Dynamic analysis of a new base excitation testing system for fatiguing wind turbine blades

The importance of testing wind turbine blades to verify the fatigue properties is a critical step in estimating and reducing the operational cost of a wind turbine and maintaining wind as a cost competitive energy source. The research presented in this thesis develops an alternative method of loading blades for fatigue testing known as the Base Excitation Test System (BETS). By adding a flexible spring between root of the blade and the test stand, an input force can be applied at the root of the blade. This reduces the amount of stroke needed in the hydraulic actuators, while achieving the required load distribution required for the fatigue test. The BETS method has potentially more flexibility in saddle mounting configurations, and improved safety and throughput compared to current methods. The BETS method has potential to offer phase locked, dual-axis, resonant testing by modifying the spring stiffness, which results in a more predictable and repeatable loading pattern in both the flap and edge directions. This method has been investigated using a 3D finite element beam model for the blade and testing systems. This work has laid the foundation for developing a prototype design. The new testing method has been developed for a variety of blade lengths, and is scheduled to be prototyped in 2010.