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Entwicklung eines digitalen Instruments zur Feststellung relevanter Kompetenzen im Maschinenbau
(2021)
Leichtbaustrukturen kommen in vielen Branchen und Bereichen zum Einsatz. Vor allem der Fahrzeugbau sowie die Luft- und Raumfahrt profitieren von dem geringen Materialeinsatz und der Einsparung in der Nutzungsphase. Neben den genannten Potenzialen bieten Leichtbaustrukturen die Möglichkeit, gezielt eine hohe Dämpfung von Vibrationen bei geringem Materialeinsatz zu kombinieren. In diesem Zusammenhang werden häufig sog. Sandwichstrukturen verwendet. Die Sandwichstrukturen bestehen in der Regel aus kraftaufnehmenden Deckschichten und weicheren Kernschichten aus einer Wabenstruktur oder Vollmaterial aus Kunststoffen. Letztere übernehmen häufig die Aufgabe der Dämpfung.
In diesem Beitrag wird die Dämpfung einer ebenen Sandwichstruktur bestehend aus einer metallischen Deckschicht und einer viskoelastischen Polymerschicht untersucht. Die Herausforderung liegt in der physikalischen Modellierung der Materialdämpfung sowie der Übertragung der experimentell gewonnenen Daten in ein Finite-Elemente Simulationsmodell. Hierzu werden bestehende Methoden der Dämpfungsidentifikation evaluiert. Anschließend wird die Struktur mithilfe einer experimentellen Schwingungsanalyse unter vorgegebenen Randbedingungen analysiert. Aus den gewonnenen Messdaten werden Parameter ermittelt, um ein frequenzabhängiges Materialmodell zu generieren. Neben dem Vergleich der experimentellen und berechneten Ergebnisse liegt der Schwerpunkt dieses Beitrags auf der Betrachtung von Unsicherheiten während des Prozesses.
Additive manufacturing processes, particularly Laser-Based Powder Bed Fusion of Metals (PBF-LB/M), enable the development of new application possibilities due to their manufacturing-specific freedom of design. These new fields of application require a high degree of component quality, especially in safety-relevant areas. This is currently ensured primarily via a considerable amount of downstream quality control. Suitable process monitoring systems promise to reduce this effort drastically. This paper introduces a novel monitoring method in order to gain process-specific thermal information during the manufacturing process. The Synchronized Path Infrared Thermography (SPIT) method is based on two synchronized galvanometer scanners allowing high-speed and high-resolution observations of the melt pool in the SWIR range. One scanner is used to steer the laser over the building platform, while the second scanner guides the field of view of an IR camera. With this setup, the melting process is observed at different laser powers, scan speeds and at different locations with respect to the laser position, in order to demonstrate the positioning accuracy of the system and to initially gain thermal process data of the melt pool and the heat-affected zone. Therefore, the SPIT system shows a speed independent overall accuracy of ±2 Pixel within the evaluated range. The system further allows detailed thermal observation of the melt pool and the surrounding heat-affected zone.
In an interdisciplinary collaboration of people from different parts of Germany working with and researching on the method "Decoding the Disciplines" (DtD), the topic "Finding Student Bottlenecks" has been investigated. In the process, the use of quality management methods from the engineering field has been evaluated in order to achieve an improved structuring of the bottleneck search not only for engineering bottlenecks but also for bottlenecks from other disciplines.
