Sicherer und wirtschaftlicher Betrieb von Kraftwerken – Ergebnis der Forschung im Bereich Werkstoffe,Auslegung und Instandhaltung

Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available.     

Einsatz moderner Informationstechnik im militärischen Bereich: Für den Verteidiger notwendig und verantwortbar

Zusammenfassung Nach Pädagogen, Ärzten etc. haben sich nun auch Informatiker für den Frieden organisiert. So sehr sich der Verfasser mit den Zielen von Friedensinitiativen identifizieren kann, so sieht er doch die Gefahr, daß diese Bemühungen insgesamt eher destabilisierend und damit kontraproduktiv wirken. Bevor im folgenden Beitrag dieser Gedankengang weiter ausgeführt wird, soll zunächst versucht werden, die Bereiche darzustellen, in denen bislang und in absehbarer Zukunft Rechensysteme in modern ausgerüsteten Streitkräften eingesetzt werden, wobei besonders auf die Situation in Mitteleuropa und speziell auf die Bundeswehr eingegangen wird. Es wird aufgezeigt, daß gerade der Verteidiger auf moderne Führungs- und Aufklärungssysteme angewiesen ist, insbesondere in der kritischen Anfangsphase eines Konflikts, und daß die Vertreter alternativer Verteidigungsstrukturen, die den Schwerpunkt auf defensiv ausgerüstete Verbände mit struktureller Nichtangriffsfähigkeit legen, wie auch offizielle Programme der NATO zur Verbesserung der konventionellen Verteidigungsfähigkeit auf moderne Technologie setzen. In diesem Zusammenhang wird ein Forschungsprojekt vorgestellt, das zum Ziel hat, die Wirksamkeit derartiger reaktiver, rüstungskontrollfreundlicher Verteidigungs- und Bewaffnungsstrukturen sowie moderner Technologie im Gefecht der verbundenen Waffen zu untersuchen. Entsprechend der Themenstellung dieses Sonderheftes soll schließlich auch auf moralisch-ethische Aspekte des Einsatzes moderner Informationstechnik für die Verteidigungsplanung eingegangen werden. Dies geschieht in der Form von Thesen, um die Aussagen als persönliche Meinung des Verfassers besonders zu kennzeichnen.     

Photoelectric properties of the photoconducting film composites based on ferrocenyl‐ and carbazolyl‐containing oligomer doped with polymethine dye

New photosensitive polymeric film composites based on oligomer containing ferrocenyl and carbazolyl fragments doped with symmetric polymethine dye are synthesized. Their photoelectric properties are investigated. Photovoltaic properties of these composites are detected. The mechanisms and peculiarities of the photovoltaic and photodielectric effects are discussed.     

Ultraschallbasierte in situ Vorspannkraftermittlung an Schrauben ohne Referenzmessung im nicht verspannten Zustand durch Kombination von Longitudinal- und Transversalwellen

Ultrasonic based bolt preload evaluation is commonly performed using the mono-wave method. This method works by measuring the time of flight of longitudinal waves. Here, a reference measurement in the unloaded condition is necessary for each bolt. In this publication the longitudinal wave is complemented by another type of ultrasonic wave - the transverse wave. This method does not require a reference measurement in the unloaded condition for each bolt. Moreover, an analytic method for determining the bolt-specific K-value is introduced, which is needed for the ultrasonic bolt preload determination. The analytically calculated K-values are compared with experimental K-values from tensile tests. The influence of material, bolt property class and surface protection system were determined with cylindrical specimens. In component tests, the bolt preload was evaluated using the bi-wave method, a possible influence of the bolt assembly method was investigated and the results were interpreted regarding their accuracy.     

Design of a Medical Non‐Linear Drilling Device: The Influence of Twist and Wear on the Fatigue Behaviour of NiTi Wires Subjected to Bending Rotation

This paper considers fundamental and experimental aspects associated with the engineering design of a medical, non‐linear drilling device which exploits shape memory pseudoelasticity of NiTi wires. For this application it is important that the NiTi wires have a good fatigue resistance. This is why the present authors have previously determined the influence of various parameters on cyclic life, crack growth and stress state of pseudoelastic wires subjected to bending rotation fatigue. The actual drilling device has to withstand twist in addition to bending rotation because the free rotation is constrained by friction between the drill head and the bone material. In addition, friction between the wire and a NiTi guiding tube results in wear and this may well promote fatigue crack nucleation. In this paper, we explain the function of the medical drill. We then report results on the effect of the additional parameters (1) twist and (2) wear on the fatigue life of thin pseudoelastic NiTi wires. We finally discuss the implications of our experimental results for the design process of the medical drilling device.     

Werkstoffkennwerte für die Lebensdauerberechnung von Strukturen aus Stahlfeinblechen für den Automobilbau

Materials Data for Fatigue Life Calculation of Steel Sheet Structures for Automotive Engineering Within a joint project of the steel and automotive industry 17 steel sheet materials for automotive engineering in various delivery and forming conditions at temperatures of –40 °C, 22 °C and 100 °C were investigated. In the course of 37 test series strain controlled fatigue curves to crack initiation and stress‐strain‐curves under monotonic and cyclic loading were determined. All experimental data, hysteresis loops and determined cyclic properties are available in a database. A correlation between the mechanical properties from tensile tests and the properties from strain controlled cyclic experiments seems to be possible.     

Investigations of electrochemical double layer capacitor (EDLC) materials – a comparison of test methods

A comparison between various methods for determining the capacitance and resistance of electrochemical double layer capacitors (EDLC) with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge‐discharge methods and cell voltage jump experiments are presented. Therefore, a commercially available electrochemical double layer capacitor was used. For the validation of the screw cell measurements the electrode foils were isolated and extracted from the commercial capacitor. The results support the adequacy of the screw cell tests for electrode materials on a laboratory scale. The comparison of methods shows in part strong differences. The reasons will therefore be discussed. Consequently, the determination of specific values requires methods which respect the influence of the actual tests or measurement frequency and exhibit the importance of an internationally accepted specification for electrochemical double layer capacitors material investigation.     

Wachstumsmessungen von Kristallen in sauberen und verunreinigten Lösungen: Einzelkristall vs. Kollektiv

Information about crystal growth rates and the influence of impurities are essential for the design of industrial crystallization processes. Here, the influence of trivalent metal ions Fe³⁺ in solution and adsorbed in the crystal on the growth and dissolution rate is investigated. The results clearly show kinetic and thermodynamic effects caused by impurities which have to be taken into account in the equipment design. Furthermore, effects of growth rate dispersion must be excluded by investigation of crystal collectives. Additionally, the crystal growth data should be obtained from real starting solutions.