Numerical Analysis of Fatigue Effort in Dual Axis Blade Testing
Creators: name: Piwowarczyk, Jakub
name: Czichon, Steffen
name: Rosemeier, Malo
name: Melcher, David
Publisher: name: Zenodo
Year: 2019
Subjects: FEM, Composites

description: As outlined in the IEC 64100-23 [1] standard, type certification of wind turbine blades requires both<br> static and fatigue structural tests. Currently, the fatigue component of blade testing is typically performed<br> uniaxially. The blade is mounted at the root and excited in the flap and lead-lag directions sequentially for a<br> given number of cycles. There is however, a growing interest in dual axis testing, where the blade is excited<br> in the flap and lead-lag directions simultaneously.<br> <br> In this paper, the differences between uniaxial and dual axis testing are investigated through the<br> distribution of fatigue effort of the matrix throughout the blade. For this purpose, a test set up is defined<br> for the DTU 100 Reference blade [2]. Artificial test loads are extrapolated from smaller blades. The dual axis<br> test set up is defined by performing edge and flap excitation simultaneously.<br> <br> Utilizing a shell model of the DTU 100 blade [3], transient analyses in ANSYS APDL are used to find the<br> mean and amplitude strains of each element in the model. These strains were then used to compute the<br> fatigue effort of the matrix of each test with the uniaxial tests being summed according to the Palmgren<br> and Miner damage accumulation method. Comparing the fatigue efforts of the uniaxial and biaxial tests for<br> every element of the shell model, a distribution of the percent differences was obtained. It was found that<br> biaxial tests differed significantly along the blade as compared to uniaxial tests. Further studies will be done<br> to compare fatigue effort in single axis and dual axis testing to fatigue effort due to wind loads as given by<br> load simulations. _______________________________________________________________________________________<br> [1] IEC 61400-23:2014 Full-scale structural testing of rotor blades, International Electrotechnical Commission, 2014.<br> [2] The DTU 10-MW Reference Wind Turbine, Bak et. al. 2013.<br> [3] Rosemeier, Malo. (2018). Dataset of FEPROC Blade Model Verification - 3D Shell and Beam Model [Data set]. Zenodo.<br> http://doi.org/10.5281/zenodo.1494044
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