Last modified: 2013-04-23
Abstract
This work presents numerical and experimental results of a damage detection technique based on strain energy, with the application on a real size composite helicopter main rotor blade (MRB). The blades from helicopter rotors are a very important structural element - they very long beam-like structures that undergo different load conditions and aerodynamic forces at different parts of it. The damage detection method used in this study is based on the modal strain energy formulation of a beam. Initially, finite element method (FEM) simulations of a composite MRB blade section were carried out to study the technique proposed and afterwards experimental parameters are were extracted via an experimental modal analysis. Vibration modes and natural frequencies were identified by means of a least squares fit (PolyMAX). For this purpose, 55 uniaxial accelerometers were positioned along the blade to measure the most significant vibration modes and an electrodynamic shaker was used to excite the system. Damage was introduced artificially by attaching a small mass to the MRB, changing its global properties this way. Experimental results for the damage detection technique are finally shown, and important remarks concerning sensitivity and robustness of the method are also discussed.
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