title: Molecular Dynamic Simulation of Collision-Induced Third-Body Formation in Hydrogen-Free Diamond-Like Carbon Asperities.
abstract: The collision of two cylindrical hydrogen-free diamond-like carbon (DLC) asperities with approximately 60 % sp3hybridization has been studied using classical molecular dynamics. The severity of the collision can be controlled by the impact parameterbthat measures the width of the projected overlap of the two cylinders. For a cylinder radius ofR= 23 nm, three collisions withb= 0.5 nm,b= 1 nm andb= 2.0 nm are compared. While for the two smallba single shear band between the collision partners and a strongly localized sp2/sp1hybridised third-body zone between the asperities is observed, theb= 2 nm collision is accompanied by pronounced plastic deformation in both asperities that destabilize the metastable sp3-rich phase leading to a drastic increase in the amount of rehybridized tribomaterial. In addition, pronounced roughening of the cylinder surfaces, asymmetric material transfer and the generation of wear debris are found in this case. For theb= 0.5 and 1 nm collision, the evolution of third-body volume can be quantitatively described by a simple geometric overlap model that assumes a sliding-induced phase transformation localized between both asperities. Forb= 2 nm, this model underestimates the third-body volume by more than 150 % indicating that plasticity has to be taken into account in simple geometric models of severe DLC/DLC asperity collisions.
authors.affiliation: Fraunhofer IWM, MicroTribology Center, Wöhlerstraße 11, 79108 Freiburg, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: von Lautz
authors.affiliation: Fraunhofer IWM, MicroTribology Center, Wöhlerstraße 11, 79108 Freiburg, Germany ; Institute for Applied Materials, Karlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Pastewka
authors.affiliation: Fraunhofer IWM, MicroTribology Center, Wöhlerstraße 11, 79108 Freiburg, Germany ; Institute for Applied Materials, Karlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Gumbsch
authors.affiliation: Fraunhofer IWM, MicroTribology Center, Wöhlerstraße 11, 79108 Freiburg, Germany ; Institute of Physics, University of Freiburg, Herrmann-Herder-Str. 3, 79104 Freiburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Moseler
keywords: Asperity collision; Diamond-like carbon; Geometric overlap model; Rehybridization; Shear bands; Third body; Tribo-induced phase transformation