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Wednesday, 19. August 2015 12:22 Age: 2 yrs

Applicability of Macroscopic Wear and Friction Laws on the Atomic Length Scale

Category: Scientific Highlights

Published in Physical Review Letters

Nanoscale wear follows big-world rules

At the level of atoms, the world often behaves quite differently than at the scale of everyday things. In this letter, using numerical simulation we found some evidence of the contrary: when rubbing two rough nanoscale objects against each other, the wear of the softer of the two surfaces progresses in much the same way as would be expected at a much larger macroscopic scale. This is mainly because in our model system, multiple tips of the two surfaces are in contact at the same time. Furthermore, our calculations showed that even when wear is involved, the resistance to the rubbing motion is proportional to the amount of contact between the two surfaces, which is difficult to measure experimentally. Our work constitutes an important step toward bridging the gap between the nano- and the macroscale, and it will help scientists with interpreting atomic force microscopy experiments correctly.

Abstract:

Using molecular dynamics, we simulate the abrasion process of an atomically rough Fe surface with multiple hard abrasive particles. By quantifying the nanoscopic wear depth in a time-resolved fashion, we show that Barwell’s macroscopic wear law can be applied at the atomic scale. We find that in this multiasperity contact system, the Bowden-Tabor term, which describes the friction force as a function of the real nanoscopic contact area, can predict the kinetic friction even when wear is involved. From this the Derjaguin-Amontons-Coulomb friction law can be recovered, since we observe a linear dependence of the contact area on the applied load in accordance with Greenwood-Williamson contact mechanics.

Figure:

(a) Initial system configuration with cubic abrasive particles. The abrasives are shown in gray, and the Fe substrate is colored according to the local height, where blue denotes low and red denotes high.

(b) Overview of the deformation zones to which an atom can be attributed according to its momentary advection velocity v, where v(max) is the sliding velocity of the abrasive particles.

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License.P09 Complex magnetic structures

Read the article in derstandard.at about this publication (german only)

Eder S.J., Feldbauer G., Bianchi D., Cihak-Bayr U., Betz G., Vernes A. (2015), Applicability of Macroscopic Wear and Friction Laws on the Atomic Length Scale, Physical Review Letters 115.  DOI:10.1103/PhysRevLett.115.025502, Open Access, report in derstandard.atP09



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