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70569 Stuttgart
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Room: 2/31
Subject
Bladed disks in turbo aircraft engines are exposed to high vibrational loads. The need to build lighter structures and thus more fuel-efficient engines pushes the current boundaries of the mechanical design and drives the need for novel vibration mitigation approaches.
Vibro-impact absorbers consist of a small mass that is placed inside a cavity of each blade. When the blades are vibrating, the absorbers undergo impacts with the cavity walls. From analyses of isolated blades, it is known that these impacts lead to an irreversible transfer of energy to higher modes, which dissipate the energy on a faster timescale than the critical resonant vibration of a typically lower order mode. This can lead to a reduction of the blade’s resonant amplitude of up to one order of magnitude compared to its resonant response amplitude without absorber.
When considering an entire rotationally periodic assembly blades, i.e., a bladed disk, the vibrational behavior becomes more complicated. The strong nonlinearity due to the vibro-impact absorbers then leads to a plethora of co-existing vibrational responses. Besides responses at which the absorbers are activated in all blades, small perturbances to the symmetric response can lead to the localization of energy in a subset of all blades. These localized responses can potentially lead to a reduced vibration mitigation effect compared to what is known for isolated blades. Nevertheless, the maximum resonant amplitude can always be substantially reduced.
We are always offering bachelor’s and master’s theses on this topic. If you are interested, please send me an e-mail.
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Journal Papers
Weidemann, T.; Bergman, L. A.; Vakakis, A. F.; Krack, M.: Energy transfer and localization in a forced cyclic chain of oscillators with vibro-impact nonlinear energy sinks. Nonlinear Dynamics, 2025. doi: 10.1007/s11071-025-10928-4
Tempelman, J. R.; Weidemann, T.; Flynn, E. B.; Matlack, K. H.; Vakakis, A. F.: Physics-informed machine learning for the inverse design of wave scattering clusters. Wave Motion, 2024. doi: 10.1016/j.wavemoti.2024.103371
Weidemann, T.; Carassale, L.; Denoel, V.; Krack, M.: On the broadband efficacy of impact absorbers. Journal of Sound and Vibration, 2024. doi: 10.1016/j.jsv.2023.118161
Conference Presentations
Gross, J.; Pitzal, M.; Weidemann, T.; Algara, A.; Gulkanov, A.; Salles, L.; Brake, M. R. W.; Schwingshackl, C.; Witteveen, W.; Krack, M.: TRC 2024 - Project 2: Methods for Strongly Discontinuous Contact Events Based on Time Step Integration. International Modal Analysis Conference 2025, Orlando, FL, USA
Weidemann, T.; Bergman, L. A.; Vakakis, A. F.; Krack, M.: Dynamik einer zyklischen Schwingerkette mit Vibro-Impact Absorbern. Deutscher Luft- und Raumfahrtkongress 2024, Hamburg, DE
Vogel, L.; Weidemann, T.; Krack, M.: Experimental quantification of the inter-modal energy scattering in a structure with vibro-impact absorber. European Nonlinear Dynamics Conference 2024, Delft, NL
Weidemann, T.; Vakakis, A. F.; Krack, M.: Dynamics of a cyclic chain of oscillators with vibro-impact absorbers. European Nonlinear Dynamics Conference 2024, Delft, NL
December 2023 – today: PhD student and academic staff at the Institute of Aircraft Propulsion Systems under Prof. Malte Krack
July 2024 – August 2024: Visiting scholar the Imperial College London for the Tribomechadynamics Research Camp (TRC) 2024
May 2023 – October 2023: Visiting scholar at the Grainger College of Engineering of the University of Illinois at Urbana-Champaign (UIUC) with Prof. A. F. Vakakis and Prof. L.A. Bergman
April 2021 – October 2023: Major in Aerospace Engineering, M.Sc. at the University of Stuttgart
October 2017 – April 2021: Major in Aerospace Engineering, B.Sc. at the University of Stuttgart
Experimental quantification of the inter-modal energy scattering in a structure with impact absorber – Bachelor thesis, 2024, University of Stuttgart
To validate or improve the modeling of structures with vibro-impact absorbers, it is crucial to gain experimental insight into their main working mechanism. The latter is based on energy transfer from low to higher modes of the structure that are able to dissipate the mechanical energy on a faster timescale which leads to a reduction of vibration level. In this thesis, the general framework of reconstructing the instantaneous energy distribution between the modes based on measurement data was developed and applied to an existing test rig. The student additionally presented their results at the European Nonlinear Dynamics Conference (ENOC) 2024 in Delft.
Numerical and experimental studies of a non-aligned vibro-impact absorber – Master thesis, 2024, MTU Aero Engines and University of Stuttgart
The blades of turbine rotor stages are exposed to high thermo-mechanical loads. These include vibrational stresses due to external forcing and/or self-excitation. In some cases of particularly high vibration loads, it is necessary to install additional damping systems to reduce the load. In addition to systems that utilize energy dissipation due to friction for damping, damping systems based on the effects of energy transfer caused by impact absorbers have recently been developed. Within this work, the different types of responses of a forced system with disperser are evaluated, at which the cavity is not perfectly aligned with the main direction of oscillation. The dependence on the design of the disperser - regarding the diameter of the sphere and the length of the cavity – is investigated with the aim of determining the most suitable parameter ranges.
Best Presentation Award (2024) First place of the committee ratings as well as the ratings by the other participants for the best presentation at the workshop “Exploiting Nonlinearities in Metamaterials/Metastructures: from Modelling to Applications” organized by the NOLIMAST project.
MT Aerospace Innovation Award (2024) Young Researcher Award of the German Society for Aeronautics and Astronautics (Deutsche Gesellschaft für Luft- und Raumfahrt, DGLR) for the master’s thesis on the “Dynamics of a cyclic chain of oscillaotrs with vibro-impact absorbers”.
Reissner Scholarship (2023) awarded by the Reissner Foundation (Reissner Stiftung) for the time as a visiting scholar at the University of Illinois Urbana-Champaign (UIUC)