Nonlinear, temperature-dependent, fluidlastic lead-lag damper modeling

To accurately predict Fluidlastic® lead-lag damper behavior throughout its operational envelope, a nonlinear, temperature-dependent model is developed. Expanding on previously developed linear and nonlinear models, this model attempts to capture the nonlinear temperature-dependent behavior of a Fluidlastic damper through the addition of nonlinear ADF and slider elements in parallel with the stiffness and damping nonlinear terms of the model. Comparison studies have determined the importance and the effect of the nonlinear parameters to the model. A simulated annealing optimization routine and experimental storage and loss moduli are used to characterize the parameters of the nonlinear model over a range of regular operating temperatures, from a low temperature of -40° F up to a high temperature of 140° F. The characterized nonlinear model demonstrates the ability to capture trends in both frequency and dynamic displacement for both the storage and loss moduli over a range of frequencies (0.35 Hz - 15 Hz), a range of displacements (0.005 in - 0.3 in), and a range of temperatures (-40°F - 140°F). The model is able to predict the more pronounced nonlinearities at the higher frequencies, higher displacements, and large temperature changes. For temperatures down to -4°F, errors for both the storage and loss moduli are around 10%, with maximum errors in the extreme regions of approximately 30% or less. The coldest temperature, where the largest nonlinear behavior is exhibited, has larger errors, with the average error under 30% and maximum errors around 160%. Comparison of the experimental and predicted hysteresis loops further demonstrate the ability of the model to capture the Fluidlastic lead-lag damper behavior throughout its operating zone.