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- Third body (4)
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- Movable cellular automata (3)
- Wear (2)
- 9-12% Cr-steels (1)
- Ball milling (1)
- Beschichtung (1)
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- Brake pad formulation (1)
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- Copper (1)
- Copper particles (1)
- Corrosion gases (1)
- Dry friction (1)
- FIB (1)
- Friction film (1)
- Friction layer (1)
- HIP-Simulation (1)
- Heat accumulation (1)
- High temperature corrosion (1)
- Hybrid composite (1)
- Hydrogen transport (1)
- Lattice (1)
- Local structural transformations (1)
- MCA-modelling (1)
- Metal sulphides (1)
- Mild steels (1)
- Modelling (1)
- Molecular dynamics (1)
- Nanoparticles (1)
- Nanostructure (1)
- Numerical simulation (1)
- Oxyfuel combustion (1)
- PMC-pad (1)
- Pad ingredients (1)
- Pin-on-disc test (1)
- Polymer matrix composite (1)
- Reibung (1)
- SEM (1)
- SM-pad (1)
- Silica nanoparticle (1)
- Silica nanoparticles (1)
- Size-distribution (1)
- Sliding simulation (1)
- Successive braking (1)
- Thermal localisation (1)
- Third body film (1)
- Verschleiß (1)
Phasenbildung in Metall-Halbleiterkontaktschichten und Präparationstechnik für TEM-Untersuchung
(1995)
Besides carbon, metal sulphides are used in every standard brake pad formulation as friction stabilisers. In order to investigate their impact, various powder mixtures were tribologically stressed in a pin-on-disc device in order to produce and test artificial third bodies. containing the three main components of a real friction film, namely magnetite, graphite and a metal sulphide of interest. Since the sliding behaviour is influenced by the relative humidity the powder mixtures are tested at low, medium and high moisture levels. The tests revealed that the presence of graphite dominates the friction behaviour as well as the humidity sensitivity.
The powders were prepared by either manual mixing or high energy ball-milling. Interestingly, all ball-milled blends provided coefficients of friction within the desired range for braking, which was attributed to the effect of zirconia particles from wear debris of the milling balls. The zirconia particles prevent the formation of solid lubricant films on the surfaces and support a homogeneous mixture of all constituents of the powder. Optimum brake performance is gained by an optimum combination of solid lubricants and abrasives.
In order to obtain a better understanding of the role of tribofilms during automotive braking, their structures were investigated and the essential features identified.
Next, different ingredient combinations were studied by preparing some model materials with simpler compositions than real tribofilms. A test method was developed for verifying the tribological properties of the model materials and for comparison with results obtained with numerical sliding simulations of such structures. Prerequisites of good brake Performance properties were identified. Although the coefficient of friction could be varied in a wide ränge, smooth sliding conditions could only be achieved with values smaller than 0.4. Tests with artificial third body powders turned out to be useful as screening method for the selection of raw materials for brake pad formulations.
Tribofilms formed during dry sliding usually exhibit a nanocrystalline structure and complicated composition. In the present study, tribofilms consisting mainly of a solid lubricant, namely graphite nanoparticles, are considered. Systems providing such tribofilms are candidates for anti-friction applications. Since sliding action always leads to mixing of the materials at both sides of the tribological interface, it was of major interest to study the impact of different amounts of a hard constituent, SiC in the considered case, within the soft matrix systematically. Furthermore, the impact of normal pressure was considered. A mechanically mixed layer was observed for the whole range of normal pressures and SiC volume fractions. The calculated coefficient of friction decreased significantly with increasing thickness of this layer but was only marginally affected by SiC volume fraction, which is good news for anti-friction applications.