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Molecular dynamic simulation of collision-induced third-body formation in hydrogen-free diamond-like carbon asperities

: Lautz, J. von; Pastewka, L.; Gumbsch, P.; Moseler, M.

Fulltext urn:nbn:de:0011-n-4233646 (4.0 MByte PDF)
MD5 Fingerprint: 192452cd04dec8cbc4ceb8fc0f3ef20c
Created on: 26.11.2016

Tribology letters 63 (2016), No.2, Art.26, 9 pp.
ISSN: 1023-8883
European Commission EC
FP7-PEOPLE; 272619; Topography Evolution
Deutsche Forschungsgemeinschaft DFG
GU 367/30
Deutsche Forschungsgemeinschaft DFG
PA 2023/2
Journal Article, Electronic Publication
Fraunhofer IWM ()
Tribo-induced phase transformation; rehybridization; third body; diamond-like carbon; sperity collision; shear bands; geometric overlap model

The collision of two cylindrical hydrogen-free diamond-like carbon (DLC) asperities with approximately 60 % sp3 hybridization has been studied using classical molecular dynamics. The severity of the collision can be controlled by the impact parameter b that measures the width of the projected overlap of the two cylinders. For a cylinder radius of R = 23 nm, three collisions with b = 0.5 nm, b = 1 nm and b = 2.0 nm are compared. While for the two small b a single shear band between the collision partners and a strongly localized sp2/sp1 hybridised third-body zone between the asperities is observed, the b = 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 the b = 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. For b = 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.