Fragestellung: Die bisherigen Literaturangaben zur Inzidenz des Frey-Syndroms nach Parotidektomien differieren stark. Ebenso werden Maßnahmen für eine erfolgreiche Behandlung unterschiedlich bewertet.

Temperature gradients, which are introduced into a railway wheel during braking due to friction in the contact zone between wheel and rail can lead to the formation of cracks. This reduces the lifetime or may cause the complete failure of the wheel. In this work, a Nd-YAG-laser thermal fatigue testing system was employed to simulate materials, damage as a result of cyclic temperature gradients in a time-lapse way. Two different kinds of temperature cycles were chosen to differentiate between "thermal shock" which describes the sudden failure, and "thermal fatigue" which means a delayed crack initiation and propagation. Eight ferritic-pearlitic railroad steels have been tested. The experimental evaluation of the damage was effected qualitatively by investigating the failure mechanisms, and quantitatively by detecting numbers of cycles till crack start as well as by determining crack densities, crack depths, and erosion, dependent on the number of cycles. The results obtained from laser-tests show that improving the thermal shock resistance of any railroad steel requires opposite materials' properties to those for improving its thermal fatigue resistance. The materials investigations carried out could establish exemplary connections between thermal shock, thermal fatigue, microstructure, and material's properties.

The efficiency of solar thermal power plants increases rapidly with increasing working temperatures. The problem has to be: solved by the improvement of the materials and via the construction variation of the continuously heat-exposed structural members. Especially the receiver obtains the whole irradiation reflected from the heliostat field. Resistance to high temperatures, to high-temperature corrosion and oxidation, to thermal shock and thermal fatigue load due to changing working temperatures hall to be fulfilled by the receiver materials.Usually, black or coloured materials are preferred because of their higher absorption. In this work, the working temperatures of a gas-heat exchanging receiver reached more than 1600 degrees C because of the employment of a white reflecting material instead of a black absorbing material. The receiver was constructed as a gas-heat conducting exchanger. An irradiation reflecting MgO-powder with argon was used as the heat transport medium. Thermal shock and thermal fatigue conditions could at least be restricted by dynamic controlling.

Laser treatment of ceramic surfaces opens up many new possibilities which have not yet been fully explored. The high dependence oi the material properties on the material surface challenges researchers to try to improve the surface properties of ceramics. In this paper the behaviour of silicon nitride and silicon carbide under Nd-YAG laser irradiation is examined, it was established that laser irradiation may potentially be used to improve the properties of the ceramic surface. The laser irradiation influences the material's resistance to fatigue. To gauge the extent of this influence, in a special testing set-up laser-treated and untreated material samples were exposed to cavitation erosion and the respective mass losses were measured and compared. During laser irradiation different material-dependent mechanisms change the surface of the sample and consequently its resistance to cavitation erosion.

AbstractDie Funktion und der Wirkungsgrad technischer Anlagen wird begrenzt durch die Reaktion eingesetzter Werkstoffe auf die Betriebsbedingungen. Im Hochtemperatureinsatz sind Korrosionsbeständigkeit, Verschleißfestigkeit und Thermoschockfestigkeit ebenso erforderlich wie ausreichende Betriebstemperaturbeständigkeit.Metallische und keramische Werkstoffe erfüllen die Anforderungen oft nicht. Im dynamischen Einsatz kann ein schmiermittel erforderlich sein. Keramische Werkstoffe sind meist nicht ausreichend beständig gegen Schmiermittel. Metalle besitzen zu geringe Oberflächenhärte und sind nicht genügend oxidationsbeständig. Mit metall‐keramischen Werkstoffen, cermets, können die eigenschaften ihrer Bestandteile kombiniert genutzt werden.In dieser Arbeit wird eine cermet/Glasschmiermittel‐Kombination vorgestellt, welche interessante Eigenschaften für den Hochtemperatur‐Einsatz besitzt.

The function and the efficiency of technical plants are limited by the used materials and their behaviour under working conditions.At elevated temperatures, the corrosion and wear resistance and the thermal shock behaviour are as necessary as mechanical stability at high operating temperatures.Metals and ceramics often cannot meet the conditions. Dynamic applications may require lubrication. Ceramics often are not enough resistant to the lubricatings, metals surfaces may be too soft and not very oxidation-resistant. Metal-ceramic materials, -cermets-, use a combination of the properties of their microstructural parts.This paper shows a combination of a cermet and a lubricating glass with interesting aspects for high temperature operation.