Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Sammelband (5)
- Beitrag zu einem Tagungsband (5)
- Zeitschriftenartikel (4)
- Buchkapitel (2)
- Vortrag (2)
- Sonstiges (1)
Schlagworte
- Tribologie (19) (entfernen)
Organisationseinheit der BAM
- 9 Komponentensicherheit (3)
- 9.5 Tribologie und Verschleißschutz (3)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.4 Prozessanalytik (1)
- 2 Prozess- und Anlagensicherheit (1)
- 2.0 Abteilungsleitung und andere (1)
- 2.1 Sicherheit von Energieträgern (1)
- 3 Gefahrgutumschließungen; Energiespeicher (1)
- 3.0 Abteilungsleitung und andere (1)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (1)
Eingeladener Vortrag
- nein (2)
In a future energy supply system based on renewable sources hydrogen technology will play a key role. Because the amount of energy from renewable sources, such as wind or solar power, differs seasonally and regionally, an energy storage method is necessary.
Hydrogen, as an environmentally friendly energy carrier, can fill this gap in an ideal way, in particular for mobile applications (Wurster et al., 2009). Already today, in Germany the amount of hydrogen as a byproduct in chemical industry is enough for fuelling about 1 Mio passenger cars1. Excess electrical power can be used to produce hydrogen by electrolysis. On demand, this hydrogen can be used for mobile or stationary fuel cells. Beside this new developing technology, hydrogen is used as fuel for rocket engines and in chemical industry since a long time. Table 1 comprises some physical parameters of hydrogen. It can be seen that hydrogen gas has a very low density which makes storage at high pressure or in liquid form (LH2) necessary.
This paper presents the mechanical and tribological properties of
Polytetrafluoroethylene (PTFE) and Polyetheretherketone (PEEK)
matrix composites filled with short carbon fibers in cryogenic
environments. Tensile tests were performed at room temperature (RT)
in air and in LN2. Tribological experiments were carried out with a
pin-on-disc configuration at RT, in LN2, in LH2 and in LHe. PEEK
composites have a better tribological performance than PTFE materials
especially regarding the wear resistance.
Supporting elements between large superconducting magnets like the field coils in WENDELSTEIN 7-X have to sustain high loads while allowing a certain amount of tangential movement without any stick-slip motion. In model tests with reciprocating friction in liquid helium and vacuum a PVD-MoS2-coating has proven its suitability for these components. It showed a very stable sliding behaviour with a friction coefficient below 0.1 without coating failure under all test conditions.
For tribological components working under extreme
conditions, such as vacuum, or broad temperature
ranges, it is often a problem to achieve acceptable
durability of their friction parts. Thus, new material
requirements are involved for these tribo-systems, in
particular regarding operability and reliability. At BAM,
several projects were conducted in the recent years,
dealing with the tribological properties of friction
couples at cryogenic temperature and in vacuum
environment. This paper describes the vacuum and ultra
high vacuum tribometers constructed at BAM and
presents experiments carried out with polymer
composites. The experiments presented were performed
with PEEK, filled with solid lubricants, against 304
steel with a pin-on-disc configuration in oscillating
sliding. Friction tests were carried out in vacuum in the
temperature range between -40°C and +160°C and in
ultra high vacuum at room temperature.
Spacers and supports belong to the critical elements in the structure of a nuclear fusion device, particularly, when they are installed in the vacuum or superconducting magnet system of the reactor. These supports have to sustain high loads while allowing a certain amount of tangential movement with low friction and without any stick-slip motion. Vacuum and cryogenic environments are extremely hostile for smooth sliding systems, because conventional liquid lubricants cannot be employed, and only a very limited number of materials for dry sliding systems under these conditions are available. In order to test the friction behaviour of support elements in the field coils of the fusion experiment WENDELSTEIN 7-X, a test rig was build which allows testing in liquid helium environment at 4.2 K, with a normal force up to 150 kN, and a sliding velocity of 0.1 mm/s in oscillating motion. First tests have shown that the apparatus is appropriate for simulating the sliding behaviour of support elements. As an example, a result of an earlier model test of an MoS2-coating is shown.
