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Organisationseinheit der BAM
Liquid adsorption chromatography at critical conditions (LACCC) in normal and in reversed-phase modes provides independent information on the molar mass distributions of both blocks of poly(methyl methacrylate)-block-poly(tert-butyl methacrylate), even if no information about the precursor is available. In addition, the amount of unreacted precursor can be determined, even if its molar mass is comparable to that of the total block copolymer. The reversal of elution order by changing of stationary and mobile phases makes it possible to independently characterize each block in the SEC mode of the LACCC system. Thus, complete structural information is obtained even without using two-dimensional chromatographic techniques.
Laser beam oscillation, applied one- or two-dimensional to the actual welding process, influences the welding process in terms of compensation of tolerances and reduction of process emissions like spatter and melt ejections that occur in industrial applications, such as in body-in-white manufacturing. If the welding process could be adapted to these tolerances by the momentarily demanded melt pool width to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing, laser welding would become more robust. However, beam oscillation results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 μm laser spot show that oscillation strategies which are adjusted to the joining situation can bridge gaps to approximately 0.6 mm at metal sheet thickness of 0.8 mm. However, the complex behaviour of the melt pool has to be considered to generate proper welding results. This work puts emphasis on showing aspects of beam oscillation in fillet welding in lap joints.
In todays automotive frame-and-body construction, laser welds are typically carried out as square butt welds in lap joints. These welds are increasingly produced by remote laser welding optics with working distances of 500 mm and more. This enables simple path programming because clamping devices are traversed over and therefore low cycle times with improved productivity is achieved. However, workpiece tolerances lead to part displacements and varying joint positions over time. These displacements have to be acted against by appropriate flange length that contain for positioning deviations. Using this concept, aspired light-weight optimisations, e.g. reducing flange length, are difficult to achieve. By using seam tracking sensors, part tolerances are automatically detected and counteracted for. In addition, joint edge detection allows constructive changes on the type of weld. Fillet welds reduce flange lengths', improve force flow and open up possibilities for visual quality monitoring. Apart from that, vertical displacements in the form of height tolerances still occur. This needs consideration by adapting the set of welding parameter to the current welding situation. In this respect, one main welding parameter is the lateral beam offset to the upper sheet. Since body-in-white welding applications mainly comprise of zinc-coated steel sheets, special requirements for the welding process are given. Especially zero-gap-welding and welding of joints with gaps larger than 0.2 mm are critical. Using a laser beam oscillation process can stabilise these situations. Approaches to finding parameter sets are presented in this paper.
Laser beam oscillation opens up new possibilities of influencing the welding process in terms of compensation of tolerances and reduction of process emissions that occur in industrial applications, such as in body-in-white manufacturing. The approaches are to adapt the melt pool width in order to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing. Welding results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 µm laser spot show that oscillation strategies, which are adjusted to the joining situation improve welding result for zero-gap welding as well as for bridging gaps to approximately 0.8 mm. However, a complex set of parameters has to be considered in order to generate proper welding results. This work puts emphasize on introducing them.
Heterogene und feinkörnige Bauabfälle aus Mauerwerkbruch lassen sich heute nur auf einem sehr geringen Qualitätsniveau verwerten. Um diese Situation zu überwinden, wurde das Material als Rohstoff für die Herstellung von leichten Gesteinskörnungen verwendet, die ähnlich wie Blähtone und Blähschiefer in einem thermischen Prozess erzeugt werden. Auf der Grundlage einer Literaturübersicht wurde zunächst die grundsätzliche Eignung von Mauerwerkbruch bewertet. Es folgten experimentelle Untersuchungen, in welchen nachgewiesen werden konnte, dass Leichtgranulate mit definierten, einstellbaren Eigenschaften aus Mauerwerkbruch herstellbar sind. Sie sind in ihren Eigenschaften den leichten Gesteinskörnungen aus natürlichen Rohstoffen mindestens ebenbürtig. -----------------------------------------------------
At present heterogeneous and fine-grained masonry rubble is recycled at a very low level. To overcome this situation the material is used as feedstock for the generation of lightweight aggregates, produced by a thermal process similar to the manufacturing of expanded clays and shales. On the basis of a literature review the suitability of masonry rubble as raw material is evaluated generally. Then materials from different recycling plants were experimentally tested. The results show, that expanded granules with defined, adjustable properties can be produced from masonry rubble. The properties of these secondary lightweight aggregates are at least equivalent to the properties of the known expanded clay aggregates.
Neue leichte Gesteinskörnungen werden durch rohstoffliches Recycling aus heterogenem und feinkörnigem Mauerwerkbruch hergestellt. Die Erprobung dieser Aufbaukörnungen im Leichtbeton liefert Aussagen zu ihrer Qualität und Eignung. Nach einer kurzen Charakterisierung der für die Betonherstellung ausgewählten Aufbaukörnungen werden die entworfene Betonrezeptur vorgestellt und einige Ergebnisse der Festbetonuntersuchungen diskutiert.----------------------------------------------------------------------------------------------------------
New lightweight aggregates are produced by feedstock recycling from heterogeneous and fine-grained masonry rubble. Testing of these tailor-made expanded aggregates in lightweight concrete provides information about their quality and performance. Following a brief characterization of the tailor-made expanded aggregates used in concrete production, the concrete mix design is presented and some results of the tests of hardened concrete are discussed.
Die Ressourcenverknappung und steigende Preise rücken nachhaltiges Wirtschaften und die Wiederverwertung von Abfällen in den Blickpunkt der Forschung. Bauabfälle sind in Deutschland – mit 72,4 Mio.t im Jahr 2004 – der größte Abfallstrom. Es wird ein Überblick über den Stand der Technik zur Aufarbeitung und Verwertung von Bauabfällen gegeben und die Anforderungen an Bauabfälle, die als Sekundärrohstoff eingesetzt werden sollen, diskutiert. Die Forschung im Baustoffrecycling bezieht sich sowohl auf neue Aufbereitungstechniken als auch auf die Charakterisierung der Recyclingmaterialien sowie auf deren Einfluss auf die Betonqualität. Die Eignung und Verwertung von Bauabfällen als Sekundärrohstoffe für Baustoffe wird anhand ihrer chemischen Zusammensetzungen mit Hilfe von ternären Diagrammen diskutiert.----------------------------------------------------------------------
An overview about quantity of construction and demolition waste (CDW) and a state of the art of the reuse is given. The technology is described, which is applied for the processing of CDW in a stationary plant. The requirements on recycled aggregates, which shall be used in road construction or in manufacturing of concrete, can be divided in such related to the material and physical properties and such related to the environmental properties. The rules give guidance on the composition with the aim of excluding the constituents with unfavourable features. The environmental standards which yet in discussion are give threshold of the leachable components in recycled aggregates. The material potential of building waste is discussed. Information on the chemical composition of recycled materials is compared with the composition of pure materials. With the aid of ternary charts such building materials are identified, in which the recycled materials can be used as recycled feedstock.