Europäische Normen in der Lecksuchtechnik

European Standards with regard to Leak Detection Technologies The following article gives a review on the European standards (EN) with regard to leak detection technologies. On the one hand, the contents of these standards are summarized with regard to test methods and test equipment. On the other hand, the specifications are described which have to be met in Europe by the personnel which is consigned to perform leak detection.     

Teilautomatisiertes preforming zur Qualitätssicherung und Verkürzung von Fertigungszeiten bei der Herstellung von Rotorblättern von Windenergieanlagen

Quality management and reduction of processing time through automised preforming in the rotorblade manufacturing for wind turbines Rotor blades of wind turbines are mainly manufactured from fibre reinforced plastics. These materials show an excellent performance concering the ratio of stiffness and weight. Basically the composite material of rotor blades is made out of glass fibres and thermosetting material. But growing technological and economical requirements to rotor blades by off‐shore‐application, in particular through increasing rotor blade diameter, have to meet successful. Although reduction of processing time and increased quality of rotor blades play a major role. To achieve the increasing requirements of the rotor blade manufacturing the Bremen Institute for Engineering Design and the rotor blade manufacturer Abeking & Rasmussen Rotec GmbH are working together on the handling and manufacturing of textile preforms. Preforms are made out of stacked and bonded dry textile layers and deposited in the mould as one textile part. Preforming allows the parallel processing of some manufacturing steps. This shows great advantages in the production of fibre reinforced plastics because of the long curing time of the resin component. This parallel processing is required to reach the aim of decreased overall cycle time. This essay is focussing on the handling of textiles and the textile preforming. Summarised aspects of quality management and economics in textile preforming will be discussed with the aim of automising the preforming process.     

Beiträge zur Untersuchung der Korrosion An Modellwerkzeugstählen für kunststoffverarbeitende Maschinen

Contributions to the Study of the Corrosion on Models of the Alloy Steels for Plastic Processing Machines The corrosion on the alloy steels 9 S 20 K and 165 X CrMoV 12 during processing of glassfiber reinforced and non-reinforced plastic melts of styrene-acrylonitrile-copolymer, polypropylene, styrene-acrylonitrile-copolymer, polypropylene, styrene-acrylonitrile-butadiene-copolymer and polycarbonate were tested. The volatile compounds evolved during injection molding were condensed and analysed by means of gas-chromatography (GC), gas-chromatography-mass-spectroscopy (GC-MS) and nuclear-magnetic-resonance (NMR). They mainly consisted of hydrocarbons and monomers form the degraded plastics. Because of the absence of water, electrochemical corrosion need not be considered. A mechanism on the basis of chemical reactions between the polymer melt and the steel surface was considered to cause corrosion. By means of scanning electron microscopy differences in the surfaces of the steels corroded with different polymer melts could be observed. Analysis of the surfaces by secundary-ion-mass-spectroscopy (SIMS) resulted in changes being specific for the polymers. On all the corroded steel surfaces high spectral carbon intensities were detected compared with non corroded ones, as well as higher intensities for the steel compounds like chromium, manganese and vanadium. Chemical reactions of these compounds with the polymer melt were considered to cause changes in the lattices of the steel resulting in a change of the properties.     

Entwicklung von Werkstoffmodellen zur Beschreibung der lokalen Eigenschaften der Wärmeeinflusszone von hochfesten Feinblechen

The analysis of the complete process chain is an important requirement in the fine sheet metal working for the improvement of strength evaluation of structures and components. Particularly at applications of high‐strength steel sheets the development of material properties as well as the production process play a decisive role, because of the complex requirement profile these steels have to satisfy. In the context of the represented research the material reactions were experimental examined on the basis of the thermal effect of different joining processes at multiphase steel. The investigations were accomplished on HCT600XD, HCT780XD, SZBS800 and LH800. Exemplarily the article discusses the procedures and the results of the research of HCT600XD and SZBS800.     

Einsatz von Vakuumpumpen bei der Herstellung von Photovoltaik‐Modulen

Use of vacuum technology in crystal pulling and lamination application in manufacturing of photovoltaic modules Dry compressing screw type vacuum pumps such as the SCREWLINE SP 630/250 are designed to reduce cost of ownership in crystal pulling plant and in lamination processes. The construction of gear house sealings, the easy maintenance of the pump on site and the use of gas ballast guarantee a very reliable performance, and long maintenance and service intervals. In the case of crystal pulling the process does not even need a dust separator at the inlet of the vacuum pump.     

