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The onset of wear-and ways to reduce it-emerge from an exciting modeling and experimental collaboration.
UNCONSTRAINED PLASTIC FLOW (UPF) OF METAL SURFACES IN A SLIDING CONTACT with hard asperities is a common tribological occurrence, whether it be deliberate (e.g., in machining) or accidental (wear processes on metal surfaces). In the latter case, UPF-and thus wear-can be influenced by preconditioning the surfaces, using processes such as lapping, honing or running in. These techniques are known to modify the crystalline structure, topography and even to some extent the chemical composition in the surface-near region. Precisely how these influence wear has not, up to now, been very clear.
Some recent observations have suggested that UPF of metal surfaces is not a laminar process, as had been previously assumed, but can produce vortex-like fold structures, which are a precursor to wear-particle formation. A team led by Peter Gumbsch, Michael Moseler and Martin Dienwiebel at the Fraunhofer Institute for Mechanics of Materials in Freiburg, Germany, in collaboration with industrial colleagues at...