Cryogenic solid lubrication
(2013)
Vakuumtribologie
(2010)
Tieftemperaturtribologie
(2010)
Der Festschmierstoff Molybdändisulfid ist insbesondere für Extremanwendungen ein gerne eingesetzter Werkstoff, problematisch ist jedoch der negative Einfluss von Feuchtigkeit. Bei mittels PVD-Verfahren abgeschiedenen MoS2-Schichten ergibt sich jedoch die Möglichkeit, durch Anpassung der Beschichtungsparameter vorwiegend basal ausgerichtete Schichten herzustellen, die auch an Luft ein verbessertes tribologisches Verhalten zeigen.
Verschleißfeste Kohlenstoffschichten mit niedriger Reibung sind hervorragend für Anwendungen in der Erdgas- und Wasserstofftechnologie geeignet. Einige Varianten versagen jedoch in inerter Umgebung, was für die praktische Anwendung sehr nachteilig ist. Im Vortrag werden Beispiele aus Modellversuchen für verschiedene Varianten, auch für Flüssigmethan-Umgebung gezeigt.
Influence of solid lubricant fillers on the tribological behaviour of peek composites in vacuum
(2009)
The magnetic plasma confinement system of the nuclear fusion experiment “Wendelstein 7-X”, which recently produced the first plasma, consists of 20 planar and 50 non-planar superconducting coils. To keep them precisely in position, these coils contact each other at special support elements. The supports are operated in high vacuum at a temperature of about 4 K, and when the magnetic field is ramped up, forces up to 1500 kN and sliding motion of some mm occurs. Because mechanical disturbances may cause severe failures, only low friction without any stick-slip behaviour is tolerable. In pre-tests a PVD-MoS2-coating had proven to be the optimum solution. It was tested with downsized samples in reciprocating motion in liquid nitrogen (T = 77 K) and liquid helium (T = 4,2 K). In long-term tests in liquid nitrogen this coating showed stable sliding for up to 14.900 friction cycles without coating failure. However, in liquid helium an unexpected stick-slip effect occurred, whose origin could not be clarified so far.
The solid lubricant molybdenum disulfide is a well known material for extreme conditions where conventional oil or grease lubrication is not feasible (vacuum, high pressures). However, under reactive environments e.g. high humidity or hydrogen MoS2 is prone to premature failure. By using a PVD process, deposition parameters can be optimized to gain coatings with a more textured structure orienting the basal planes parallel to the Substrate surface, A similar concept has been used by Koch et al. for coatings developed to withstand the extreme operational conditions of the WENDELSTEIN W7-X fusion experiment. Therefore, an improved tribological behavior even under adverse conditions can be achieved.
The prediction of the properties of the materials used in the operation of components is of enormous importance, in order to accelerate the development process of new components. To evaluate new materials in terms of their performance (in a component), the development of new innovative methods is necessary. These methods can also be summarized under the term lab-to-field or materials – upscaling, meaning materials being characterised in a laboratory and their properties being upscaled to the component performance by means of e.g. simulation. i-TRIBOMAT is a EU funded project (H2020, GA Nr. 814494) aiming at building an Open Innovation Test Bed for tribological material characterization and offering corresponding services from tribological characterization of new materials to simulation models for predicting the performance of industrial components. By bundling the infrastructure, know-how for characterization and building a digital platform, i-TRIBOMAT becomes the world’s largest open innovation test bed for tribological material characterization.
Die BAM ist nahezu über die gesamte Wertschöpfungskette hinweg wissenschaftlich tätig. Von der sicheren und effizienten Wasserstofferzeugung (POWER-to-GAS), über die (Zwischen-)Speicherung von Wasserstoff in Druckgasspeichern bis hin zum Transport bspw. mittels Trailerfahrzeug zum Endverbraucher.
Komplettiert werden die Aktivitäten der BAM durch die sicherheitstechnische Beurteilung von wasserstoffhaltigen Gasgemischen, die Verträglichkeitsbewertung von Werkstoffen bis hin zur Detektion von Wasserstoffkonzentrationen über geeignete Sensorik, auch mittels ferngesteuerter Messdrohnen (sog. UAV-Drohnen).
Zudem untersucht die BAM proaktiv Schadensrisiken und Unfallszenarien für die Sicherheitsbetrachtung, um mögliche Schwachstellen aufzeigen und potenzielle Gefährdungen erkennen zu können.