TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Orts Gil, Guillermo A1 - Schneider, Thomas A1 - Ren, H. A1 - Sun, X. T1 - Verification of nanometre-scale modelling of tribofilm sliding behaviour JF - Tribology International N2 - A model based on movable cellular automata has been applied to study the sliding behaviour of tribofilms formed during automotive braking. Since it is not possible yet to determine the composition of real tribofilms quantitatively, final verification of modelling results is needed. This was done by preparing artificial third bodies with compositions and nanostructures matching the ones assumed for modelling. Pin-on-disc tests were performed while applying the artificial third bodies to the contact. The results revealed that not only the structure of the third body but also the amount of the applied normal pressure determines the COF obtained by modelling and that much better correlation between experimental and modelling results was obtained while assuming high normal pressures at asperity contacts. KW - Automotive braking KW - Third body KW - Modelling KW - Sliding simulation PY - 2013 DO - https://doi.org/10.1016/j.triboint.2013.02.018 SN - 0301-679X VL - 62 SP - 155 EP - 162 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-27946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A.I. A1 - Österle, Werner A1 - Kloß, Heinz T1 - Numerical simulation of typical contact situations of brake friction materials JF - Tribology International N2 - In the paper, a model typical for contact situations of automotive brakes is established based on the method of movable cellular automata. The processes taking place at local contacts in an automotive brake system are analysed. Based on microscopic and micro-analytical observations, the following contact situations were simulated: (i) a couple of ferritic steel against pearlitic steel, both covered by an oxide layer mixed with graphite nanoparticles and (ii) the same situation but without oxide layers. The results of calculated mean coefficients of friction of the oxide-on-oxide contact correspond well to expected values for a real braking system, whereas steel-on-steel contact are twice as high. This allows one to make some conclusions; for example, oxide formation will take place more quickly than friction layer elimination, and finally this is responsible for the stabilisation of the coefficient of friction. KW - Friction KW - Primary contact KW - Automotive brake system KW - Numerical simulation KW - Method of movable cellular automata PY - 2008 DO - https://doi.org/10.1016/j.triboint.2007.04.001 SN - 0301-679X VL - 41 IS - 1 SP - 1 EP - 8 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-15841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Kloß, Heinz A1 - Urban, Ingrid A1 - Dmitriev, A.I. T1 - Towards a better understanding of brake friction materials JF - 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. KW - Brake pad KW - Brake disc KW - Composite material KW - Friction layer KW - Third body KW - MCA-modelling PY - 2007 DO - https://doi.org/10.1016/j.wear.2006.12.020 SN - 0043-1648 VL - 263 IS - 7-12 SP - 1189 EP - 1201 PB - Elsevier CY - Amsterdam AN - OPUS4-15735 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Österle, Werner A1 - Kloß, Heinz A1 - Dmitriev, A.I. ED - Bartz, Wilfried J. ED - Friedrich Franek, T1 - Friction control during automotive braking - experimental observations and simulation at the nanometer scale T2 - 3rd Vienna International Conference - Nano-Technology T2 - 3rd Vienna International Conference - Nano-Technology CY - Vienna, Austria DA - 2009-03-18 KW - Bremse KW - Dritter Körper KW - Verschleiß KW - Reibung KW - Nanocharakterisierung KW - Modellierung PY - 2009 SN - 978-3-901657-32-0 SP - 335 EP - 341 AN - OPUS4-19222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Dmitriev, A.I. A1 - Österle, Werner T1 - Numerical modeling of dry friction sliding in pad-disc interface at the nanoscale T2 - 37th Summer school-conference - Advanced problems in mechanics (Proceedings) T2 - 37th Summer school-conference - Advanced problems in mechanics (APM 2009) CY - St. Petersburg, Russia DA - 2009-06-30 PY - 2009 SN - 978-5-91339-029-5 SP - 174 EP - 182 AN - OPUS4-19750 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Kloß, Heinz A1 - Dmitriev, A.I. T1 - Friction control during automotive braking: experimental observations and simulation at nanometer scale JF - Tribology : materials, surfaces & interfaces KW - Friction control KW - Friction film KW - Automotive braking KW - MCA model KW - Nanostructure PY - 2009 DO - https://doi.org/10.1179/175158309X12586382418454 SN - 1751-5831 VL - 3 IS - 4 SP - 196 EP - 202 PB - Maney CY - London AN - OPUS4-20829 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Kloß, Heinz T1 - Does ultra-mild wear play any role for dry friction applications, such as automotive braking? JF - Faraday discussions N2 - Nanostructured third body films and/or storage of wear debris at the surfaces of the first bodies are deemed as prerequisites of sliding under ultra-mild wear conditions. Since such features have been observed