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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


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 »


MD_Simulation_Tribofilm

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 »


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 »


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 »