Nowadays, additive manufacturing processes are becoming more and more appealing due to their production-oriented design guidelines, especially with regard to topology optimisation and minimal downstream production depth in contrast to conventional technologies. However, a scientific path in the areas of quality assurance, material and microstructural properties, intrinsic thermal permeability and dependent stress parameters inhibits enthusiasm for the potential degrees of freedom of the direct metal laser melting process (DMLS). Especially in quality assurance, post-processing destructive measuring methods are still predominantly necessary in order to evaluate the components adequately. The overall objective of these investigations is to gain process knowledge make reliable in situ statements about component quality and material properties based on the process parameters used and emission values measured. The knowledge will then be used to develop non-destructive tools for the quality management of additively manufactured components. To assess the effectiveness of the research design in relation to the objectives for further investigations, this pre-study evaluates the dependencies between the process parameters, process emission during manufacturing and resulting thermal diffusivity and the relative density of samples fabricated by DMLS. Therefore, the approach deals with additively built metal samples made on an EOS M290 apparatus with varying hatch distances while simultaneously detecting the process emission. Afterwards, the relative density of the samples is determined optically, and thermal diffusivity is measured using the laser flash method. As a result of this pre-study, all interactions of the within factors are presented. The process variable hatch distance indicates a strong influence on the resulting material properties, as an increase in the hatch distance from 0.11 mm to 1 mm leads to a drop in relative density of 57.4%. The associated thermal diffusivity also reveals a sharp decrease from 5.3 mm2/s to 1.3 mm2/s with growing hatch distances. The variability of the material properties can also be observed in the measured process emissions. However, as various factors overlap in the thermal radiation signal, no clear assignment is possible within the scope of this work.
First time right is one major goal in powder based 3D metal printing. Reaching this goal is driven by reducing life cycle costs for quality measures, to minimize scrap rate and to increase productivity under optimal resource efficiency. Therefore, monitoring the state of the powder bed for each printed layer is state of the art in selective laser melting. In the most modern approaches the quality monitoring is done by computer vision systems working with an interference on trained neural networks with images taken after exposure and after recoating. There are two drawbacks of this monitoring method: First, the sensor signals - the image of the powder bed - give no direct height information. Second, the application of this method needs to be trained and labeled with reference images for several cases. The novel approach presented in this paper uses a laser line scanner attached to the recoating machine. With this new concept, a direct threshold measure can be applied during the recoating process to detect deviations in height level without prior knowledge. The evaluation can be done online during recoating and feedback to the controller to monitor each individual layer. Hence, in case of deviations the location in the printing plane is an inherent measurement and will be used to decide which severity of error is reported. The signal is used to control the process, either by starting the recoating process again or stopping the printing process. With this approach, the sources of error for each layer can be evaluated with deep information to evaluate the cause of the error. This allows a reduction of failure in the future, which saves material costs, reduces running time of the machine life cycle phase in serial production and results in less rework for manufactured parts. Also a shorter throughput time per print job results, which means that the employee can spent more time to other print jobs and making efficient use of the employee’s work force. In summary, this novel approach will not only reduce material costs but also operating costs and thus optimize the entire life cycle cost structure. The paper presents a first feasibility and application of the described approach for test workpieces in comparison to conventional monitoring systems on an EOS M290 machine.
Production companies are getting more and more aware of the relevancy of energy costs and the environmental impact of their manufactured products. Hence, the knowledge about the energy intensity of new process technologies as metal printing becomes increasingly crucial. Therefore, data about the energy intensity of entire process chains allow a detailed assessment of the life cycle costs and environmental impact of metal printed parts. As metal printing with Laser Powder Bed Fusion (LPBF) is applied from rapid prototyping to serial manufacturing processes more and more, sustainability data are useful to support a valid scale-up scenario and energetic improvements of the 3D-printing machinery as well as peripheral aggregates used in the process chain. The contribution aims to increase the transparency of the LPBF process chain in terms of its energy consumption. Therefore a generalized model to assess sustainability aspects of metal printed parts is derived. For this purpose, the LPBF process chain with the essential pre-, main- and post-processes is evaluated regarding its energy intensity. Here, the sub-processes, for example wet and dry cleaning of the printer, sieving of the metal powder or sand-blasting of the part are analyzed as well as the main printing process. Based on the derived experimental data from an installed, industry-like process chain, a model is created, which tends to generalize the experimental findings to evaluate other metal printed parts and process chain variants in terms of their energy intensity.
