Konzeption und Umsetzung eines DSS zur robusten Ressourcenbelegungsplanung im Spezialmaschinenbau

Die operative Produktionsplanung im Spezialmaschinenbau ist durch eine erhöhte Unsicherheit (Informationsdynamik und Stö-rungen) gekennzeichnet, die von APS- und PPS-Systemen bisher zumeist nur unzureichend berücksichtigt wird. Vor diesem Hin-tergrund wird in diesem Beitrag ein Planungsansatz zur Bestim-mung robuster Ressourcenbelegungspläne konzipiert. Die simula-tionsbasierte Dimensionierung von Korrekturfaktoren und die Umsetzung als DSS geben dem Entscheidungsträger die Mög-lichkeit, gemäß seiner Risikopräferenz in die Planung einzugrei-fen. Die bei der Konzeption des Ansatzes fokussierte praktische Anwendbarkeit zeigt sich in den Ergebnissen, die auf den realen Daten eines Unternehmens der Luftfahrtindustrie basieren

Compact structures for single-beam magneto-optical trapping of ytterbium

Today's best optical lattice clocks are based on the spectroscopy of trapped alkaline-earth-like atoms such as ytterbium and strontium atoms. The development towards mobile or even space-borne clocks necessitates concepts for the compact laser-cooling and trapping of these atoms with reduced laser requirements. Here we present two compact and robust achromatic mirror structures for single-beam magneto-optical trapping of alkaline-earth-like atoms using two widely separated optical cooling frequencies. We have compared the trapping and cooling performance of a monolithic aluminium structure that generates a conventional trap geometry to a quasi-planar platform based on a periodic mirror structure for different isotopes of Yb. Compared to prior work with strontium in non-conventional traps, where only bosons were trapped on a narrow line transition, we demonstrate two-stage cooling and trapping of a fermionic alkaline-earth-like isotope in a single-beam quasi-planar structure.Comment: 7 pages, 9 figure

Virtual Element Method for Cross-Wedge Rolling during Tailored Forming Processes

In this work we present an application of the virtual element method (VEM) to a forming process of hybrid metallic structures by cross-wedge rolling. The modeling of that process is embedded in a thermomechanical framework undergoing large deformations, as outlined in [1, 2]. Since forming processes include mostly huge displacements within a plastic regime, the difficulty of an accurate numerical treatment arises. As shown in [3], VEM illustrates a stable, robust and quadratic convergence rate under extreme loading conditions in many fields of numerical mechanics. Numerically, the forming process is achieved by assigning time-dependent boundary conditions instead of modeling the contact mechanics yielding to a simplified formulation. Based on the two metallic combinations of steel and aluminum, different material properties are considered in the simulations. The purpose of this contribution is to illustrate the effectiveness of such a non-contact macroscopic framework by employing suitable boundary conditions within a virtual element scheme. A comparison with the classical finite element method (FEM) is performed to demonstrate the efficiency of the chosen approach. The numerical examples proposed in this work stem out from the DFG Collaborative Research Centre (CRC) 1153 “Process chain for the production of hybrid high-performance components through tailored forming”

Contact Temperature Measurements on Hybrid Aluminum–Steel Workpieces in a Cross-Wedge Rolling Process

The Collaborative Research Center 1153 is investigating a novel process chain for manufacturing high-performance hybrid components. The combination of aluminum and steel can reduce the weight of components and lead to lower fuel consumption. During the welding of aluminum and steel, a brittle intermetallic phase is formed that reduces the service life of the component. After welding, the workpiece is heated inhomogeneously and hot-formed in a cross-wedge rolling process. Since the intermetallic phase grows depending on the temperature during hot forming, temperature control is of great importance. In this paper, the possibility of process-integrated contact temperature measurement with thin-film sensors is investigated. For this purpose, the initial temperature distribution after induction heating of the workpiece is determined. Subsequently, cross-wedge rolling is carried out, and the data of the thin-film sensors are compared to the temperature measurements after heating. It is shown that thin-film sensors inserted into the tool are capable of measuring surface temperatures even at a contact time of 0.041 s. The new process monitoring of the temperature makes it possible to develop a better understanding of the process as well as to further optimize the temperature distribution. In the long term, knowledge of the temperatures in the different materials also makes it possible to derive quality characteristics as well as insights into the causes of possible process errors (e.g., fracture of the joining zone)

Den organiserede idræts betydning for fysisk aktivitet under Corona

Artiklen belyser, hvordan Corona i 2020 påvirkede den voksne befolknings fysiske aktivitetsniveau i fritiden. Analyserne bygger på data fra en spørgeskemaundersøgelse af danskernes bevægelsesvaner under forskningsprojektet Danmark i Bevægelse. Godt 163.000 borgere – 15 år og ældre – besvarede i oktober og november måned 2020 et spørgeskema, som bl.a. omfattede spørgsmål om, i hvilken grad det fysiske aktivitetsniveau var større eller mindre i sammenligning med før Corona. Analyserne viser, at ændringerne i det fysiske aktivitetsniveau i fritiden afhang dels af, hvilke bevægelsestyper den enkelte praktiserer, dels af køn, alder og socioøkonomisk baggrund