite Elements Software

There are nowadays some Open Source Finite Elements packages available online, just to cite some: CalculixSalome-Meca (with Code Aster)Z88 AuroraElmer, etc.

The gap between the paid software (AnsysComsolAbaqus, LS-DYNA,…) and the open source packages is still big, especially when it comes to the GUI and...Read More »


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Reducing wind turbine operating costs through a statistical approach

Summary

Taking a statistical approach to the condition monitoring of wind turbines is helping wind energy operators control their operation and maintenance costs. SKF is using its wealth of knowledge and considerable database about thousands of wind...Read More »


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Stress Assisted Tribofilm Growth: A New Model

Under extreme conditions the lubricant film fails to separate the rubbing surfaces and solid-to-solid contact occurs. To prevent excessive wear of the base materials anti-wear additives are used in these cases. The additives create a protective layer which is worn instead of the base materials and allows to control the...Read More »


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Mixed Lubrication: Wear Particles Size and Friction Evolution

Wear in tribological contacts results in generation of wear particles of various sizes and shapes and these particles impact the performance of the mechanical devices. These particles may create additional mechanical damage or act as catalysts and adversely affect the lubricating properties of lubricants. The size of the generated wear...Read More »


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Nonequilibrium molecular dynamics simulations of organic friction modifiers

The requirement for greater energy efficiency in engineering systems has led to a general reduction in lubricant viscosity, which means that an increasing number of engineering components operate under boundary lubrication conditions. As a result, lubricant additives that reduce friction and wear under boundary conditions are of increasing...Read More »


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Predicting the size of wear particles

A wear process results in the generation of particles, of various size, shape, color and chemical composition. The reported size of wear particles varies from mm scale, which is typically attributed to severe wear, to nm scale in the range of 5nm in mild wear. In general wear particles influence...Read More »


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Slip, No Slip and Cavitation

Engineering surfaces are heterogeneous and can be slippery or sticky locally depending on surface roughness and chemistry. The variation of surface properties affects the interaction between the wall and lubricant and determines friction. Slip can be used to control friction in lubricated devices.

In hydrodynamic theory, the slip is quantified by...Read More »


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Adhesive Wear Particles Generation: by Fracture or Atom-by-Atom?

The most famous equation to predict wear known probably to everyone working in the field of tribology  is Archard’s model (1953). The model assumes that wear occurs through the fracture of plastically deformed material and generation of wear debris. The fracture nature of the wear debris is backed up...Read More »


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Ab Initio Analysis of Carbon Film Lubricity

Carbon-based nanomaterials, coatings and films attracted a great attention due to proved possibility to achieve lowest friction and wear without environmental pollution. However, frequently, the state of the low friction is strictly related to the air humidity, which limits the areas of applicability of many carbon-based lubricants. To control and...Read More »


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Hysteresis in Friction of Graphene

Friction is a result of complex interaction of physical, chemical and mechanical forces at the sliding interface. Due to mentioned complexity, truly predictive models of friction are yet to be developed. As a result of the complexity, various phenomena rise, as for example friction hysteresis due to the change of...Read More »


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Molecular Dynamic Simulations and AFM Experiments at Overlapping Speeds

Atomic Force Microscopy (AFM) is a powerful and convenient experimental measurement device in the field of nano-scale tribology. It was successfully applied to explore superlubricity in a graphene-gold interface and  superlubricity due to repulsive van der Waals forces, to grow tribofilms and...Read More »


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Molecular Dynamic Simulations of Zinc Phosphate - Iron Oxide Reaction

In order to improve wear resistance of the surfaces operating in harsh conditions, along with base oils additives are frequently used.  ZDDP is one of the best additives in terms of antiwear performance, however, environmentally unfriendly. The search for a new, environmentally friendly and antiwear efficient substitute for ZDDP is...Read More »


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Mechano-chemical wear and tribofilm thickness simulation

When the conditions in the tribosystem are such that the lubricant is not capable of carrying any significant part of the applied load, most of the load is carried by the direct contact of the rubbing surfaces and a boundary lubrication regime is established. More and more mechanical systems operate...Read More »


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Inverse Friction Force - Load Dependence of Graphene

When the bodies slide against each other, the classic Amonton’s law states that the friction force is directly proportional to the applied normal load. This law holds true for various if not most of the engineering materials, like metals, ceramics etc. At the same time, the law is in agreement...Read More »


Anyone is up for challenge?

Society of tribology and lubrication engineers announced Contact Mechanics Challenge.   Dr. Martin Müser initiated a competition in calculation of a real contact area. He has already results of his own calculation and challenges other groups to join and compare the results. As an outcome, there will be a paper discussing...Read More »


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