Tribology: “The Most Important Subject No One Has Heard Of”
Perhaps, more accurately, this piece should be called “Tribology: The Most Important Multidisciplinary Conglomeration of Related Sciences No One Has Heard Of” though that doesn’t have quite the same ring to it. The title quote is from Professor John Tichy of RPI, New York, and seems to sum up the weary attitude of many tribologists.
Tribology is a subject name that will earn you blank stares even from fellow scientists, let alone a stranger at a party – or your grandmother. I think most people would be surprised to learn just how prevalent tribology is in our world, and it’s fair to say that those of us involved in the subject end up with a much deeper (if nerdier) appreciation for how the world works.
When I respond to the dreaded “so what do you do?” question, reactions to “tribology” have included polite smiles, assumptions that I carry out anthropological studies of African tribes and, in one case, the enthusiastic exclamation “Do you engineer Tribbles?” (which was a little awkward, as I don’t watch Star Trek and had to Google ‘Tribbles’). It is one of those subjects that is seemingly so specialist it requires a long explanation and sometimes leaves the listener no better off than before.
Yet it shouldn’t be so. Tribology, when you break it down into its component parts of friction, wear and lubrication, is arguably the most influential science encountered in daily life. It is usually classified as part of mechanical engineering, however it is a wonderfully multi-disciplinary subject . While my own background is mechanical, my fellow PhD students have backgrounds in physics, chemistry, materials and medical science, to name but a few. It is the combination of so many aspects of science that makes it a fascinating topic on any level.
So what is tribology, really? The official definition is “the science of interacting surfaces in relative motion”. This might shine a light for those already schooled in technical subjects but it didn’t help much when I tried to explain it to my mother.
What it essentially boils down to is things touching and rubbing together. The term comes from a Greek word, tribos (“rubbing”). Tribology as we know it today was initiated in the 1960s, when a committee chaired by Dr Peter Jost proposed the study of this new branch of science to bring together the previously separate fields of friction, wear and lubrication. The study perceived a lack of knowledge in this area – not just in research areas but in industry, where good tribological practice could potentially save millions of pounds .
Tribology affects everything we do, which is what makes it such a broad topic. Any industry you care to name will use tribology to one extent or the other; from automotive to aerospace, from human joint replacements to toothbrushes. Some benefits are more obvious than others – for instance, tribology is responsible for the development of multigrade oils used in car engines. Before multigrades, you would change the oil between summer and winter, as ambient temperature affected the viscosity of the oil. As the temperature increased (i.e. over the summer months), oil molecules spread out and wouldn’t interact with one another. Long-chain polymers can be added to the oil, which tangle up amongst the molecules and stop them moving apart. This allows the oil to behave in the same way regardless of the temperature and results in lubricants that can be used all year round – which makes life a lot easier for motorists!
Other benefits are less intuitive. Tribology is highly important in sports of all kinds, often for completely contrasting reasons. For instance, climbing shoes need a high friction coefficient with the surfaces they encounter – the last thing climbers want is their feet slipping when they’re hanging off a rock face or building. Spiderman himself would be no more than a strange man in a onesie if not for high friction. On the other hand, any snowsport requires the lowest friction possible to allow skiers, snowboarders and skaters to glide over surfaces more quickly than anybody else.
A recent application that personally fascinates me is a connection between two seemingly disparate areas of tribology – linking winter sports with railways. How does this work? Well, many people can attest to having their trains delayed or cancelled because of “leaves on the line”. The reason for this, in short: when leaves lie on a train track, the extremely high pressures exerted by the train wheels cause an extremely low friction coefficient between the wheels and the rail, which causes all kinds of problems for the trains. The knowledge of this effect can be applied to skis: by copying the structure of leaves that cause low friction, a superhydrophobic layer can be created for the base of a ski . Hydrophobicity is a measure of how much a material repels water and it’s been established that skis slide on a thin water film created between the ski and the snow. The less contact with the water film, the less friction will hinder the movement of the ski. The increased hydrophobicity not only improves performance but also presents other advantages, such as reduced maintenance (as a superhydrophobic ski base may not require waxing). This example demonstrates so clearly the wide range of applications and benefits that comes from tribological research.
So what do I say when people ask me, in a slightly puzzled voice, why I study a subject that is so apparently obscure? Honestly – because it’s fun. Because I love how a single subject can pull together so many areas of science. A tribologist can be useful in any industry, in any research, in any job. I’ll have to put up with plenty more people giving me blank stares when I tell them what I do, but I don’t really mind. I’m happy to help make sure that one day it won’t be such an obscure topic after all.
by Heather McLaren, 1st year PhD Tribology
 Interview with H. Peter Jost, Tribology, January 1968
 Lubrication (Tribology) – Education and Research. A report on the present position and industry’s needs, 9th March 1966
 N. A. Nordin, P. Styring, Superhydrphobic Ski Bases for Reduced Water Adhesion, Procedia Engineering 72 (2014) 605-610