Faserverbundwerkstoffe aus nachwachsenden Rohstoffen für den ökologischen Leichtbau

Fiber composites of raw renewable materials for the ecological lightweight design Due to their low density natural fibers have the potential to be outstanding reinforcements in lightweight structures. Since most natural fibers are hollow they also bear great potentials in offering an increased bending resistance and buckling strength. By imbedding natural fibers in organic polymers instead of in conventional petroleumbased polymers a unique completely renewable and if wanted biodegradable composite can be created. Structural components made up of this new composite material cannot only be recycled or burned (in this case even CO₂-neutral), but also be reintegrated in the cycle of natural decomposition. Presently e.g. car door linings or instrument panels have no supporting function in the car structure. In the future generation of cars weight reduction can be achieved giving these elements reinforcing functions by integrating hollow natural fibers aligned in the main loading directions. Furthermore critical regions in therms of stiffness and strength where loads are applied, like e.g. fastenings for side airbags, can be realised in the the same material without addition of metals. This can also be achieved for any other application. In this paper the potential of hallow natural fibers for reinforcements of lightweight structures, the renewable and (if wanted) biodegradable composites and their application in technical constructions will be discussed.     

Membrantechnologien für Vakuumpumpen

Diaphragm Technologies for Vacuum Pumps Diaphragm vacuum pumps are used in chemistry and as roughing pumps for high vacuum systems. Both planar diaphragms and moulded (also as »structured«) diaphragms are common. Long term tests confirmed that after some hundred hours of operation the ultimate vacuum of pumps with moulded diaphragms deteriorates due to fatigue and abrasion of the elastomer. In addition the pumping speed curve of moulded diaphragms is unfavourable for practical applications. Planar diaphragm pumps show a superior pumping speed curve and — depending on manufacturing quality — a stable performance over the whole lifetime in excess of 10,000 hours.     

Vakuumpumpen für das Chemielabor

The choice of a vacuum pump for the chemical laboratory depends more and more on economical and ecological qualifications. The water jet pump, widespread because of its simple and robust design, can satisfactorily fulfil these qualifications only in a few applications. Rotary vane and diaphragm vacuum pumps are of much more complicated design; the most outstanding assets, however, are that they work without contamination of water; further, they provide a large pumping speed also at low suction pressures.     

Betriebsmittel für mechanische Vakuumpumpen in der chemischen und der verwandten Industrie

All vacuumpummps which use a liquid as a sealing-agent have to take care of their specific demands. In this paper liquid-ring-vacuum-pumps will be short mentioned, because the user is familiar with this pumps and alternative fluids. Using other fluids in other mecanical vacuumpumps are not in operation in the field of the various applications frequently. You will find some ideas for using other fluids which are possibly used in rotary-vane vacuum-pumps to find more consideration in the future.     

Chancen und Hemmnisse für den Metallschaumeinsatz

Chances and inhibitions for the use of metal foam Materials represent more and more the initial key to market success. New developments in material research produce frequently innovative product designs. Metal foam is such an material innovation. It's been characterized by disintegrating solid structures into cellular structures. Metal foam combines excellent properties such as mass‐rigidness‐relation, vibration‐ and acoustic damping, crash‐absorption and thermal insulation effects. Despite its characteristics there is not a single application known in mass production. To investigate its reasons was the purpose of a 1999 initiated opinion poll by the Fraunhofer‐Institute in Chemnitz.     

Sicherheitnorm DIN EN 1012 – 2 für Vakuumpumpen und VBG 16

The European Standard EN 1012 – 2 Compressors and vacuum pumps – safety requirements is established in March 1996. The English text will be published in 1997. This standard is deduced from the ?Mashinery directive”? which has the state of a law in all EC member states and superseeds all so far existing national standards on this subject. In Germany for vacuum pumps it is the ?Unfallverhütungsvorschrift für Verdichter”? (compressors and vacuum pumps) VBG 16, which now is partially replaced by the new standard EN 1012. In the following the contents and the mode of employment of the new standard is discussed.     

