Some results of numerical study on the role of tribofilms formed during automotive braking

As it was shown in our experimental observation tribofilms generated during braking usually are 100 nm thick and exhibit a multiphase nanocrystalline structure. The objective of our modeling was to obtain a better understanding of the sliding behavior and associated friction properties and to study the impact of internal and external parameters on these properties. The third bodies were considered as aggregates of linked nanoparticles which may decompose and form a layer of granular material. 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 mechanical properties of the oxide were varied between brittle and ductile behaviour corresponding to room temperature and high temperature behavior. 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.