Towards a Control Theory Interpretation of Material Ingredients' Impact on Friction Performance

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Towards a Control Theory Interpretation of Material Ingredients' Impact on Friction Performance

Ostermeyer, Georg-Peter / Bode, Kai

Brake pad materials in today's commercially marketed vehicles are usually complex phenolic resin based composites with numerous ingredients. Since the abandonment of asbestos fibers, different material classes evolved in Europe (low steel), North America (semimet) and Asia (NAO), which specifically meet the requirements of the respective market [ 1 ]. For these complex materials, no a-priori prediction of friction and wear performance is possible today [ 2 ]. Research over the past decade revealed that friction power and wear debris are interrelated [ 3 ] and that the topography of the friction layer shows a very rich dynamic [ 4 ]. The respective processes can be well described with a family of dynamic friction laws, which is suitable for the description of AK-Master test results [ 5 ], as well as for the understanding of history dependent high frequency effects. Up to now, we have modeled these processes by classical cellular automata methods, which picture the surface in microscopic details [ 6 ]. Recent investigations indicate that the generic interactions within these boundary layer dynamics can be interpreted as stable control loops, nature uses to protect surfaces in frictional contacts. This approach opens new insights into the interrelation between material composition and friction for brake pads, where the ingredients modulate the parameters of the control loops.