Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Iterative Method to Predict Limit Cycles in Aeroelastic Systems with Freeplay and Coulomb Friction via Describing Functions
Submission Author:
Larissa Drews Wayhs Lopes , SP , Brazil
Co-Authors:
Larissa Drews Wayhs Lopes, Douglas Bueno
Presenter: Larissa Drews Wayhs Lopes
doi://10.26678/ABCM.COBEM2021.COB2021-2326
Abstract
Discontinuous nonlinearities are often present in aeroelastic systems. Particularly, freeplay and friction can change the dynamics of flight, leading the aircraft to limit cycle oscillations (LCO). The prediction of amplitude and frequency of LCO is an important task of engineers, since it can produce failure by fatigue. Typically, LCO are results of marginally stable conditions, characterized by the presence of zero real part of some eigenvalue of the dynamic matrix. Therefore, for linear systems, the search of LCO can be performed by classical linear stability analysis (eigenvalue problem). However, the discontinuity of piecewise nonlinearities produces difficulties to apply such analysis, since the dynamic matrix is no longer unique. A common solution to this problem is to employ the Equivalent Linearization Technique (ELT), where linear equivalent terms are obtained to proper represent the nonlinear system. In this context, this work presents the friction as a linear equivalent viscous damping and, because this equation is dependent on the LCO frequency, typically an output of the ELT, this work also proposes an iterative method to properly apply the ELT to the aeroelastic typical section with simultaneous freeplay and friction in control surface. The results show that the method is suitable for this conditon.
Keywords
describing function, iterative method, equivalent linearization, Freeplay and Friction
