Damage detection for helicopter rotor blades in operative conditions

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Damage detection for helicopter rotor blades in operative conditions

Corbelli, A. / Mastroddi, F. / Gennaretti, M.

In the present paper, an FRF-based identification procedure has been applied to evaluate the stiffness variation (i.e., a very simple damage model) of an aeroelastic system, represented by a hovering helicopter rotor blade. Numerical results, obtained in vacuo and in hover condition considering flap and lag DOFs in five blade locations (which corresponds to measure such DOFs), show the capability of the formulation presented to identify the aeroelastic system in terms of spatial matrices: as a proof of the approach, the FRF matrix obtained by identified spatial matrices is in agreement with the original FRF data. It is worth to point out that, for coupled cases (e.g., in vacuo with theta not equal 0 or in hover operative condition) measurement of both flap and lag DOFs is necessary to correctly identify FRFs. Consequently, this is also necessary to evaluate a local damage. Indeed, results on damage detection presented in terms of stiffness variation matrix Delta K show a quite good capability of damage detection, location and quantification. It is also apparent that, for a fixed level of damage, identified damage levels became lower, moving from blade root to blade tip.