@inproceedings{ThumannSchmauserBuchneretal., author = {Thumann, Philipp and Schmauser, Philipp and Buchner, Stefan and Wagner, Marcus}, title = {Festigkeitsbewertung von hochbeanspruchten Kupferkomponenten}, series = {Tagung Auslegung von Bauteilen aus Kupfer und Kupferlegierungen, 14. und 15. Mai 2025, Goslar}, booktitle = {Tagung Auslegung von Bauteilen aus Kupfer und Kupferlegierungen, 14. und 15. Mai 2025, Goslar}, publisher = {Deutscher Verband f{\"u}r Materialforschung und -pr{\"u}fung e.V.}, doi = {10.48447/Cu-2025-569}, abstract = {Es wird gezeigt, wie durch ein ganzheitliches Konzept, beginnend mit der Modellerstellung eines umfangreichen FE-Berechnungsmodells bis hin zur Festigkeitsbewertung unter Verwendung speziell ermittelter Werkstoffkenndaten, die Betriebssicherheit von hochbeanspruchten Kupferkomponenten sichergestellt werden kann. Mit den durchgef{\"u}hrten Werkstoffversuchsreihen an w{\"a}rmebehandelten und weichgegl{\"u}hten Kupferproben aus Cu-ETP R250 wurden neben den Standard-Werkstoffkenndaten wie Streckgrenze Rp, Zugfestigkeit Rm, Bruchdehnung A und Elastizit{\"a}tsmodul E Parameter zur Beschreibung des Werkstoffverhaltens bei zyklischer Belastung bestimmt. Zus{\"a}tzlich wurde wurde in Abh{\"a}ngigkeit der W{\"a}rmebehandlung und der damit verbundenen Ver- oder Entfestigung die Schwingfestigkeit eruiert. Somit ist mit der vorgestellten methodischen Vorgehensweise unter Verwendung tats{\"a}chlicher Werkstoffsteifigkeiten und umfangreicher Schwingfestigkeitsdaten eine Betriebsfestigkeitsbewertung m{\"o}glich.}, language = {de} } @inproceedings{WagnerAlAbadiBuchner, author = {Wagner, Marcus and Al-Abadi, Ali and Buchner, Stefan}, title = {A Numerical-Based Model to Determine the Resonance of the Steel Cores of Transformers}, series = {ARWtr 2022 proceedings : 2022 7th Advanced Research Workshop on Transformers (ARWtr), October (23)24-26, 2022, Baiona, Spain}, booktitle = {ARWtr 2022 proceedings : 2022 7th Advanced Research Workshop on Transformers (ARWtr), October (23)24-26, 2022, Baiona, Spain}, editor = {L{\´o}pez-Fern{\´a}ndez, Xose M.,}, publisher = {IEEE}, isbn = {978-84-09-45157-9}, doi = {https://doi.org/10.23919/ARWtr54586.2022.9959938}, pages = {36 -- 41}, abstract = {The laminated steel core of transformers is one of the main sources of the generated sound, as it is excited by different electromagnetic effects during its normal operation. If the core is excited in its eigenfrequencies, the sound generated by a transformer will increase significantly. Therefore, knowledge of the core's eigenmodes and -frequencies in an early design stage can decrease expenses by avoiding costly modifications that might be required to avoid the sound levels exceeding the specified values after the final factory acceptance test. The current study focuses on developing a core resonance model to determine the eigenmodes and -frequencies of a transformer core. The core's geometry was simplified to a connected-beam structure and a numerical-based approach was applied. The accuracy of the developed model was validated against finite element method (FEM), using ANSYS on a reference core model.}, language = {en} } @inproceedings{BuchnerWagnerHoeller, author = {Buchner, Stefan and Wagner, Marcus and H{\"o}ller, Christoph}, title = {Inverse Acoustic Characterization of Rigid Porous Media using Artificial Neural Networks}, series = {Proceedings of DAS|DAGA 2025, 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, booktitle = {Proceedings of DAS|DAGA 2025, 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, address = {Berlin}, organization = {Deutsche Gesellschaft f{\"u}r Akustik e.V. (DEGA), Berlin}, isbn = {978-3-939296-23-2}, doi = {10.71568/dasdaga2025.142}, pages = {847 -- 850}, abstract = {Porous sound absorbers can be described by the isotropic Biot model, and its fluid phase can be represented by the Champoux-Allard model. To apply these models to a given absorber material, the five acoustical and the four mechanical material parameters must be known. The direct measurement of these parameters is complex and requires cost-intensive measurement equipment. Current inverse methods to obtain these material parameters solve an optimization problem, trying to fit the absorption or impedance curve of the material model to the impedance tube measurement data. Solving this optimization problem, i.e. finding the global minimum, is not guaranteed in an acceptable amount of time, as the optimization problem possesses a multitude of local minima. This work proposes an alternative, data driven approach using artificial neural networks to obtain the material parameters necessary for the characterization of open porous materials. The approach only requires the results of standard impedance tube measurements. The characterization of rigid- and elastic frame materials has been investigated. The datasets were generated using the rigid and elastic frame models for porous absorbers. The approach shows good results for impedance curves generated by the analytical models, the validation with real-world impedance tube measurement data is currently under investigation.}, language = {en} } @article{ThumannBuchnerMarburgetal., author = {Thumann, Philipp and Buchner, Stefan and Marburg, Steffen and Wagner, Marcus}, title = {A comparative study of Glinka and Neuber approaches for fatigue strength assessment on 42CrMoS4-QT specimens}, series = {Strain}, volume = {2023}, journal = {Strain}, number = {e12470}, publisher = {Wiley}, issn = {1475-1305}, doi = {10.1111/str.12470}, pages = {21}, abstract = {In fatigue strength assessment, the methods based on ideal elastic stresses according to Basquin and the less established method based on elastic-plastic stress quantities according to Manson, Coffin and Morrow are applied. The former calculates loads using linear-elastic stresses, the latter requires elasticplastic evaluation parameters, such as stresses and strains. These can be determined by finite element analysis (FEA) with a linear-elastic constitutive law, and subsequent conversion to elastic-plastic loads, using the macro support formula by Neuber. In this contribution, an alternative approach to approximate elastic-plastic parameters proposed by Glinka is compared to the the strain-life method using Neuber's formula, as well as the stress-life method of Basquin. Several component tests on 42CrMoS4-QT specimens are investigated. To determine the input data for the fatigue strength evaluations, the entire test setup is computed by FEA. The nodal displacements from these validated full-model simulations are used as boundary conditions for a submodel simulation of a notch, whose results serve as input for the fatigue strength assessments. It is shown that all approaches provide a reliable assessment of components. Our key result is that the strain-life method using the concept by Glinka for notch stress computation, yields improved results in fatigue strength assessments.}, language = {en} }