TY - JOUR A1 - Österle, Werner A1 - Kloß, Heinz A1 - Urban, Ingrid A1 - Dmitriev, A.I. T1 - Towards a better understanding of brake friction materials T2 - Wear N2 - This work focuses on surface changes induced by repeated brake applications and tries to provide explanations, how such material modifications might affect friction and wear properties of automotive disc brakes. Surface films were investigated locally by transmission electron microscopy (TEM) after having prepared thin cross-sections with a focused ion beam instrument (FIB). Since the observed friction layers revealed a nanocrystalline structure, modelling with the method of movable cellular automata (MCA) was performed by assuming an array of linked nanometer-sized particles. In spite of complicated material combinations at the pad surface, two very characteristic features were always observed at both the pad and disc surface, namely a steel constituent—either ferritic (pad) or pearlitic (disc), partly covered with patches of nanocrystalline iron oxide, on a zone of severe plastic deformation with fragmented grain structure. When using an automata size of 10 nm, reasonable values for the mean coefficient of friction (COF) were obtained, namely 0.35 and 0.85 for oxide-on-oxide and metal-on-metal contacts, respectively. Immediately after brake application mass-mixing and bond-breaking was observed within a narrow zone at both surfaces. PB - Elsevier CY - Amsterdam KW - Brake pad KW - Brake disc KW - Composite material KW - Friction layer KW - Third body KW - MCA-modelling PY - 2007 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/15735 AN - OPUS4-15735 SN - 0043-1648 VL - 263 IS - 7-12 SP - 1189 EP - 1201 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany