Determining Beam Bending Distribution Using Dynamic Information
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AERONAUTICAL AND MARITIME RESEARCH LAB
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As a first approximation, a helicopter rotor blade may be modelled as a cantilever beam. Given the initial deformation of this beam, and using either strain or acceleration at one location along the beam. We can determine the load distribution along the entire beam. We consider load distributions that can vary spatially, but are constant in time except for the initial step input. In the solution we neglect the effects of both aerodynamic and mechanical damping. The separation of variables technique leads to a solution in terms of the beams natural modes. The loading distribution is decomposed in terms of these modes. A finite element simulation of the beams response to a cubic load distribution verifies that this load prediction is possible. We demonstrate that the higher modes of the load prediction are unstable when noise is present in the measurements, but that the lower modes are robust. If the initial beam deformation is unknown, then additional strain or vibration measurement locations may be substituted for the unknown initial deformation.
- Numerical Mathematics