Abstract
In this paper, flap-wise, edge-wise and torsional natural frequencies of a variable length blade have been identified. Therefore designers can ensure that natural frequencies will not be close to the frequency of the main excitation forces in order to avoid resonance. The fixed portion and moveable portion of the variable length blade are approximated respectively by a hollow and a solid beam which can be slid in and out. Ten different configurations of the variable length blade, representing ten different positions of the moveable portion are investigated. A MATLAB program was developed to predict natural frequencies. Similarly three-dimensional models of the variable length blade have been developed in the finite element program Unigraphics NX5. Concurrence between MATLAB and Unigraphics NX5 results has been found for the frequency range of interest. This means that an effective method to compute natural frequencies of a variable length blade was developed.
