Dynamic Modeling And Analysis Of Helicopter Rotor Elastomeric Lag Damper

Elastomeric lag damper is the important component part of helicopter rotor hub and can providesufficient stiffness and damping for lag motion of the helicopter blades to suppress the helicopter"ground resonance" and "air resonance" and to improve the dynamic stability of the helicopter. Thecomplex modulus and dynamic amplitude of helicopter elastomeric lag damper have the significantnonlinear characteristics. When the lag damper is in dual-frequency excitation, the complex modulusfall sharply and it brings great influence on the dynamic stability of the helicopter. It’s hard todescribe the relationship between stress and strain through the linearization of the complex modulus.In this thesis the complex modulus of elastomeric lag damper and stress-strain relationship have beenmodeled through the changes in dynamic amplitudes.In this thesis the models of elastomeric lag damper in frequency-domain and time-domain havebeen established. By using the model in frequency-domain, the variation relationship of complexmodulus with dynamic amplitude of the elastomeric lag damper in single frequency anddual-frequency excitation was analyzed. The established model in single frequency excitation canwell reflect the variation of experimental complex modulus with dynamic amplitude. But indual-frequency excitation the changes in complex modulus have a certain error comparing with theexperimental values. Using an improved model, the changes in complex mode in dual-frequencyexcitation can be predicted very well. By using the model in time-domain, the stress-strainrelationship of the elastomeric lag damper under shear force was analyzed. The improved model canwell reflect the nonlinear characteristics of elastomeric lag damper. In this thesis the model calculationparameters in time-domain were optimized by using particle swarm optimization. The optimizedstress-strain relationship can be better consistent with the experimental curves. The relationshipbetween complex modulus and strain amplitude and the stress-strain curve relationship under theaction of static displacement were calculated according to the optimized model parameters. Theresults show that the curve relationship plotted according to the optimized model parameters can wellreflect the experimental curve relationship.