experimentally on brake pads and discs, attempts were undertaken to study their sliding behaviour by modelling on the nanoscopic scale with an approach based on Movable Cellular Automata (MCA). The model rendered the possibility to study the influence of different nanostructures systematically and to assess the impact of different brake pad ingredients on the sliding behaviour, velocity accommodation and friction force stabilization at a sliding contact. Besides providing a review on previously published modelling results, some additional new graphs enabling better visualization of dynamic processes are presented. Although ultra-mild wear conditions were considered to be essential for achieving the desired tribological properties, transitions to mesoscopic and macroscopic wear mechanisms were studied as well. The final conclusion is that ultra-mild wear and corresponding smooth sliding behaviour play an important role during automotive braking, even though temporarily and locally events of severe wear may cause friction instabilities, surface damage and release of coarse wear particles. KW - Dry friction KW - Ultra-mild wear KW - Third body KW - MCA-model KW - Simulation PY - 2012 DO - https://doi.org/10.1039/c2fd00117a SN - 1359-6640 SN - 1364-5498 VL - 156 IS - 0 SP - 159 EP - 171 PB - Soc. CY - Cambridge [u.a.] AN - OPUS4-26822 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Kloß, Heinz T1 - Possible impacts of third body nanostructure on friction performance during dry sliding determined by computer simulation based on the method of movable cellular automata JF - Tribology International N2 - The tribological properties of nanostructured surface films formed during dry sliding, for example during automotive braking, were determined by modelling using the method of movable cellular automata. Starting from a basic model structure, consisting of magnetite with 13% graphite inclusions, the impact of additional soft and hard particles of different size and volume fraction was studied systematically. It was revealed that agglomerates of soft particles decomposed and finally mixed with the oxide in the same way as single nanoparticles. On the other hand, agglomerates of hard particles mixed with the other components without decomposing. Whereas increasing the amount of soft components in the third body lowered the coefficient of friction, the opposite occurred with the hard particles. The boundary conditions for obtaining smooth sliding conditions with minor fluctuations between friction forces at successive time steps could be defined. In addition to features of the nanostructure, the applied normal pressure impacted modelling results. Within the parameter range of smooth sliding behaviour, increasing pressure induced thicker granular interface layers, which lead to a slight decrease of the coefficient of friction. Changing the amount of soft or hard particles did not change this pressure dependency but only the friction level. KW - MCA-modelling KW - Third body KW - Nanoparticles KW - Dry friction PY - 2012 DO - https://doi.org/10.1016/j.triboint.2011.11.018 SN - 0301-679X VL - 48 SP - 128 EP - 136 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-25469 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Deutsch, Cornelius A1 - Gradt, Thomas A1 - Orts Gil, Guillermo A1 - Schneider, Thomas A1 - Dmitriev, A.I. T1 - Tribological screening tests for the selection of raw materials for automotive brake pad formulations JF - Tribology International N2 - A modified pin-on-disc test was applied to determine tribological properties of typical brake pad constituents. Ball-milling of these ingredients together with iron oxide and graphite provided model materials displaying the main features of real third bodies. Solid lubricants like graphite affected the friction and wear behaviour of Fe3O4 powders considerably whereas further addition of hard nanoparticles induced only minor effects. This was corroborated by comparison with modelling results. MoS2 played a dual role. Depending on special conditions, this ingredient either reduced or increased friction. The latter could be explained, after nanoscopic characterization, by oxidation and destruction of the wear-protecting tribofilm. KW - Brake pad formulation KW - Raw materials KW - Third body KW - Pin-on-disc test PY - 2014 DO - https://doi.org/10.1016/j.triboint.2014.01.017 SN - 0301-679X VL - 73 SP - 148 EP - 155 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-30221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A.I. A1 - Österle, Werner A1 - Kloß, Heinz T1 - Nano-scale modeling of pad-disc interface. The influence of copper as a pad ingredient. T2 - JEF 2010 - 6th European conference on braking (Proceedings) T2 - JEF 2010 - 6th European conference on braking CY - Lille, France DA - 2010-11-24 KW - Friction layer KW - Copper particles KW - MCA-modelling PY - 2010 SP - 1 EP - 6(?) AN - OPUS4-22656 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Österle, Werner A1 - Kloß, Heinz A1 - Dmitriev, A.I. T1 - Modeling of Friction Evolution and Assessment of Impacts on Vibration Excitation at the Pad-Disc