Studying the Effect of Freeplay on Nose Landing Gear Shimmy Using a Fully Nonlinear Model

2018 ◽  
Author(s):  
Mohsen Rahmani ◽  
Kamran Behdinan
Keyword(s):  
Nonlinear Model ◽  
Nonlinear Stability ◽  
Dynamic Models ◽  
Landing Gear ◽  
Stability Boundaries ◽  
Fully Nonlinear ◽  
Freeplay Nonlinearity ◽  
Stability Maps ◽  
Long Time ◽  
Time Histories

Shimmy is a common instability of landing gear systems which has been known for a long time. Yet, it is often studied using simplified dynamic models in which the chief system nonlinearities are neglected. Particularly, the influence of worn components and loose joints manifesting itself as a freeplay nonlinearity has been only touched upon in few works. The present paper utilizes a fully nonlinear landing gear dynamic model to obtain nonlinear stability boundaries and to study the onset, severity, frequency jumps, and mode shifts of the system as a result of the torque link freeplay. Using stability maps in the parameter space and time histories of the oscillations the degrading effect of excessive clearance and wear in the torque links is demonstrated, which in turn offers insights for designing shimmy-free landing gears.

Some Nonlinear Behaviour of Freak Waves and Envelope Solitons

2002 ◽  
Author(s):  
Didier Clamond ◽  
John Grue
Keyword(s):  
Time Evolution ◽  
Nonlinear Model ◽  
Nonlinear Behaviour ◽  
Freak Waves ◽  
Fully Nonlinear ◽  
Weakly Nonlinear ◽  
Envelope Solitons ◽  
Long Time ◽  
Long Time Evolution ◽  
The Right

The nonlinear Schro¨dinger-like equations are widly used models for investigating the evolution of surface gravity waves with narrow-banded spectra. We numerically compare one of these simplified models with a fully nonlinear one. In particular, we study the long time evolution of wave groups. Although the simplified model predicts the right number of soliton formed, their behaviour and long time evolution is not well described. Solitons interact differently with the two models. During the interaction, freak waves are formed. Their occurence is more frequent with the fully nonlinear model. A more interesting phenomemon is, during the formation of freak waves, the wave envelope oscillates rapidly. This “intermittence” is not at all predicted by any weakly nonlinear model.

The Nonlinear Behavior of Heavy-Duty Truck Combinations With Respect to Straightline Stability

1989 ◽  
Vol 111 (4) ◽  
pp. 577-582 ◽  
Author(s):  
A. Stribersky ◽  
P. S. Fancher
Keyword(s):  
Nonlinear Stability ◽  
Bifurcation Theory ◽  
Nonlinear Behavior ◽  
Stable Limit ◽  
Heavy Duty ◽  
Stability Boundaries ◽  
Stability Behavior ◽  
Heavy Duty Truck ◽  
Straight Line ◽  
Stable Limit Cycles

A comparison of the nonlinear stability behavior of the steady state straight line motion of truck combinations with and without a second trailer is shown. These investigations have been done by applying bifurcation theory. Stability boundaries in the parameter space and the corresponding bifurcation solutions are given. Depending on the loading conditions, unstable and also stable limit cycles have been found. Particular emphasis is given to the influence of the frictional coupling between tire and road on the nonlinear stability behavior of these vehicles.

Fully Nonlinear Model of Cables

AIAA Journal ◽  
1992 ◽  
Vol 30 (12) ◽  
pp. 2993-2996 ◽  
Author(s):  
Perngjin F. Pai ◽  
Ali H. Nayfeh
Keyword(s):  
Nonlinear Model ◽  
Fully Nonlinear

Comparisons of Two Different Mixed Eulerian-Lagrangian Schemes Based on a Study of Flare-Slamming Hydrodynamics

1996 ◽  
Vol 118 (3) ◽  
pp. 174-183
Author(s):  
M. L. Wang ◽  
A. W. Troesch ◽  
B. Maskew
Keyword(s):  
Free Surface ◽  
Comparative Study ◽  
Numerical Simulations ◽  
Fourier Coefficients ◽  
Fully Nonlinear ◽  
Time Stepping ◽  
Time Histories ◽  
Nonlinear Free Surface ◽  
Simulated Time ◽  
Flare Slamming

A comparative study of two different mixed Eulerian-Lagrangian methods is presented. Representative numerical simulations of oscillatory flare-slamming flows are given. Computations based on these two different numerical schemes, i.e., a desingularized method using Rankine ring sources and a source-doublet panel method (e.g., USAERO/FSP©), are compared with experiments. Fourier coefficients of the simulated time histories and experimentally measured forces are given for detailed error comparisons. The numerical simulations demonstrate the ranges of applicability of these two methods. Both are shown to be efficient and robust time-stepping schemes for the fully nonlinear free-surface problem studied here.

Dynamic models for the contact analysis of a tensioned beam with a moving oscillator

2013 ◽  
Vol 228 (4) ◽  
pp. 676-689
Author(s):  
Kyuho Lee ◽  
Jintai Chung
Keyword(s):  
Natural Frequency ◽  
Nonlinear Model ◽  
Frequency Ratio ◽  
Dynamic Models ◽  
Equations Of Motion ◽  
Contact Analysis ◽  
Contact Forces ◽  
Accurate Analysis ◽  
Moving Oscillator ◽  
Velocity Decrease

Several dynamic models are proposed for the contact analysis of a tensioned beam with a moving oscillator. Depending on whether the strain and stress used to derive the equations of motion are nonlinear, four models are established to analyze the beam deflections and the contact force between the beam and moving oscillator. We find that the differences in the contact forces and deflections computed with the models become large as the beam tension and moving velocity decrease and the natural frequency ratio of the oscillator to the beam increases. The nonlinear model derived with nonlinear strain and stress is desirable for an accurate analysis.

Nonlinear Dynamics of a Pendulum Excited by a Crank-Shaft-Slider Mechanism

2014 ◽  
Author(s):  
Rafael H. Avanço ◽  
Hélio A. Navarro ◽  
Reyolando M. L. R. F. Brasil ◽  
José M. Balthazar
Keyword(s):  
Nonlinear Dynamics ◽  
Lyapunov Exponents ◽  
Nonlinear Model ◽  
Special Interest ◽  
Initial Conditions ◽  
Phase Portraits ◽  
Bifurcation Diagrams ◽  
Numerical Techniques ◽  
Vertical Excitation ◽  
Time Histories

In this analysis, we consider the dynamics of a pendulum under vertical excitation of a crank-shaft-slider mechanism. The nonlinear model approaches that of a classical parametrically excited pendulum when the ratio of the length of the shaft to the radius of the crank is very large. Numerical techniques are employed to investigate the results for different parameters and initial conditions. Lyapunov exponents, bifurcation diagrams, time histories and phase portraits are presented to explore conditions when the pendulum performs or not full rotations. Of special interest are the resonance regions. Rotations together with oscillations and chaos were observed in some resonance zones.

Sign in / Sign up

Export Citation Format

Share Document