Selbsttrocknende Membran‐ Vakuumpumpen für feuchte Gase

Diaphragm vacuum pumps have proved their superiority as dry‐running systems over other types of vacuum pumps in many applications, and in particular in the medical, analysis, and process engineering sectors, as well as in the chemical industry. These pumps deliver the media without any contamination of content, have a high gas tightness, and can be designed as chemically resistant with regard to those parts which come in contact with the media. Although they are in principle relatively insensitive towards condensates which may be formed or conveyed with the media, liquids in the vapor or gas flow may be the cause for the prolongation of a vacuum process, which can be considerable and is certainly undesirable. This applies in particular to applications involving multi‐user vacuum systems in chemical laboratories, which under certain circumstances may contain very substantial volumes of condensates, and to the use of pumps in steam sterilizers (autoclaves) and vacuum drying cabinets. These examples of applications will be considered in greater detail hereinafter. The condensates which occur in the pump head of a diaphragm vacuum pump cause interference in that — due to re‐evaporation during the suction cycle — they incur a substantial reduction in the usable suction capacity of the pump. This problem can be resolved by means of a drying system for diaphragm vac uum pump heads. The drying system makes use in this case of the pressure differential which pertains between the pump chamber and the atmosphere outside the pump. The function of the drying system can be described as follows: A solenoid valve vents the pump head in a cyclic manner, with the result that liquid in the pump head will be blown out, while the process vacuum in the process engineering system will continue to be maintained. Diaphragm vacuum pumps equipped with this drying system have provided excellent results, for example in the chem ical laboratory, both in individual diaphragm vacuum pumps as well as in multi‐user vacuum systems. Extremely good experience has also been gained in the evacuation of sterilizer autoclaves and vacuum drying cabinets with the use of diaphragm vacuum pumps fitted with the drying system. When using the drying system on steam sterilizer autoclaves, another favorable effect is also encountered: The vapor fraction in the pumping medium is cooled in the diaphragm pump head to below the evaporation or boiling temperature, with the result that the vapour condenses. This reduces its volume to a fraction of the initial value, which is the equivalent of an additional suction capacity, in the same manner as with a condenser. The condensate which occurs with this process is blown out of the pump heads by the drying system, and, as a result, can no longer cause interference due to re‐evaporation.     

Völlig ölfreie neue Vorvakuumpumpe für saubere Anwendungen

Totally oil-free vacuum pumps have been gaining popularity for applications where clean forevacuum is needed, or clean gases are being pumped. The trend for these simple applications has been to substitute the complicated and expensive process pumps used in the production of semiconductors with simpler alternatives. In order to produce such a cost effective oil-free vacuum pump, the well known reliable and robust piston principle has been adapted as a vacuum pump. The resulting product is made up of four stages of compression arranged in series producing an ultimate pressure of 3 ? 4 × 10^?2 mbar. All compression spaces are totally dry as is the crank case. For additional cleanliness the grease lubricated bearings situated in the crank case are separately sealed. The special valve geometry, and the use of new low coefficient of friction sliding materials, combine to produce a very robust and low maintenance pump. The new pump is capable of surviving operational accidents such as the ingestion of broken wafers or liquid water. Applications for this new pump include load locks, analytical instruments, and research.     

Gefüge und magnetische Eigenschaften von Chromgusseisen für Mahlkugeln

Microstructure and magnetic properties of white cast irons for grinding balls Many types of cast ferrous alloys are used for applications in the grinding, crushing, mineral‐handling and earthmoving industries. The finish grinding process for cement materials uses ball mills with differently sized grinding balls. This work deals with grinding balls of high chromium white cast irons with various chemical composition. Using certains thermal treatments, the influence of parameters of microstructure on abrasive and impact wear resistance has been studied. A special test system has been adapted for the assessment of the impact properties of these alloys. Examination of the carbides were performed using a transmission electron microscope. Additional microstructural examinations were made using the Scanning electron microscope. For a nondestructive inspection of the grinding balls, the possibilities of using the magnetic characteristics for determining the structural state and mechanical properties of white cast irons are analyzed. The results showed that the hardness and the dynamic fracture toughness are important for the combined impact‐abrasion resistance. It has been established that the microstructure has a decisive influence on the magnetical properties of white cast irons.     

Eigenschaften verschiedener Kontaktwerkstoffe für Schaltgeräte der elektrischen Energietechnik und deren Gefügeänderungen durch Lichtbogenbelastung

Properties of Different Contact Materials for Electrical Switchgear and Changes in Structure due to Arcing . Due to arcing during switching operations the microstructure of the material below the contact surface is converted. After the contacts have been used in switching their properties are determined to a great extent by the contact microstructure so formed. By means of a test switching apparatus the contact properties of the materials pure copper and pure silver produced by melting and of AgNi 10, W Ag 35 NiCuT, AgCdO 12 and AgC 3 produced by powder metallurgy were investigated during making operations and alternating making and breaking. Microsections from the used contacts were prepared perpendicular to the contact surface to evaluate the contact microstructure. Considerable differences occur in the contact microstructure depending on the type of material and switching. The contact properties welding force, contact erosion and contact resistance are affected so much by the breaking operation that it can result in a reversal of the tables of materials. In selecting a contact material with a test switching apparatus for use in a specific type of switchgear the contact properties must therefore be acquired simultaneously as a measurement series during test conditions related to the application.     