Interface T2 - 26th Annual Brake Colloquium & Exhibition, October 12-15, 2008, San Antonio, Texas, USA T2 - 26th Annual Brake Colloquium & Exhibition CY - San Antonio, Texas, USA DA - 2008-10-12 KW - Friction materials KW - MCA-modeling KW - Friction films KW - Noise propensity KW - Friction-induced vibrations PY - 2008 SN - 978-0-7680-2097-7 IS - 2008-01-2582 SP - 303 EP - 311 AN - OPUS4-18695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A.I. A1 - Österle, Werner A1 - Kloß, Heinz T1 - Numerical Simulation of Mechanically Mixed Layer Formation at Local Contacts of an Automotive Brake System JF - Tribology transactions KW - Nanotribology KW - Automotive Brakes KW - Dynamic Modelling KW - Friction Mechanisms KW - Mechanically Mixed Layer KW - Movable Cellular Automata PY - 2008 DO - https://doi.org/10.1080/10.40.2000802380314 SN - 1040-2004 SN - 1547-397X VL - 51 SP - 1 EP - 7 PB - Taylor & Francis CY - Philadelphia, Pa. AN - OPUS4-18696 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A.I. A1 - Smolin, A.Y. A1 - Psakhie, S.G. A1 - Österle, Werner A1 - Kloß, Heinz A1 - Popov, V.L. T1 - Computer modeling of local tribological contacts by the example of the automotive brake friction pair JF - Physical mesomechanics N2 - In the paper the method of discrete modeling (movable cellular automata method) and combined discrete-continuous description of the simulated medium are used to analyze processes occurring in the local contact of the automotive brake system. The characteristic size of the considered region is 1.5 ?m. The following contact situation is simulated: steel fiber coated by an iron oxide film as the brake pad and pearlitic steel also coated by an iron oxide layer as the disc. On the assumption of oxide layer wearing we simulate the iron oxide - iron oxide, iron oxide - metal and metal - metal contacts. The calculation results for the friction coefficient for various contact situations give quite adequate values. For example, for the oxide - oxide system the calculated coefficient is approximately equal to 0.4, while for the metal - metal contact the obtained value varies from 0.7 to 0.9. Analysis of a set of the obtained results allows concluding that oxide is formed more rapidly than the sliding layer, which in turn makes the friction coefficient value stabilized. PY - 2008 DO - https://doi.org/10.1016/j.physme.2008.03.008 SN - 1029-9599 VL - 11 IS - 1-2 SP - 73 EP - 84 PB - Inst. of Strength Physics and Materials Science SB RAS CY - Tomsk AN - OPUS4-18698 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Österle, Werner A1 - Müller, Urs A1 - Desplanques, Y. A1 - Bulthé, A.-L. A1 - Degallaix, G. A1 - Dmitriev, A.I. T1 - 3rd Body formation of two different brake pad materials designed for railway application T2 - 5th European Conference on Braking (JEF 2006), November 8-9, 2006, Lille, France (Proceedings) T2 - 5th European Conference on Braking (JEF 2006) CY - Lille, France DA - 2006-11-08 PY - 2006 SP - 107 EP - 115 AN - OPUS4-18699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Urban, Ingrid ED - Jayashree Bijwe, T1 - Characterization of up to date brake friction materials T2 - IWAAFC-1, International Workshop on Advances in Asbestos free Friction Composites, January 5-6, 2006, Delhi, India (Proceedings) T2 - IWAAFC-1, International Workshop on Advances in Asbestos free Friction Composites CY - Delhi, India DA - 2006-01-05 PY - 2006 SP - 21 EP - 35 CY - Delhi, India AN - OPUS4-18700 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Kloß, Heinz ED - Jayashree Bijwe, T1 - Basic considerations for the development of friction materials T2 - Proceedings of the IWAAFC-2, International Workshop on Advances in Asbestos-free Friction Composites T2 - IWAAFC-2, International Workshop on Advances in Asbestos-free Friction Composites CY - Delhi, India DA - 2008-02-07 PY - 2008 SP - 24 EP - 51 PB - Indian Academy of Sciences CY - Delhi, India AN - OPUS4-18701 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A.I. A1 - Österle, Werner T1 - Sliding simulations with variable amounts of copper and graphite mixed with magnetite T2 - Proceedings EuroBrake 2016 N2 - Copper is one of the most important components in brake pads and its amount can reach up to 14%. In spite of a number of positive features copper usage in brake pad formulations has recently become the subject of considerable discussions, primarily due to concerns about potential risks related to environmental impacts of copper particles. So, for developing new pad formulations with possible replacements of copper content, it is very important to understand the functionality of copper additions to brake friction materials. In the paper theoretical investigation of the role of copper as a pad ingredient was carried out on the basis of modelling by the method of movable cellular automata (MCA). Our previous studies show that copper as a constituent of the tribofilm formed during braking provides smooth sliding by forming a granular layer of mechanically mixed materials from the friction layers. In the present study the concentration of copper particles in a Fe3O4-matrix was varied systematically