Vergleich der mittleren Bewegungen in der babylonischen,griechischen und indischen Astronomie

The mean motions of sun, moon and planets according to Greek authors are compared with those derived from Babylonian and Indian sources. From this comparison, conclusions concerning dependence can be drawn.     

Gas- und Plasmanitrieren der (α + β)- Titanlegierung TiAl6V4. Vergleichende Untersuchungen zu Schichtaufbau und Schichteigenschaften

The usually low wear resistance of titanium materials can be increased by the thermochemical surface treatment nitriding. In result of comparative investigations of gas and plasma nitriding it will be shown that it is possible to obtain a specific variation of the properties in the highly stressed case by means of these both technologies on example of the (α + β) alloy Ti-6Al-4V. Gas and plasma nitriding was carried out in the temperature range from 650 to 800°C over 4 to 48 h in different gas atmospheres, i. e. 100% NH₃ (gas), 100% N₂ (gas and plasma), 20% H₂ + 80% N₂ and 20% Ar + 20% H₂ (plasma). The temperature range was fixed in the middle of (α + β) region, because the core properties are influenced negative in the field of β-transustemperature. The relations between the applied nitriding technologies, the layer structure (chemical, phases, geometrical) and selected layer properties (microroughness, microhardness, fracture and wear behaviour) are described.     

Kavitationsuntersuchungen an Werkstoffen und Beschichtungen – Vergleich verschiedener Auswerte‐verfahren und Gegenüberstellung der Kavitationserosion von EN‐GJS‐600‐3, G‐CuAl8Mn8 und GX4CrNi13‐4 + QT

Material damages in fluid flow machines which are charged by cavitation cause costs due to service and downtime of the affected machines. Therefore the aim of engineering needs to be cutback of cavitation by the optimization of fluid flows and suitable selection of materials relating to cavitation. Cavitation has to be moved to temporally uncritical time ranges. This is why the cavitation resistance of materials and coatings that may be used to increase product durability need to be tested. In regard to extensive test series the adequacy of different evaluation methods like touch slice measurement, white light profilometry, weighing and optical comparison got tested in regard to suggest a suiting evaluation method for all possible applications. The results are showing that for evaluation of material tests the weighing method with a highly resolving scale suites best. In fact the use of white light profilometry is much better for accurate evaluation of coating tests. The optical comparison method supports quick comparisons of specimen in both cases. Broader research shows the impressive cavitation resistance of G‐CuAl8Mn8 compared to the probed steel specimen.     

Relaxationsverhalten des Werkstoffs X6 CrNi 18 11 (DIN 1.4948) für den Temperaturbereich 450–650 °C

Relaxation Behaviour of the Austenitic Stainless Steel X6 CrNi 18 11 (DIN 1.4948) in the Temperature Range 450 °C to 650 °C Based upon a set of actual data from relaxation tests after tensile loading in the temperature range 450–650 °C and with test times up to 100 h, an average stress vs. time relation for relaxation behaviour is derived. The actual dataset at the temperature of 550 °C is compared with the average relation. Relaxation behaviour is numerically computed from creep data of X6 CrNi 18 11 using different hardening theories and compared with the average relation derived from actual data.