620 Ingenieurwissenschaften und Maschinenbau
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In dieser Studie wird die Umsetzbarkeit von solarthermischen Großanlagen in der südafrikanischen Getränkeindustrie mit üblicherweise großen Produktionsanlagen in den Provinzen Gauteng und Western Cape untersucht. Für die technischökonomische Bewertung werden verschiedene kommerziell verfügbare Kollektortypen gegenübergestellt, charakteristische Energiebedarfsprofile für „ready-to-drink“ Getränke definiert und Simulationen in Polysun für verschiedene Konfigurationen, mit und ohne Speicher, durchgeführt. Es zeigt sich, dass Parabolrinnenkollektoren in den wichtigsten Wirtschaftszentren Südafrikas rentabel sein können, um Gas, Schweröl, Diesel und sogar Kohle zu ersetzen, Dieser Ansatz könnte breiter auf den Lebensmittel- und Getränkesektor angewendet werden, wo die meisten Dampfheizsysteme zu finden sind.
Oleamide is used as a lubricant in the manufacturing and application of polypropylene (PP) medical devices. Samples of PP were prepared with 0, 1500, and 15 000 ppm oleamide content as lubricant. The samples were either left non-sterile, sterilized with ethylene oxide (ETO), γ-radiation (γ) or autoclaved (A) and stored for up to 4 weeks. To determine the oleamide bulk-to-surface distribution depending on sterilization method and storage time an extraction method and a washing technique were applied. The oleamide content was determined by gas chromatography (GC-FID) and compared with the coefficient of friction (COF). The COF dependent on the measured lubricant content at the surface. The content of lubricant on the surface depends on the type of sterilization: ETO increased the lubricant content to some extent, γ-sterilization and autoclaving reduced it. After storage, no migration of the lubricant to the surface could be detected.
Bamboo is an environmentally friendly alternative to conventional materials in mechanical engineering such as steel or aluminium. Bamboo is the fastest growing plant in the world. Instead of releasing CO2 during the manufacturing process, bamboo absorbs CO2 as it grows.
In addition to the sustainability aspect, bamboo tubes also offer excellent properties as a lightweight construction material, which have been optimised through evolution. Bamboo tubes have high strength and stiffness at low weight when used as tension-compression bars or bending beams. Bamboo has strong, high-density fibres at the boundary area, where bending stresses are greatest. Towards the inside, where the stresses are lower, the bamboo becomes porous to optimise weight. This, together with knots arranged in regular intervals, counteracts buckling.
In mobile applications such as cars and bicycles, lightweight construction is sought for energy efficiency reasons. Because of its excellent lightweight properties, the project investigated whether bamboo could be used in mobile, automotive or agricultural engineering. For example, a bamboo bicycle frame has been developed with the aim to be as light as possible. There are bamboo bicycles on the market, but they can only be made one at a time by hand. The bamboo tubes are joined together and functional elements such as the bottom bracket and headset are integrated by wrapping them in resin-impregnated natural or carbon fibres. This makes the joints very heavy. A different approach is taken here: the bamboo tubes are drilled out slightly to achieve a defined internal diameter, and then short aluminium tubes are glued into the bamboo canes from the inside. To prevent the cane from breaking in the circumferential direction, i.e. perpendicular to the fibre direction, the bamboo tubes are wrapped in a thin layer of natural or carbon fibre impregnated with synthetic resin. The aluminium tubes and functional elements are welded or soldered together beforehand.
The design of the bicycle frame, i.e. the dimensioning of the bamboo tubes and joints, was based on extensive bending and tensile tests to determine the strength properties of the natural material bamboo. The bonding between the bamboo cane and the aluminium tube was also investigated experimentally. Finally, several prototype bicycle frames were made and tested for durability according to DIN-EN-14764. The frames passed the tests.
The result is a bamboo bicycle that is manufactured with standardised connectors and joints. The assembly concept developed allows both fully automated and semi-automated series production of bamboo bicycles.
Currently, soil nutrient analysis involves two separate processes for soil sampling and nutrient analysis: 1. field soil sampling and 2. laboratory analysis. These two - separate - main work processes are combined and conceptualised for a mobile field laboratory so that soil sampling and analysis can be carried out simultaneously in the field. The module-based field laboratory "soil2data" can carry out these two main work processes in parallel and consists of 5 different task-specific modules that build on each other: app2field, field2soil, app2liquid, liquid2data and data2app. The individual modules were designed and built for the sub-process steps and adapted to the special features of the mobile field laboratory "soil2data". The biggest advantage is that the analysis results are available immediately, and a fertiliser recommendation can be generated instantly. For further analyses, the results are stored in the data cloud. The soil material remains in the field. In the ongoing project "Prototypes4soil2data", the mobile field laboratory soil2data is being further developed into a prototype with a modular structure.
