The traditional laws and models of friction, such as Leonardo da Vinci and Amontons’ Laws of friction, and the Stribeck Curve for lubrication, were expounded many years ago (da Vinci in the late 15c). These pioneers of tribology introduced terminologies, such as the Coefficient of Friction (COF), mixed lubrication, and concepts or “laws” (like the velocity independence of the COF, and the “contact area” or film thickness) that break down or that do not apply or that cannot be measured in many practical tribological and especially lubrication situations, and where the length, load/pressure, time and rate (velocity) scales can vary by many orders of magnitude – for example, nm-µm contact diameters for particle interactions compared to &gt;10 km in geological fault lines – a difference of 13 orders of magnitude in length (and much more in area). Likewise, for slow ‘creeping’ sliding at nm/s – mm/s compared to &gt;10 m/s in machines and engines. Additionally, stiction and stick-slip sliding and their implications for wear, sound generation, sensory perception and biolubrication, do not fit naturally into any of the original laws or concepts, yet these often are <i>the</i> major tribological parameter of many systems, for example, in generation surface damage (wear). The talk will review recent and not so recent experimental and theoretical (computational) examples of the “New Tribology”, illustrating how many different processes, such as those mentioned above, that cover large ranges of length and time scales, can be better understood within more general and unified theories and/or concepts.

Friction and lubrication from the nano (molecular) through the micro (µm-mm) to the macro (geological) scales, and over large time and velocity scales

253rd National Meeting (2017)

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