Nonlinear dynamic responses of wing flexible sealing undergoing flapping effect

Abstract

With the increasing demands of higher performance of advanced aircrafts, the flexible sealing have been used to seal the gap between main wing surface and its movable control surface so as to improve stealth performance and control effectiveness. However, during whole flight process undergoing various operation states and severe loadings, the flexible sealing could be separated from control surface and consequently strongly vibrate under the disturbances coming from ambient airflow. In that case, "flapping" motions between flexible sealing and other wing components may cause complicated nonlinear dynamic structural response due to discontinuous boundary conditions along with impact effect. In this study, the static structural responses in multiple states, including original state, installation state and lifting process, are firstly examined based on FEM numerical simulations. The displacements and contact preloads that can influence the dynamic characteristics and responses, changing with flight states and speeds, are given so as to analyze and model the discontinuous boundary conditions. Furthermore, the dynamic responses of the flexible sealing during its flapping motions under these particular discontinuous constraints, considering combination actions of periodic excitation and intermittent impact forces, are comprehensively studied. Our numerical results show that the dynamic displacement amplitude and root moment of flapping motion increase respectively by 86.3 % and 177.9 % than static values. And, a mixing of standing waves and traveling waves of the acceleration and shear stress responses is observed through spatiotemporal evolutions. Generally speaking, the flapping is a dynamic response with broadband spectrum rather than a simple forced vibration, which include superharmonic frequencies of excitation frequency, natural frequency and high frequencies due to impact. More interestingly, significant nonlinear phenomena such as superharmonic resonance and chaos are found due to combination actions of discontinuous constraints and intermittent impacts. To deeply explore the nonlinear behaviors of this flapping motion, an analytical model including stiffness jump and impact force is developed, and the Runge-Kutta algorithm is used to obtain the solutions of the nonlinear system. The phase diagram and Poincare section of the analytical solutions give similar qualitative results with our numerical simulations