03.08.18 – Drawing on the fact that the snow in an avalanche can behave like both a solid and a fluid, a young researcher at EPFL and SLF has managed to simulate a snow slab avalanche with unrivaled precision.
An avalanche is an extremely...Read More »
Findings may help track movement of pesticides and biological contaminants.
As a single raindrop falls to the ground, it can splash back up in a crown-like sheet, spraying smaller droplets from its rim before sinking back to the surface — all in the blink of an eye.
Now researchers at MIT have...Read More »
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 »
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 »
Each year, the effects of corroding materials sap more than $1 trillion from the global economy. As certain alloys are exposed to extreme stress and temperatures, an oxide film begins to form, causing the alloys to break down even more quickly. What precisely makes these high-temperature, high-stress conditions...Read More »
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 »
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 »
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 »
Here we present an abstract to the paper addressing a simplified model for adhesion between hard rough solids.
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 »
Sandia developing specialized computer modeling and simulation to characterize injury
Sandia National Laboratories is developing specialized computer modeling and simulation methods to better understand how blasts on a battlefield could lead to traumatic brain injury and injuries to vital organs, like the heart and lungs.
Researchers at Sandia...Read More »
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 »
Simple equation predicts force needed to push objects through granular and pasty materials.
For those of you who take sandcastle building very seriously, listen up: MIT engineers now say you can trust a very simple equation to calculate the force required to push a shovel — and any other “intruder”— through...Read More »
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 at room temperatures, such...Read More »
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 »
Forty years ago, MIT emeritus professor of mechanical engineering Ernest Rabinowicz calculated that 6 percent of the annual U.S. gross domestic product was lost through mechanical wear. His assertion gained enough traction that it became known as the “Rabinowicz Law.”
“Even so, the mechanism by which mechanical wear happens is one...Read More »
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 »
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 surface with...Read More »
Got rope? Then try this experiment: Cross both ends, left over right, then bring the left end under and out, as if tying a pair of shoelaces. If you repeat this sequence, you get what’s called a “granny” knot. If, instead, you cross both ends again, this time right over...Read More »
“3-D physics engine” from the Computer Science and Artificial Intelligence Laboratory simulates the human brain to infer physical properties.
We humans take for granted our remarkable ability to predict things that happen around us. For example, consider Rube Goldberg machines: One of the reasons we enjoy them is because...Read More »
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 »
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 »
Adhesive wear occurs when two surfaces – such as a brake pad and a wheel’s disc, or a car tire and the...Read More »
The mechanical properties of sheet metal materials are directional: their deformation behavior and their strength differ significantly depending on the viewing direction, for example in the direction of rolling or transversely to it. Numerous complex load tests therefore have to be carried out in order to obtain the necessary material...Read More »
There are no mechanics on Mars, so the next best thing for NASA’s Curiosity rover is careful driving.
A new algorithm is helping the rover do just that. The software, referred to as traction control, adjusts the speed of Curiosity’s wheels depending on the rocks it’s climbing. After 18 months of...Read More »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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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