1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 unknown
In this project modal analysis has been used to determine the natural frequencies, damping and the mode shapes for wind turbine blades. Different methods to measure the position and adjust the direction of the measuring points are discussed. Differentequipment for mounting the accelerometers are investigated and the most suitable are chosen. Different excitation techniques are tried during experimental campaigns. After a discussion the pendulum hammer were chosen, and a new improved hammer wasmanufactured. Some measurement errors are investigated. The ability to repeat the measured results is investigated by repeated measurement on the same wind turbine blade. Furthermore the flexibility of the test set-up is investigated, by use ofaccelerometers mounted on the flexible adapter plate during the measurement campaign. One experimental campaign investigated the results obtained from a loaded and unloaded wind turbine blade. During this campaign the modal analysis are performed on ablade mounted in a horizontal and a vertical position respectively. Finally the results obtained from modal analysis carried out on a wind turbine blade are compared with results obtained from the Stig Øyes blade_EV1 program.