Statische Vakuumentgasungsapparate bei der Herstellung und Qualitätserhöhung von Kunststoffen

Static devolatilization is a simple and older process which has been so much improved by the introduction of static mixers and by system optimization that it can fulfill all the modern demands of polymer processing, including additive mixing. Enhanced devolatilization, which continues to grow in importance, requires a high degree of efficiency – verging on the equilibrium value – in order to satisfy demands for low residual monomer values, economically and under industrial operating conditions. Contrary to expectations, this goal can be reached quite simply by the employment of static devolatilization, as it will convincingly show in this survey. Polymers with viscosities up to 20000 Pas can be discharged safely. Thanks to the substantial process improvements static devolatilization will spread increasingly to those areas where it is not yet used as standard practice.     

Dünnschichtanlagen zur Herstellung von flachen Bildschirmen

The production of flat panel displays requires thin film technologies, which are also known from microelectronics. An essential difference, however, is the substrate size. The deposition of metals, dielectrics and semiconductors is carried out by sputtering and CVD processes in large area in-line systems. Dry etching for the structuring of the substrates is realized in static, single substrate machines.     

Einsatz des Explosivschweißens zur Herstellung von Edelmetallplattierungen

Explosive Welding as a Technique for Cladding of Precious Metals The method of explosive welding and the importance of the cladding parameters are described. The “Explosive Weldability Window” is experimentally determined for the material combination AgCu 10/Fe. The behaviour of explosive claddings produced under different conditions during rolling is investigated. Best results are obtained with samples with a wavy interphase, produced under the following cladding parameters: It is shown, that in comparison with conventional methods explosive cladding has advantages both in processing and quality.     

Anwendung dilatometrischer Messungen bei der Entwicklung von Glasloten und reaktiven Metallloten zum Fügen von Hochtemperaturbrennstoffzellen

The principle of operation of solid oxide fuel cells (SOFCs) is very simple. However, the fact that very different materials are used for the individual components requires advanced thermal joining techniques to join them in a functional manner. Two very distinct designs have established themselves for the two different intended applications: decentralised power generation (stationary SOFCs) on the one hand, and power converters for vehicles (mobile SOFCs) on the other hand. As a consequence, alternative techniques for joining the individual components are also required. The principal joining process for the stationary SOFC design consists of joining individual steel plates with a glass sealant in an electrically insulating way so that they form an SOFC stack. For the mobile fuel cell design, the SOFC stack consists of individual thin steel cassettes. The window frame of the cassettes, which is made of ferritic chromium steel, is brazed to the ceramic layer of the zirconium oxide solid electrolyte using a filler metal. The material used is a silver‐based brazing filler metal which contains only small amounts of copper oxide (CuO) and titanium hydride (TiH₂) as wetting agents. Both joining processes must be applicable in normal atmospheric air, i. e. under oxidative conditions. R&D activities continue for improving the efficiency and long‐term operational stability of the technology to such an extent that SOFCs will become ready for the energy sector market. The two joining techniques described cannot yet be considered standard processes. They, too, will require continuous improvement with respect to reproducibility, endurance and strength of the joints. The Special Joining Techniques working group at Forschungszentrum Jülich uses specially modified dilatometric techniques as suitable quick replacement methods for studying and measuring the joining characteristics of the materials without having to manufacture complex and expensive SOFC stacks. The shrinkage processes in the glass sealant joints are simulated and measured in the μm range using a special dilatometer. In this way, the amount of glass sealant – which is decisive for tightness and bonding – and the process parameters can be determined in advance. With a vertical dilatometer, the melting behaviour of the reactive silver filler metals is examined with respect to melting point shift, viscosity and void ratio, and as a function of the metal additives (Al) and the process atmosphere.     

Entwicklung von Oxid – Keramik zur Anwendung als Wärmedämmschichten

Development of Oxide Ceramics for an Application as TBC The standard thermal barrier coating material yttria stabilised zirconia (YSZ) is limited in long term operation to a maximum temperature of about 1200°C. As a result further increase of the gas inlet temperature and hence the efficiency of gas turbines are hardly to achieve with YSZ coatings. In a screening procedure especially perowskite (ABO₃, A = Sr,Ba, B = Zr) and pyrochlore (A₂B₂O₇, e.g. A = La and other rare earth elements, B = e.g. Zr) materials have been identified as possible candidates for thermal barrier coatings. Basic physical properties (e.g. thermal expansion coefficient, thermal diffusivity and conductivity) of several candidates have been determined using sintered, dense samples. The possibility of optimization of the properties by using specific compositions will be discussed. From promising materials powders which are suitable for plasma‐spraying have been produced by spray‐drying. New TBC systems consisting of new materials (BaZrO₃, La₂Zr₂O₇) deposited by atmospheric plasma spraying and vacuum plasma sprayed MCrAlY bondcoats were tested in a gas burner facility. Especially La₂Zr₂O₇ coatings gave promising results. A further improvements could be achieved by the use of layered or graded coatings with a YSZ coating at the bondcoat interface and on top a layer of the new TBC material. First results of thermal cycling tests with 1250 and 1350°C surface temperature will be presented.