Journal cover Journal topic
Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
https://doi.org/10.5194/wes-2017-35
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research articles
21 Aug 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Wind Energy Science (WES).
Benefits of sub-component over full-scale blade testing elaborated on a trailing edge bond line design validation
Malo Rosemeier, Gregor Basters, and Alexandros Antoniou Divison Structural Components, Fraunhofer Institute for Wind Energy and Energy System Technology IWES, Am Seedeich 45, 27572 Bremerhaven, Germany
Abstract. Wind turbine rotor blades are designed and certified according to the current IEC (2012) and DNV GL AS (2015) standards, which include the final full-scale experiment. The experiment is used to validate the assumptions made in the design models. In this work the drawbacks of traditional static and fatigue full-scale testing are elaborated, i. e. the replication of realistic loading and structural response. Sub-component testing is proposed as a potential method to mitigate some of the drawbacks. Compared to the actual loading that a rotor blade is subjected to under field conditions, the full-scale test loading is subjected to the following simplifications and constraints: First, the full-scale fatigue test is conducted as a cyclic test, where the load time series obtained from aero-servo-elastic simulations are simplified to a damage equivalent load range. Second, the load directions are typically applied solely in two directions, often pure lead-lag and flap-wise directions which are not necessarily the most critical load directions for a particular blade segment. Third, parts of the blade are overloaded by up to 20 % to achieve the target load along the whole span. Fourth, parts of the blade are not tested due to load introduction via load frames. Finally, another downside of a state-of-the-art, uni-axial, resonant, full-scale testing method is that dynamic testing at the eigenfrequencies of today's blades in respect of the first flap-wise mode between 0.4 Hz and 1.0 Hz results in long test times. Testing usually takes several months. In contrast, the sub-component fatigue testing time can be substantially faster than the full-scale blade test since (a) the load can be introduced with higher frequencies which are not constrained by the blade's eigenfrequency, and (b) the stress ratio between the minimum and the maximum stress exposure to which the structure is subjected can be increased to higher, more realistic values. Furthermore, sub-component testing could increase the structural reliability by focusing on the critical areas and replicating the design loads more accurately in the most critical directions. In this work, the comparison of the two testing methods is elaborated by way of example on a trailing edge bond line design.

Citation: Rosemeier, M., Basters, G., and Antoniou, A.: Benefits of sub-component over full-scale blade testing elaborated on a trailing edge bond line design validation, Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2017-35, in review, 2017.
Malo Rosemeier et al.
Malo Rosemeier et al.
Malo Rosemeier et al.

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Short summary
This research was conducted with the help of computer models to give argumentations how the reliability of wind turbine rotor blade structures can be increased using sub-component testing (SCT) instead of traditional full-scale blade testing (FST). It was found that the use of SCT can significantly reduce the testing time compared to FST while replicating more realistic loading conditions as they occur in the field.
This research was conducted with the help of computer models to give argumentations how the...
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