Lab@Home ist eine Open-Source-Experimentierplattform für Laborpraktika in der Regelungstechnik, der Automationstechnik und der Informatik. Sie besteht aus einer elektronisch-mechanischen Bau-gruppe, einer webbasierten Experimentiersoftware sowie der Dokumentation verschiedener differen-zierbarer Lernmodule. Die Bauteile für eine Einheit kosten unter 30€ und können innerhalb von 30min zusammengebaut werden. Für die Durchführung der Experimente stehen eine webbasierte Be-nutzerschnittstelle (WebApp) und eine Schnittstelle zu WinFACT Boris zur Verfügung. Lab@Home wird seit mehreren Semestern in verschiedenen Lehrveranstaltungen erfolgreich eingesetzt.
Innerhalb eines Forschungsprojektes wurde ein Energiesystemoptimierungsmodell entwickelt, das mögliche Geschäftsmodelle als Weiterbetriebsoptionen für Biogasanlagen betrachtet. Insbesondere der Einfluss von fluktuierenden Strommarktpreisen und variierenden Treibhausgasquoten soll kritisch im innerdeutschen Kontext beleuchtet werden.
Reibermüdung ist ein Phänomen, welches an den Kontakträndern von in Berührung ste-henden, kraftübertragenden Bauteilen beobachtet werden kann. Typische Maschinenele-mente, die in diesem Mode versagen können, sind z. B. die Schwalbenschwanzverbindung sowie ihre Ableger, die mehrzahnigen Tannenbaumfixierungen. In der Literatur beschrie-bene Untersuchungen weisen für Flachproben mit Reibbrücken ein Lebensdauerverhalten mit einem lokalen Minimum über der Anpresskraft der Reibbrücken aus. Die vorliegende Arbeit untersucht mithilfe des Sines-Ermüdungskriteriums, kombiniert mit Grenzwerten gemäß FKM-Richtlinie, ob ein solches Verhalten auch für die Schwalbenschwanzverbin-dung zutrifft. Im Gegensatz zur Reibbrückenanordnung mit separater Einleitung von kon-stanter Pressung und Längslastamplitude fluktuieren bei der Schwalbenschwanzverbin-dung die Anpresskraft und Zugkraft mit der einzigen am Hals eingeleiteten Last.
A systematic study was performed to understand the effects of the devulcanizing agent dibenzamido diphenyl disulfide (DBD) on the vulcanization and devulcanization process of a sulfur-cured ethylene-propylene-diene monomer (EPDM) rubber. The influence of DBD on vulcanization was investigated by mixing DBD with virgin rubber and curative system. The devulcanization of rubber waste was achieved with varying amounts of DBD ranging from 0.4 to 13.8 wt% and temperatures from 150 to 200°C. The quality of vulcanizates and devulcanizates was evaluated by rheometer tests, temperature scanning stress relaxation measurements, and analysis of mechanical properties. During vulcanization, DBD acts as an accelerator in the presence of sulfur. When accelerators are added, the scorch time increases, and the cure rate decreases. Thus, DBD acts as a retarder. In the presence of activators, DBD leads to a significant reduction of crosslink density. This results in composites with high elongation at break and poor compression set values. The efficiency of the devulcanization of rubber waste depends strongly on DBD concentration and temperature. The monosulfidic crosslinks are cleaved by low concentrations of DBD, while polysulfidic crosslinks require higher concentrations. These results show that DBD is effective as a devulcanizing agent and degrades the network below 200°C.
In this experimental work, the quasi static and fatigue properties of a 40 wt.% long carbon fiber reinforced partially aromatic polyamide (Grivory GCL-4H) were investigated. For this purpose, microstructural parameter variations in the form of different thicknesses and different removal directions from injectionmolded plates were evaluated. Mechanical properties decreased by increasing misalignment away from the melt flow direction. By changing the specimen thickness, no change in the general fiber distribution pattern transversal and normal to the axis of melt flow was observed. It has shown that with increasing specimen thickness the quasi static properties along the melt flow direction decreased and vice versa resulting in superior properties normal to the melt flow axis. At around 5 mm, an intersection suggests quasi-isotropic behavior. In addition, the fatigue strength of the material was significantly higher in the flow direction than normal to the flow direction. No change in fatigue life was observed while changing specimen thickness. The Basquin equation seems to describe the effect of stress amplitude on the fatigue strength of this composite. Scanning electron microscopy was used to investigate fracture surfaces of tested specimens. Results show that mechanical properties and morphological structures depend highly on fiber orientation.