With The Leaves Of The Viscoelastic Damper Rotor Coupled Aeroelastic Dynamics Study

A new nonlinear time domain model for rotorcraft elastomeric dampers is developed in this paper. A damper finite element model is coupled to rotor system equations of motion. The rotor model used in the present study is a rigid-blade flap-lag model. Analytical tools are developed for combined rotor-damper steady state response, stability and transient (time domain) response and damper loads. Steady state response is calculated via direct time integration. Linearized eigenvalue analyses or transient, time domain techniques are used to calculate system stability.Because of strong nonlinearity of the elastomeric damper, analysis of a transient signal is necessary in order to study the stability .it is desirable to have damping identification techniques, which are be fast, can handle a reasonable amount of sensor noise. Three analyses are presented here.The inter-blade damper rotor configuration is also studied in detail. For this configuration, the dampers are connected from blade-to-blade rather than from blade-to-hub. New nonlinear damper kinematic relations are derived. Results from the combined rotor-damper modeling indicate that the new damper model exhibits significant differences from previous modeling approaches. The new model captures important behavior such as reduced damping in forward flight due to dual-frequency motion. It also captures the correct force-displacement (time domain) hysteresis behavior. The new inter-blade damper nonlinear kinematics model confirms experimentally observed results reported in the literature: certain damper attachment offsets can lead to reduced damper 1/rev motion and forces.