Die Feststellung und Entwicklung von Kompetenzen ist ein diskutables und hoch komplexes Forschungsfeld. Wissenschaftlich beschäftigen sich insbesondere die Erziehungswissenschaften, die Pädagogik und die Psychologie sowie die disziplinenübergreifende empirische Bildungsforschung mit der Kompetenzerfassung, sowohl im sekundären als auch im tertiären Bildungssystem. In einem massiven Ausmaß steigt seit der Jahrtausendwende die Fokussierung auf Kompetenzen, insbesondere deren Feststellung und Weiterentwicklung. Die Bedeutung dieser
Themenfelder reicht mittlerweile weit über den Bereich von Schulen und Hochschulen hinaus...
Koppelung von CFD und Prozess-Simulation zur industriellen Auslegung von Spaltöfen für Olefinanlagen
(2003)
Scalar and Joint Scalar-Velocity-Frequency Monte Carlo PDF Simulation of Supersonic Combustion
(2003)
Tertiäre Sicherheit
(2012)
Mit Hilfe kapazitiver Steuerung können Durchführungen hochspannungsführende Leiter durch geerdete Wände in Gebäuden oder Geräten führen. Bei zeitveränderlichen Belastungen (Stoß-, Wechselspannungen) wird die gewünschte Potentialaufteilung durch die Kapazitäten zwischen den leitfähigen Steuerbelägen erzwungen. Bei Gleichspannung ergibt sich eine resistive Steuerung, die bei homogener Leitfähigkeit des Isolierkörpers eine prinzipiell gleichartige Potentialaufteilung ergibt. Durchführungen sind jedoch thermisch hoch belastete Betriebsmittel, in denen starke Temperaturgradienten und in ihrer Folge starke Leitfähigkeitsgradienten entstehen, die zu einer erheblichen Verschiebung der Potentialverteilung führen können [1]. Für Design und Diagnose ist das Verständnis dieser bisher nur theoretisch erfassbaren Vorgänge von großer Bedeutung. Deshalb wurden für experimentelle Untersuchungen zwei identische Durchführungskörper hergestellt, die mit Temperaturfühlern für thermische Messungen bzw. mit Anzapfungen für die Erfassung von elektrischen Potentialen ausgerüstet wurden. Die identische Beheizung beider Leiterrohre erlaubt es, eine Korrelation gemessener thermischer und elektrischer Profile und Transienten herzustellen. Für rückwirkungsfreie Messung der Gleichspannungspotentiale wurde ein Rotationsvoltmeter benutzt. Die Untersuchungen bestätigen das theoretisch erwartete thermisch-elektrische Verhalten und sie zeigen, dass erhebliche transiente und stationäre elektrische Belastungen auftreten können, die im Zusammenhang mit thermischen Transienten und Belastungen gesehen werden müssen. Sie sind beim Design in Rechnung zu stellen und sie zeigen, dass die bei dielektrischen Diagnosemessungen erfassten Materialkenngrößen wichtige Aussagen über den elektrischen Belastungszustand der Durchführung liefern können.
High voltage DC (HVDC) applications become more and more important and the voltage level for energy transportation increases steadily. Hence the design of the DC insulation systems becomes more and more difficult. The difference between HVDC and HVAC insulation systems is that in HVAC the electrical field is distributed according to the permittivities of the materials. Permittivity is only weakly dependent on temperature, so there is no significant difference between the electrical field distribution at room temperature and operating temperature of the insulation system. In HVDC however the electrical field is distributed according to the conductivities of the insulation materials whereas the conductivity is strongly dependent on temperature. This can lead to completely different field distributions at varying temperatures. The investigations presented here show simulation results of HVDC bushing cores in comparison with measurements on those test objects. Simulations and measurements were performed both for temperature distributions and electric potentials of the grading layers in the bushing at DC voltage. For the first time, it was shown by experiment that the FEM simulation can reproduce real DC field distributions very well. It was also shown, that there is a strong influence of temperature gradients or temperature transients on transient and steady-state electrical potential distribution inside the insulation.