Modal testing of a simplified wind turbine blade

This paper examines the modal analysis techniques applied in experiments using a uniform and a stepped beam. These simplified shapes are representative of the a wind turbine blade. Natural frequencies have been identified, therefore designers can ensure those natural frequencies will not be close to the frequency of the main excitation forces (1P or NbP with Nb being the number of rotor blades) in order to avoid resonance. The turbine blade is approximated by a cantilever, therefore, it is fully constrained where attached to a turbine shaft/hub. Flap-wise, edge-wise and torsional natural frequencies are calculated. The results found have been compared to numerical results and the exact solution of an Euler-Bernoulli beam. Concurrence is found for the frequency range of interest. Although, some discrepancies exist at higher frequencies (above 500 Hz), finite element analysis proves to be reliable for calculating natural frequencies