Methoden der in-situ Visualisierung der Reibzonendynamik trockenlaufender Reibpaarungen unter Ergänzung physikalischer und chemischer Charakterisierungen der Reibpartner

Gramstat, Sebastian GND

Die vorliegende Arbeit charakterisiert die Wirkmechanismen der Reibschicht trockenlaufender Reibpaarungen. Mittels in-situ Visualisierungsmethoden wird die Dynamik der Patchlebenszyklen über eine Bremsungsdauer ermittelt. Zudem werden die Bewegungsgeschwindigkeiten und –bahnen sowie die Verweildauern der Abriebpartikel in der Reibzone charakterisiert. Der Charakterisierungsansatz, der zudem lokal aufgelöste Belagtopographie-, Kompressibilitäts- und Porositätsanalysen sowie chemische Analysen vorsieht, offenbart ebenfalls Zusammenhänge zwischen der Patchdynamik und der Reibbelagphysik und –chemie in Bezug auf das tribologische und thermische Verhalten. Letzteres erlaubt es, Hitzeflecken in der Reibzone zu beschreiben, indem ihre Anzahl und Flächen dynamisch bestimmt werden. Mittels der vorgestellten Methode ist es möglich, die Dynamik und Wirkmechanismen vom einzelnen Patch über verschiedene Patchzonen bis hin zur kompletten Reibzone (inklusive Reibringverlagerungen) zu charakterisieren.

The tribological behaviour of dry-running friction couples is till today not entirely describable. The need of the knowledge of that what happens inside the friction zone during a brake application is enormous. Hence it is an essential objective of the present work to overcome existing limits of in-situ investigations of the friction processes on a multi scale level (nano, micro, macro) to characterize the mechanisms of the friction layer. Therefore enhanced in-situ visualisation investigations were undertaken by the use of especially developed brake discs and original brake linings of passenger cars. The latter include the consideration of different compositions such as ECE, NAO and copper-free ECE formulations. As a result the comparability of the knowledge obtained from the in-situ test concept to conventional friction couples (cast iron disc – organic brake lining) can be stated what underlines the capability and significance of the novel method. Direct analogies regarding the number, size and shape of patches can be observed by the appeared patch behaviour. Using the visualisation and complementary analysis methods it is for the first time feasible to characterize the dynamic of the patch life cycles as a function of the surface area over the braking time. Moreover the force transmitting friction zone surfaces between brake applications were determined and allow conclusions regarding the onset of residual torques. Beside patch analyses the wear particle velocities, traces and dwell times inside the friction zone could be determined for the first time. It was shown that the particles not only move much slower compared to the rotor speed but also that the lining composition has a crucial influence on the development of particle traces and the mutual interaction of the particle motion behaviour. The characterization approach which also includes additional local resolved brake pad topography, compressibility and porosity analyses (by the use of three dimensional computer tomography) as well as chemical analyses (using an EDX analyser) reveals moreover important relationships between the established patch dynamic and the pad physics and chemistry regarding the tribological (dry and wet friction processes) and thermal (thermoelastic instabilities) behaviour. The latter allows for the first time to describe hot spots inside the friction zone by the dynamic determination of their number and surface areas. By means of the presented investigation method it is now feasible to characterize the dynamics and mechanisms from the single patch over certain patch zones finally to the entire friction zone (inclusive friction ring shifts).

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Gramstat, Sebastian: Methoden der in-situ Visualisierung der Reibzonendynamik trockenlaufender Reibpaarungen unter Ergänzung physikalischer und chemischer Charakterisierungen der Reibpartner. Ilmenau 2014. Universitätsverlag Ilmenau.

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