Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model

Christian R. Brackbill, Edward Smith, George A. Lesieutre

Research output: Contribution to conferencePaper

1 Citation (Scopus)

Abstract

A new nonlinear time domain elastomeric damper model is developed for use with helicopter rotor analyses. A methodology is developed for integrating the new time domain damper model with a helicopter rotor aeroelastic response and stability analysis. Damper finite element equations are coupled with rotor blade equations of motion and analyzed simultaneously. Analytical tools are developed for determining steady state response, stability, and transient response of the combined system. The new damper model is shown to be an improvement over traditional complex modulus models and first generation time domain models. In hover, the new model exhibits significant low amplitude nonlinearity: as the amplitude decreases, the lag frequency increases by 60% and the damping decreases by 85%. In forward flight, the model shows a decrease in damping of approximately 50% due to "dual-frequency" motion. Damper response and loads are also examined. For certain flight conditions, the damper loads predictions of various models differ significantly. A complex modulus model predicts a 90% higher peak dynamic damper load than the current model. A baseline ("first generation") time domain predicts 40% lower peak damper load. Basic damper sizing (design) issues are also examined. For an increase in damper area while maintaining the design dynamic lag stiffness, the current damper model predicts an increase in static lag angle. A complex modulus model does not capture this effect. A reduced damper operating strain range increases damping in forward flight, but reduces low-amplitude damping in hover, and can only be achieved by significantly increasing the damper size.

Original languageEnglish (US)
StatePublished - Dec 1 2000
Event41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000 - Atlanta, GA, United States
Duration: Apr 3 2000Apr 6 2000

Other

Other41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000
CountryUnited States
CityAtlanta, GA
Period4/3/004/6/00

Fingerprint

Helicopters
Damping
Helicopter rotors
Dynamic loads
Transient analysis
Turbomachine blades
Equations of motion
Rotors
Stiffness

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Mechanics of Materials
  • Building and Construction
  • Architecture

Cite this

Brackbill, C. R., Smith, E., & Lesieutre, G. A. (2000). Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model. Paper presented at 41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000, Atlanta, GA, United States.
Brackbill, Christian R. ; Smith, Edward ; Lesieutre, George A. / Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model. Paper presented at 41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000, Atlanta, GA, United States.
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abstract = "A new nonlinear time domain elastomeric damper model is developed for use with helicopter rotor analyses. A methodology is developed for integrating the new time domain damper model with a helicopter rotor aeroelastic response and stability analysis. Damper finite element equations are coupled with rotor blade equations of motion and analyzed simultaneously. Analytical tools are developed for determining steady state response, stability, and transient response of the combined system. The new damper model is shown to be an improvement over traditional complex modulus models and first generation time domain models. In hover, the new model exhibits significant low amplitude nonlinearity: as the amplitude decreases, the lag frequency increases by 60{\%} and the damping decreases by 85{\%}. In forward flight, the model shows a decrease in damping of approximately 50{\%} due to {"}dual-frequency{"} motion. Damper response and loads are also examined. For certain flight conditions, the damper loads predictions of various models differ significantly. A complex modulus model predicts a 90{\%} higher peak dynamic damper load than the current model. A baseline ({"}first generation{"}) time domain predicts 40{\%} lower peak damper load. Basic damper sizing (design) issues are also examined. For an increase in damper area while maintaining the design dynamic lag stiffness, the current damper model predicts an increase in static lag angle. A complex modulus model does not capture this effect. A reduced damper operating strain range increases damping in forward flight, but reduces low-amplitude damping in hover, and can only be achieved by significantly increasing the damper size.",
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Brackbill, CR, Smith, E & Lesieutre, GA 2000, 'Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model' Paper presented at 41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000, Atlanta, GA, United States, 4/3/00 - 4/6/00, .

Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model. / Brackbill, Christian R.; Smith, Edward; Lesieutre, George A.

2000. Paper presented at 41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000, Atlanta, GA, United States.

Research output: Contribution to conferencePaper

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N2 - A new nonlinear time domain elastomeric damper model is developed for use with helicopter rotor analyses. A methodology is developed for integrating the new time domain damper model with a helicopter rotor aeroelastic response and stability analysis. Damper finite element equations are coupled with rotor blade equations of motion and analyzed simultaneously. Analytical tools are developed for determining steady state response, stability, and transient response of the combined system. The new damper model is shown to be an improvement over traditional complex modulus models and first generation time domain models. In hover, the new model exhibits significant low amplitude nonlinearity: as the amplitude decreases, the lag frequency increases by 60% and the damping decreases by 85%. In forward flight, the model shows a decrease in damping of approximately 50% due to "dual-frequency" motion. Damper response and loads are also examined. For certain flight conditions, the damper loads predictions of various models differ significantly. A complex modulus model predicts a 90% higher peak dynamic damper load than the current model. A baseline ("first generation") time domain predicts 40% lower peak damper load. Basic damper sizing (design) issues are also examined. For an increase in damper area while maintaining the design dynamic lag stiffness, the current damper model predicts an increase in static lag angle. A complex modulus model does not capture this effect. A reduced damper operating strain range increases damping in forward flight, but reduces low-amplitude damping in hover, and can only be achieved by significantly increasing the damper size.

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Brackbill CR, Smith E, Lesieutre GA. Helicopter aeroelastic response and stability using a refined time domain elastomeric damper model. 2000. Paper presented at 41st Structures, Structural Dynamics, and Materials Conference and Exhibit 2000, Atlanta, GA, United States.