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Das tribologische Verhalten wird neben den chemischen und physikalischen Eigenschaften der Reibpartner auch von deren Oberflaechentopographie bestimmt. Um deren Beitrag auf die Reibkraft zu untersuchen, wurden daher definierte Rauheitsstrukturen in Siliziumwafer geaetzt. Reibversuche mit einem Mikrotribometer [1, 2] gaben Aufschluss ueber den Einfluss dieser Strukturen auf das Deformationsverhalten im Kontaktbereich. Mit Hilfe der gewonnenen Daten wurde ein Deformationsmodell entwickelt, das eine Abschaetzung der Reibkraft in Abhaengigkeit von der Rauheit erlaubte. Treten starke Adhaesionskraefte im Reibkontakt auf, ist ein inverter Einfluss der Rauheit auf die Reibkraft zu verzeichnen. Um diesen Verlauf weiter zu charakterisieren, wurden mit einem UHV-AFM Adhaesionsmessungen an strukturierten Siliziumwafern durchgefuehrt. Diese zeigen den Verlauf der Adhaesionskraft in Abhaengigkeit von der Groesse der Kontaktflaeche auf. Ein Vergleich dieser experimentell gefundenen Korrelation mit den klassischen Kontaktmodellen machte dabei den Einfluss der Oberflaechenrauheit auf die Groesse der Adhaesionskraft deutlich. Danach ergab sich, dass bei gleicher Kontaktflaeche, aber unterschiedlicher Rauheit sich die Adhaesionskraefte um bis zu einem Faktor 3 unterscheiden. [1] K. Meine, T. Schneider, D. Spaltmann, E. Santner, Wear, 253, 2002, 725-732 [2] K. Meine, T. Schneider, D. Spaltmann, E. Santner, Wear, 253, 2002, 733-738
The cause and type of solid particle erosion varies across different industries and locations in plants, for instance the particles could be volcanic ash in aero-engines, fly ash in boilers, exfoliated scale in steam turbines or mineral matter in oil excavation. In all cases the durability of materials can be improved through better surface engineering and coatings, but the development of these is restricted also due to lack of generic models. In this respect, the simulation of a single impact with finite element methods using 100.000 knots would take about 15 minutes. In order to simulate an entire particle erosion experiment, up to one billion of such impacts would have to be considered. In order to simulate an entire particle erosion experiment, the current work presents an alternative approach capable of calculating about half a billion impacts on a substrate in less than six hours on a standard PC. The predictions of the simulation will be compared to a steel sample at 600°C eroded by aluminum oxide particles with a velocity around 210 m/s.
The cause and type of solid particle erosion varies across different industries and locations in plants, for instance the particles could be volcanic ash in aero-engines, fly ash in boilers, exfoliated scale in steam turbines or mineral matter in oil excavation. In all cases the durability of materials can be improved through better surface engineering and coatings, but the development of these is restricted also due to lack of generic models. In this respect, the simulation of a single impact with finite element methods using 100.000 knots would take about 15 minutes. In order to simulate an entire particle erosion experiment, up to one billion of such impacts would have to be considered. In order to simulate an entire particle erosion experiment, the current work presents an alternative approach capable of calculating about half a billion impacts on a substrate in less than six hours on a standard PC. The predictions of the simulation will be compared to a steel sample at 600°C eroded by aluminum oxide particles with a velocity around 210 m/s.
In the present work an approach is presented which combines various aspects of the former models with probability considerations. It is used to simulate the impact of more than one billion Alumina particles onto a steel substrate. This approach permits the simulation of an entire erosion experiment on an average PC within about six hours.
This paper shows how Angle-Resolved Scattering can reveal wear on engineered surfaces. The samples studied, three discs made of steel 100Cr6H used in gear wheels in the automotive industry, were assessed after they had undergone ball-on-disc tests. Scattering maps recorded for spatial frequencies from 0.1 µm-1 to 2.7 µm-1 show a contrast inversion around 0.36 µm-1 revealing the wear trace. Besides measurements of rms roughness, where mean values are 20 nm and 24 nm depending on the locations considered, stationarity and isotropy, we demonstrate the ability of the technique to reveal localized wear on this type of surface in a rapid, robust and convenient way. We show that the tool trace is influenced by the load magnitude rather than by the number of oscillation cycles and highlight the key role played by surface roughness in how the sample responds to wear tests.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the picosecond to femtosecond range. During the past few years significantly increasing research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical or chemical properties. In this contribution current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.
Anerkannte Institutionen stellen ihre Kompetenzen auf dem Gebiet tribologischer Charakterisierungen Industrie und Forschung zur Verfügung (https://www.i-tribomat.eu/). Ein Aspekt hierbei ist eine tribologische Datenbank. Um die nötige Qualität der Daten sicherzustellen, sind vereinheitlichte Prozeduren erforderlich, in deren Auswirkungen dieser Vortrag einen Einblick gibt.
The light-weight approach and fuel economy targets in today's automotive engineering require tribosystems, which can withstand higher contact pressures associated with low coefficients of friction. The application of high-performance coatings represents one approach among others. This paper presents some recently developed DLC coatings (a-C:H and ta-C) as well as a novel coating-substrate system (Zr(C,N)) in a benchmark test procedure under slip-rolling conditions in the presence of liquid lubricants. Various coatings with different thickness, interlayer and substrates were evaluated for their slip-rolling resistance in different lubricants at ambient temperature and at 120 °C. Results indicate that some of these coating systems can withstand at least 10 million cycles under initial Hertzian contact pressures of up to Pmax = 3.500 MPa and oil temperatures of at least 120 °C associated with low coefficients of friction under mixed/boundary conditions. Surface of the coatings and the counter bodies were analysed and compared with untreated substrates.