Development of Experimental Nonlinear Modal Analysis methods under special consideration of exciter-structure interaction
Final Report Abstract
A measurement method was developed to determine the natural frequency, damping ratio and mode shape as a function of the vibration amplitude. This method, called experimental nonlinear modal analysis, does not require any knowledge of the mathematical form or even the location of the nonlinearities. In contrast to existing measurement methods, the method developed is based on a theoretically sound concept of a nonlinear mode, which also enables the investigation of frictiondamped structures. The method is uses phase-resonant excitation, whereby the control parameters are selected in a theoryriven way. Since the modal parameters change with the amplitude, the vibration mode must be investigated for different amplitudes, which is a decisive contrast to linear modal analysis. Variants for the common forms of shaker-stinger excitation as well as base excitation were implemented and strategies were developed to master unwanted exciter-structure interactions. In order to investigate how robust the developed method is and how accurate the extracted modal parameters are, a series of experimental test rigs was considered. In particular, thin-walled structures and structures with joints were used as test specimens. Among other things, a new test rig was developed for this purpose, which exhibits an unprecedented level of friction-induced damping and a large change in natural frequency with outstanding repeatability. For the first time, a significant change in the vibration mode and the involvement of higher harmonics were also demonstrated. The results confirm that the amplitude-dependent modal characteristics can be precisely determined. In particular, this is also the case with large changes in the natural frequency and with strong, nonlinear damping; in those respects, the developed method goes far beyond the state of the art.
Publications
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A phase resonance approach for modal testing of structures with nonlinear dissipation. Journal of Sound and Vibration, 435, 56-73.
Scheel, Maren; Peter, Simon; Leine, Remco I. & Krack, Malte
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Challenging an experimental nonlinear modal analysis method with a new strongly friction-damped structure. Journal of Sound and Vibration, 485, 115580.
Scheel, Maren; Weigele, Tobias & Krack, Malte
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Experimental assessment of polynomial nonlinear state-space and nonlinear-mode models for near-resonant vibrations. Mechanical Systems and Signal Processing, 143, 106796.
Scheel, Maren; Kleyman, Gleb; Tatar, Ali; Brake, Matthew R.W.; Peter, Simon; Noël, Jean-Philippe; Allen, Matthew S. & Krack, Malte
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Numerical Assessment of Polynomial Nonlinear State-Space and Nonlinear-Mode Models for Near-Resonant Vibrations. Vibration, 3(3), 320-342.
Balaji, Nidish Narayanaa; Lian, Shuqing; Scheel, Maren; Brake, Matthew R. W.; Tiso, Paolo; Noël, Jean-Philippe & Krack, Malte
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Validation of a Turbine Blade Component Test With Frictional Contacts by Phase-Locked-Loop and Force-Controlled Measurements. Journal of Engineering for Gas Turbines and Power, 142(5).
Schwarz, Stefan; Kohlmann, Lukas; Hartung, Andreas; Gross, Johann; Scheel, Maren & Krack, Malte
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Extension of the single-nonlinear-mode theory by linear attachments and application to exciter-structure interaction. Journal of Sound and Vibration, 505, 116120.
Krack, Malte
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A consistency analysis of phase-locked-loop testing and control-based continuation for a geometrically nonlinear frictional system. Mechanical Systems and Signal Processing, 170, 108820.
Abeloos, G.; Müller, F.; Ferhatoglu, E.; Scheel, M.; Collette, C.; Kerschen, G.; Brake, M.R.W.; Tiso, P.; Renson, L. & Krack, M.
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Nonlinear damping quantification from phase-resonant tests under base excitation. Mechanical Systems and Signal Processing, 177, 109170.
Müller, Florian; Woiwode, Lukas; Gross, Johann; Scheel, Maren & Krack, Malte
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Robust and fast backbone tracking via phase-locked loops. Mechanical Systems and Signal Processing, 220, 111670.
Hippold, Patrick; Scheel, Maren; Renson, Ludovic & Krack, Malte
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An iteration-free approach to excitation harmonization. Mechanical Systems and Signal Processing, 233, 112732.
Hippold, Patrick; Kleyman, Gleb; Woiwode, Lukas; Wei, Tong; Müller, Florian; Schwingshackl, Christoph; Scheel, Maren; Tatzko, Sebastian & Krack, Malte
