Application of a refined time domain elastomeric damper model to helicopter rotor aeroelastic response and stability

A new nonlinear time domain elastomeric damper model is developed for use with helicopter rotor analyses. In hover, the new model exhibits significant low amplitude nonlinearity that is similar to behavior observed in elastomer material coupon bench tests. As the damper amplitude decreases, the lag frequency increases by 60% while the damping decreases by 85%. In forward flight, the model predicts a decrease in damping of approximately 50% due to "dual-frequency" motion. Previous experiments indicate that these predicted trends are accurate and necessary for elastomeric damper modeling. The new damper model also accurately predicts time domain damper loads. As such, it represents an improvement over both traditional complex modulus models and first generation time domain models. Finally, owing to its compact form, accuracy, and straightforward solution procedure, the coupled rotor-damper model is shown to be a useful tool for preliminary rotor-damper design.