In part 1 it was shown that tribofilms usually are 100 nm thick and exhibit a multiphase nanocrystalline structure. The objective of our modelling efforts was to obtain a better understanding of the sliding behaviour and associated friction properties and to study the impact of internal and external parameters on these properties. The method of movable cellular automata (MCA) was used. The third bodies were considered as aggregates of linked nanoparticles which may decompose and form a layer of granular material, the so-called mechanically mixed layer (MML), if certain fracture criteria are fulfilled. The basic model structure which consists of Fe3O4 nanoparticles with 13 % graphite inclusions was used. In order to assess the robustness of the model the following parameter studies were performed. The pressure range at an asperity contact was varied between 15 and 50 MPa. The mechanical properties of the oxide were varied between brittle and ductile behaviour corresponding to room temperature and high temperature behaviour. The mechanical properties of the soft ingredient were varied ± 50 % of the properties of graphite. The influence of a variety of model parameters on the evolution of the friction coefficient was found.

Andrey Dmitriev, Heinz Kloß, Werner Österle - ISPMS Institute of Strength Physics and Materials Science, BAM Federal Institute for Materials Research and Testing