Variation of the Modal properties of a Wind Turbine Blade During a Fatigue Testing

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Abstract

Wind turbines are subject to stochastic cyclic loadings which reduce their fatigue life. In this paper, we rely on a Mass Resonance Exciter (MRE) to apply fatigue loadings to a blade. The MRE, high-pressure tubes with hydraulic oil and sensors, substantially alter the distribution of mass, stiffness and structural damping. We will investigate how the test setup has modified the blade, thus verifying the validity of the approach. The blade has been mounted on a block at the Large Scale Facility of DTU Wind Energy Department, and instrumented with accelerometers, to provide the modal properties in the clean configuration. Later, an MRE tuned to excite the first flapwise mode has been added, and the blade has been excited for two million cycles in the flapwise direction. After that, the MRE has been tuned to the first edgewise mode and the blade has been excited again for two million cycles.
At regular intervals, the test has been stopped, to assess the effect of the test setup, as well as the impact of the damage on the modal properties. In each case, the blade modes have been excited using the hammer and pull and release methods. The accelerations along the blade have been processed with system identification algorithms, to provide the modal properties. The test setup has not significantly modified the frequencies of the first flapwise and edgewise modes, while it has altered the frequencies of higher-order modes.
Original languageEnglish
Title of host publicationProceedings of 2020 XI International Conference on Structural Dynamics
EditorsM. Papadrakakis , M. Fragiadakis , C. Papadimitriou
Number of pages4
Publication date2020
Publication statusPublished - 2020
EventXI International Conference on Structural Dynamics - Athens, Greece
Duration: 22 Jun 202024 Jun 2020

Conference

ConferenceXI International Conference on Structural Dynamics
CountryGreece
CityAthens
Period22/06/202024/06/2020

Keywords

  • Wind turbine blade
  • Frequency
  • amping
  • Fatigue

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