in the range 5.5-28 vol. % and compared to mixtures with the same amount of graphite nanoparticles. The sliding simulations were performed while assuming material properties at 500°C in order to assess the beneficial role of copper during severe braking conditions corresponding to fading cycles during dynamometer testing. T2 - EuroBrake 2016 CY - Milano, Italy DA - 13.06.2016 KW - Movable cellular automata KW - Copper KW - Sliding simulation KW - Third body KW - Tribofilm PY - 2016 UR - www.eurobrake.net VL - EB2016-SVM-054 SP - 1 EP - 7 PB - FISITA AN - OPUS4-37938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A.I. A1 - Nikonov, A.Y. A1 - Österle, Werner T1 - Multiscale modeling of low friction sliding behavior of a hybrid epoxy-matrix nanocomposite T2 - Procedia Structural Integrity N2 - The method of movable cellular automata (MCA) and method of molecular dynamics (MD) were applied to simulate the friction and sliding behavior of model-tribofilms formed from a nanocomposite consisting of an epoxy matrix, 10 vol % micron-sized carbon fibers and 5 vol. % silica nanoparticles. Whereas MCA considered the tribofilm as an agglomerate of silica nanoparticles released from the composite and mixed with graphite particles, MD simulated the sliding behavior of an amorphous silica layer supported by stiff crystalline substrates on both sides. The MCA model provided reasonable quantitative results which corroborate experimental findings at moderate stressing conditions. The very low coefficient of friction observed experimentally under severe stressing conditions was not explained by this model. This could be attributed to the lack of mechanical data at the high temperature expected under these conditions. Although based on a simpler assumption of the tribofilm composition, MD-modelling could be easily applied to the expected high flash temperature and was able to predict friction reduction and smooth sliding under these conditions. T2 - 21st European Conference on Fracture ECF21 CY - Catania, Italy DA - 20.06.2016 KW - Silica nanoparticle KW - Hybrid composite KW - Tribofilm KW - Molecular dynamics KW - Movable cellular automata PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-379402 DO - https://doi.org/10.1016/j.prostr.2016.06.294 VL - 2 SP - 2347 EP - 2354 PB - Elsevier Ltd. AN - OPUS4-37940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Gradt, Thomas A1 - Häusler, Ines A1 - Hammouri, Basem A1 - Morales Guzman, Pablo Israel A1 - Wetzel, B. A1 - Yigit, D. A1 - Zhang, G. T1 - Exploring the beneficial role of tribofilms formed from an epoxy-based hybrid nanocomposite JF - Tribology International N2 - The composition and nanostructure of a beneficial tribofilm formed during sliding of a hybrid nanocomposite against steel were characterized comprehensively. A similar nanostructure was produced by high energy ball milling of the three identified tribofilm constituents: silica, hematite and graphite. By supplying powders to a pin-on-disc test it has been shown that neither silica, nor hematite, nor a mixture of both provide the low coefficient of friction (COF) observed for the hybrid composite. Only if graphite was blended with the oxides, the low COF was obtained. Thus, a film of finely dispersed stable inorganic wear products containing 15 vol% graphite provides low friction and wear in the considered case. KW - TEM KW - Nanocomposite KW - Tribofilm KW - Ball milling KW - Pin-on-disc test PY - 2015 DO - https://doi.org/10.1016/j.triboint.2015.03.006 SN - 0301-679X VL - 88 SP - 126 EP - 134 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-33035 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Giovannozzi, A. A1 - Gradt, Thomas A1 - Häusler, Ines A1 - Rossi, A. A1 - Wetzel, B. A1 - Zhang, G. A1 - Dmitriev, A.I. T1 - Exploring the potential of Raman spectroscopy for the identification of silicone oil residue and wear scar characterization for the assessment of tribofilm functionality JF - Tribology International N2 - We applied a combination of Raman spectroscopy (RS) and cross-sectional transmission electron microscopy (X-TEM) to identify silicone oil residues and tribofilms at steel disc surfaces after tribological testing. Neither chemical cleaning nor mechanical removal of a 50 µm thick surface layer produced a surface without any silicone residue. Nevertheless, long-term tribological properties are not affected due to silicone degradation which has been proved by Raman spectroscopy. Excellent anti-wear and anti-friction properties of a nanocomposite at severe stressing conditions correlated with the formation of a silica-based tribofilm containing amorphous and graphite-like carbon nanoparticles. Since reliable carbon quantification by analytical TEM is difficult, RS is a useful complementary method for carbon identification at wear scars. KW - Raman spectroscopy KW - Cross-sectional TEM KW - Silicone oil residue KW - Tribofilm PY - 2015 DO - https://doi.org/10.1016/j.triboint.2015.04.046 SN - 0301-679X VL - 90 SP - 481 EP - 490 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-33421 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -