The mechanisms of Folding and Wear particle generation in metallic tribosystems

M. Dienwiebel,1,2N. Beckmann,1,2 P. A. Romero,1 D. Linsler,1,2 U. Stolz,3 M. Moseler,1,4, and P. Gumbsch1,2

1Fraunhofer Institute for Mechanics of Materials IWM, MicroTribology Center µTC,

Wöhlerstrasse 11, 79108 Freiburg, Germany

2Karlsruhe Institute of Technology, Institute for Applied Materials IAM, Strasse am Forum 5, 76131 Karlsruhe, Germany

3Robert Bosch GmbH, Robert-Bosch-Campus 1, 71272 Renningen, Germany

4Faculty of Physics, University of Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany


Abstract

The formation of third body and wear debris of low wear metallic tribosystems can be attributed to severe plastic flow at the interface. Wear particles often consist of very thin nanocrystalline sheets of material and several mechanism have been previously discussed that might explain their morphology. In our recent study [1] we investigated the mechanism of surface folding  [2] of copper as a precursor to wear particle generation by a combination of atomic force microscopy wear experiments and massive molecular dynamics simulations.

 In agreement with experimental findings, the simulation shows bulges in front of a model asperity develop into vortex-like fold patterns that mark the disruption of laminar flow. We identify dislocation-mediated plastic flow in grains with suitably oriented slip systems as the basic mechanism of bulging and fold formation. The observed folding can be explained by the inhomogeneity of plasticity on polycrystalline surfaces which favors bulge formation on grains with suitably oriented slip system.  


References

[1]        N. Beckmann, P. a. Romero, D. Linsler, M. Dienwiebel, U. Stolz, M. Moseler, and P. Gumbsch, Phys. Rev. Appl. 2, 64004 (2014).
[2]        N. K. Sundaram, Y. Guo, and S. Chandrasekar, Phys. Rev. Lett. 109, 106001 (2012).