VTT: New friction technology translates into major energy and cost savings
Friction gives rise to both costs and emissions. It has been estimated that as much 30 per cent of production in the industrialised countries goes to replacing worn-out parts. More than one third of the world’s energy is used to overcome friction. Energy savings equalling the annual production of one nuclear power plant could be reached in Finland alone by utilising the latest friction technology.
The costs caused by friction and wear are very high worldwide. According to surveys carried out in different countries, the economic losses resulting from friction and wear are 1-2 per cent of the GDP. In the United States, for example, reducing friction and wear in engines and transmissions would save 120 billion dollars per year.
Friction and the resulting wear and breakdown of machine parts can stop entire production plants for a long time. The costs arising from the shutdown can be very high. It is estimated that the costs arising from the shutdown of a coal-fired power plant are EUR 800 000 per week, of a paper and pulp mill EUR 1.5 million, and of a nuclear power plant EUR 2.2 million.
Friction and wear show in energy consumption, so in this sense, too, they are major sources of emissions affecting climate change. It is possible to reduce carbon dioxide emissions from traffic and industry by 2-10 per cent by means of new technological friction solutions. Mere vehicle rolling resistance makes up 20 per cent of fuel consumption.
There are technological solutions to overcome the problems caused by friction and wear, by means of which energy can be saved and material durability improved. The science and technology investigating problems and solutions of this kind is known as tribology, which investigates interacting surfaces in motion.
VTT has been developing technological and material solutions to reduce friction. It makes use of the latest modelling technology for preventing surface cracking and breaking and for determining optimum mechanical surface properties, coating thickness and adhesion.
Operation of machines relies on an extremely thin film
The friction and wear of machines is controlled by means of films or coatings. Oil is one of the substances widely used to form a lubricating film between two surfaces in motion. The operation of machines often relies on extremely fine films, which prevent materials from rubbing against each other, thus reducing friction and wear.
The most durable and friction-free coatings are an almost friction-free carbon coating, a diamond-like coating, and a molybdenum sulphide coating. A common friction-preventing coating is Teflon®, which is used in saucepans and frying pans.
Many problems causing friction and wear can be solved quite easily. The rolling resistance of vehicle tires can be reduced using harder tires, higher tire pressure and softer suspension, and by driving slower. Engine friction can be reduced by means of new oil additives and low-friction coatings, such as a diamond-like coating. The lifetime of consumer products can be increased by means of material solutions and wear-resistant coatings. The friction generated when seawater encounters a ship’s hull can be reduced through coating. The friction in factory conveyors, mineral processing, mixers, blowers, pumps, and regulating valves can be reduced through lubrication, coating, and the selection of materials.
Computer models help in finding a solution
Friction and wear are not just material properties that could be addressed by selecting a harder material, for example. They arise in the contact between materials, which in turn is affected by several factors, such as contact, load, speed, surface and base material hardness, elasticity, toughness, chemical properties and lubrication, and the prevailing environmental factors, including temperature, humidity, impurities, and radiation.
Exact computer models of the point of contact and the simulation of the resulting forces, tension, deformation, and elongation help identify the most important variables affecting friction and wear and calculate their interaction.
With a working computer model, it is possible to calculate the impact of different variables on friction and wear fast, reliably and accurately, and thus find a suitable solution. The conformity of computer models with reality is ensured by comparing them with experimental laboratory measurements.
VTT has an internationally world class friction laboratory, where friction and wear is measured under carefully controlled laboratory conditions in both in dry and lubricated modes.
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