Influence of elastomeric damper modeling on the dynamic response of helicopter rotors

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Influence of elastomeric damper modeling on the dynamic response of helicopter rotors

Kunz, D.L.

Several modeling approaches that describe the behavior of elastomeric materials used in helicopter rotor lag dampers are examined and evaluated, using laboratory test data. The linear and the nonlinear VKS (Voigt-Kelvin-Solid) model are then used in a simulation of a helicopter rotor startup, and the simulation results are compared to one another and to flight test data. The VKS is described by its mechanical analogy of a dashpot damper, which is parallel-connected to a spring. The spring stiffness and the damping function are either linear or nonlinear. The models created using laboratory test results show that the simple, complex modulus model will yield good predictions of damper energy dissipation, but the simulation results indicate that this model is inadequate for predicting forced response. Although some of the models evaluated performed better than the others, none were free from limitations that would make them unsuitable for some applications. It is recommended that more effort be put into acquiring and analyzing damper test data to facilitate the development of more robust modeling approaches.