Time domain Fluidlastic® lag damper modeling

To accurately predict Fluidlastic® lead-lag damper behavior, a nonlinear model is developed. Expanding on previously developed linear models, this model attempts to capture the nonlinear behavior of a Fluidlastic® damper through the addition of nonlinear terms to both the stiffness and damping terms in the model. Comparisons of experimental data to the linear modeling approach demonstrate the linear model's failure to capture high frequency and high displacement behavior. Using a simulated annealing optimization routine and experimental storage and loss moduli, the parameters of the nonlinear model were characterized. The characterized nonlinear model demonstrates the ability to accurately predict trends in both frequency and displacement for both the storage and loss moduli over a frequency range of 0.015 Hz to 15 Hz and a displacement range from 0.005 inches to 0.5 inches. The model is also able to predict the high frequency (1Hz - 15 Hz) nonlinearities with displacement with a maximum percent error of 13% for storage modulus and 36% for loss modulus in the 3.6 - 15 Hz frequency range. Hysteresis loop comparison with experimental data additionally reveals the model's ability to capture the nonlinear behavior of the damper in the time domain.