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Numerical and experimental analysis of a segmented wind turbine blade under assembling load effects

In this paper, numerical and experimental modal analysis of a segmented wind turbine blade 
assembled with a steel threaded shaft and a nut are presented. The blade segments are built 
by a 3D printer using ABS material. The experimental modal parameters identification has 
been achieved using the Eigen system Realization Algorithm (ERA) method for different values 
of the blade segments assembly force caused by the nut tightening torque. Furthermore, 
a three dimensional finite element model has been built using DTK18 three node triangular 
shell elements in order to model the blade and the threaded shaft structure, taking into 
account the additional stiffness caused by the nut tightening torque. This study covers the 
blade segments assembly force effects on the rotating blade vibration characteristics. The 
numerical model is adjusted and validated by the identified experimental results. This work 
highlights the significant variation of the natural frequencies of the segmented wind turbine 
blade by the assembling load of the segments versus blade rotating speed.