AN APPROACH FOR CHARACTERIZING THE AERODYNAMICS/STRUCTURE COUPLING AT THE AIRCRAFT DESIGN STAGE IN THE PRESENCE OF STRUCTURAL NONLINEARITIES

Aeroelasticity is the discipline of the aeronautical engineering that studies the vibration of the aircraft flexible structure as affected by the surrounding air. The aeroelastic behaviour of an aircraft depends basically of four major inputs: structure, inertia, aerodynamics, and flight control systems (aeroservoelasticity). The classical approach considers linear models for the structure, and does not include the effect on structural nonlinearities like freeplay/hysteresis on control surfaces, hardening/softening of the structure with high deformations, and so on. These nonlinearities can modify the classical aeroelastic behaviour of the structure by introducing additional vibration-type instabilities like Limit Cycle Oscillations (LCOs) or Chaotic response. These undamped oscillations, although not catastrophic, have an important influence on the fatigue life of the structure. This report supplies a generic overview of the effect of the concentrated structural nonlinearities on the vibration of the aircraft flexible structure, and describes the current theoretical and experimental methodologies that the aeronautical industry performs to take into account these nonlinearities at the aircraft design stage. Besides this, a novel simulation technology that predicts the response in the presence of structural nonlinearities as a function flight speed, nonlinearity characteristics, and other parameters that could affect the response is presented. The advantages and limitations of this methodology are analysed and a “way forward ” is proposed for future studies