TY - JOUR A1 - Dmitriev, Andrey A1 - Ă–sterle, Werner T1 - Modeling of brake pad-disc interface with emphasis to dynamics and deformation of structures JF - Tribology International N2 - The frictional behavior at local contacts in an automotive brake system was analysed on the basis of computer simulation by movable cellular automata method. The boundary conditions of the model were adjusted to experimental observations obtained by TEM. The model proved to be adequate for simulating mechanical mixing and velocity accommodation at the pad-disc interface. Dynamics of particle interaction were visualized by showing rotation angles and velocity vectors. The model provided information on the development of plastic deformation for metal-on-metal contacts and on crack formation at graphite lamellae of cast iron disc. Results are in agreement with conventional friction theories. KW - Nanotribology KW - Pad-disc interface KW - Simulation KW - Mechanically mixed layer PY - 2010 DO - https://doi.org/10.1016/j.triboint.2009.10.012 SN - 0301-679X VL - 43 IS - 4 SP - 719 EP - 727 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-20876 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ă–sterle, Werner A1 - Dmitriev, Andrey T1 - Functionality of conventional brake friction materials - Perceptions from findings observed at different length scales JF - Wear N2 - Automotive braking is based on dry friction between fixed pads and a rotating disc. Besides macroscopic thermo-physical properties, the development of topographic features on the mesoscopic scale and the nanostructure of the third body formed by wear processes, determine brake performance properties. Whereas modelling on the atomistic scale is suitable to understand mechanisms leading to nanocrystalline surface films, the properties of such films can be assessed best with a model based on movable cellular automata (MCA). It turned out that the presence of at least 10% of soft nanoinclusions is most essential in respect to smooth sliding conditions. It made no major difference whether graphite or copper particles were assumed as soft nanoinclusions. The third body material is not only the stuff which spreads over contact areas, but it also contributes to contact size by wear particle compaction and formation of secondary contact areas. The evolution of contact size is the major feature of mesoscopic modelling and thus it is capable to model and explain dynamic changes of the coefficient of friction (COF) during certain brake operations. Although it is still ambiguous in many cases which feature has the major impact on friction behaviour, the following conclusions can be drawn. The reinforcing ingredients of the pad material serve as primary contact sites and thus define the starting condition for mesoscopic simulations. A certain amount of wear is necessary to provide a third body which is capable to form secondary contact sites and friction layers screening the first body materials. The composition and nanostructure of the third body is important as well, because it determines the friction level and is responsible for smooth sliding conditions. KW - Nanostructure KW - Microstructure KW - Mesostructure KW - Macrostructure KW - Modelling KW - Simulation PY - 2011 DO - https://doi.org/10.1016/j.wear.2010.11.035 SN - 0043-1648 VL - 271 IS - 9-10 SP - 2198 EP - 2207 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-24177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -