Study On Analyses Of Nose-wheel Shimmy And Tire Dynamics

The aircraft wheel shimmy is a kind of hazardous vibration phenomena that maybe occurs during the operation of aircraft landing-gears, and it is a tremendous threat to the safety of aircraft flight. The happening of nose wheel shimmy is due to the vibrational energy transfer from the high-speed taxiing aircraft to the landing-gears. There is an important theoretical significance and a practical engineering value to ensure the aircraft safety by further studying the problems such as the dynamic properties of aircraft lading-gear and the tire systems, especially the stability analysis of wheel shimmy.A linear and a nonlinear model of aircraft nose-wheel shimmy are proposed in this dissertation to deal with the problems of nose wheel shimmy stability. The analysis method of wheel shimmy stability is presented by solving the differential equations and with the complex eigenvalue method employed mathematically. The parametric tire properties is studied and the influences of the dynamic parameters of aircraft tire to the aircraft nose-wheel shimmy are observed, via the analysis of dynamic characteristics due to the tire viscoelasticity and nonlinearity, base on the Finite Element modeling of tire using ANSYS software.The tire cornering characteristic, which is one of the important factors influencing the wheel shimmy, is studied. The tire rolling characteristic equation and the tire stiffness characteristic equation are re-described in a second-order approximate tire cornering characteristic equation which contains the cornering stiffness, and it can be used to observe the influence of tire cornering characteristic to the wheel shimmy. The nonlinearity due to backlash, Coulomb friction and the quadratic damping are studied. Nonlinear terms are quasi-linearized by the Describing Function Method, the equivalent stiffness and damping coefficients are obtained, and the stability of shimmy systems are analyzed by the complex eigenvalue method.The practical shimmy stability analysis of the aircraft Type-X is conducted, and the conclusions provide a solid foundation to the landing gear shimmy prevention and the improvement of landing gears structural design.