Entwicklung verbesserter Bleiwerkstoffe für den Chemie-Apparatebau,III: Mechanische Eigenschaften

Improvements in lead alloys for chemical plants, III: Mechanical properties The hardness of copper-alloyed rolled lead for chemical plants is increased by further alloying additions. The hardness of the finegrained lead alloy PbCu0.04Sn0.05Pd0.03Se0.02, which is optimum as regards processability, fine-grained structure, structural stability, and corrosion resistance, lies between that of copper lead DIN 1719 and antimonial lead containing 4% Sb. The yield point (0.2% yield strength) and tensile strength of the tested rolled lead materials increase within a certain range in a linear proportion to the hardness. This also applies to the fatigue strength. The creep strength (1% time yield limit and long-time rupture strength) likewise increases with growing hardness; this dependency diminishes, however, with rising temperature and becomes insignificant at 110°C. The improvements in mechanical properties of copper-alloyed lead to be achieved by small additions of silver (up to 0.01%) are thoroughly discussed.     

Technologische Eigenschaften warmgewalzter Bleche großer Formate aus Titan für den Anlagenbau

Mechanical Properties of Hot Rolled Plates of Large Size for Plant Engineering Large size plates of commercially pure titanium grade 1, 2 and 3 according to DIN 3.7025, 3.7035 and 3.7055 up to 3500 mm width and a maximum length of 10000 mm with a thickness of 7 and 30 mm have been tested. They fullfill the acceptance specifications for hot rolled plates of conventional size regarding flatness, thickness tolerances and mechanical properties at room temperature. The availability of plates with a very high flatness creates the basis for large sizes explosion cladding with commercially pure titanium as surface layer material. Additional investigations between ? 196°C and + 400°C for the mechanical properties and notched impact strength of plates and weldments as well as fatigue strength at room temperature show, independent of the rolling direction, the possible influence of grain size and interstitials like oxygen and hydrogen as well as of the iron content on the properties. The notched impact strength has a maximum at 100°C without a steep drope at lower temperatures. The decrease of tensile strength and proof stress with increasing temperature show a retarding effect at 150°C. The elongation reaches a maximum at 200°C, combined with a low ratio of yield strength to tensile strength.     

Mechatronische Lösungen für trockenlaufende Vakuumpumpen. Mechatronic solutions for dry vacuum pumps

Mechatronik is a combination from Mechanics and electronic and can be defined as a special view and method of engineering. The main difference compared with the traditional way of mechanical and electronic design is the other way of specification and engineering. Interfaces and specification are focused on different blocks and modules on a functional way, independent how it is realized. The results are not only new innovative solutions with better usage of the modern control possibilities. Also for the interfacing, installation and support this way of engineering give many advantages and possibilities for cost reduction. This paper shows on dry vacuum pumps and systems in the chemical and pharmaceutical industry the actual solutions which are available to use these advantages.     

Aufbau und Eigenschaften glasfaserverstärkter Eisenverbundwerkstoffe

Properties and Microstructure of Iron-Glassfiber Composites It is possible to produce powdermetallurgically glasfibre reinforced iron composites after high deformation by extrusion. These materials represent some interesting technological aspects because an anomalous increasing in tensile strength and other mechanical properties can be found, although the Young's-Modulus of the additive is lower than of the matrix. On the other hand electrical conductivity and Young's Modulus of the composites show a linear decreasing with the volume fraction of the second phase. This behaviour is reasoned in the fibre structure of the composites. Other physical properties such as thermal conductivity or the internal friction show an anomalous behaviour because of an excursive phononscattering at the interphases, which the curled microstructure possess in multiple forms.     

Sinterwerkstoffe für elektrische Kontaktstücke der Energietechnik und ihre Eigenschaften

Sintered Materials for Electric Contacts in Power Engineering and their Properties . In the field of electric contacts the task of material development lies in optimating of contact properties e. g. weld strength, erosion and contact resistance. Included is a survey of the systems of metal-metal, metal-metal compound and metal-metaloid including examples for base metals and additives. Knowledge of weld strength and erosion by arcing are necessary besides physical properties and structure for selecting contact materials. The properties mentioned have been measured by WATE (welding-arc erosion-test-equipment). The values of the weld strength are presented as cumulative frequency plottings. Joining-technique of contact and supporting metal is of special importance. A reliable connection is obtained by two-layer-contacts. Changes of structure caused by arcing are described; for example contacts from AgNi40, WCu30 and AgCdO12. Both, construction and modern contact materials have helped to increase the capacity of contactors and switches as well as the reliability.     

Vakuumsystem für den Hochenthalpie-Windkanal

The Institute for Experimental Fluid Mechanics of the DLR in Göttingen has been charged with the task of manufacturing a wind tunnel (unique in Europe) for the investigation of Re-entry Aerodynamics with High Enthalpy Streaming for the simulation of real gas effects.