Effect Of Spatial Revolute Joint With Clearance On The Shimmy Stability Of Nose Landing Gear In Large Passenger Aircraft

In aircraft taxiing,the ground excitation is transferred to the fuselage through the wheels,and the clearance of each connection position along the way due to design and wear will have an impact on the shimmy stability.It is of great significance to study the effect of nose landing gear clearance on shimmy stability in order to improve nose landing gear design,guide maintenance and enhance aircraft safety.This paper takes a large passenger aircraft’s nose landing gear as the research object,and uses LMS Virtual.Lab software to construct the nose landing gear shimmy multi-rigid body system dynamics model with spatial revolute joint clearance,and conducts simulation research on the shimmy conditions with single clearance and multiple clearances,and tests to verify the correctness of the simulation method,the main research work and results are as follows.1.The dynamics model of the nose landing gear shimmy multi-rigid body system with spatial revolute joint clearance is established.The nose landing gear connection form is analyzed,and the dynamics model of nose shimmy multi-rigid body system with radial clearance and axial clearance is established for three positions: the connection between the turning sleeve and the upper torsion link,the connection between the upper torsion link and lower torsion link,and the connection between the lower torsion link and the piston rod.2.Study on the effect of single spatial revolute joint with clearance effect on the stability of the shimmy.A single-factor approach is used to analyze the effect of single position radial clearance and axial clearance on the critical damping and torsion angle of the nose landing gear shimmy.The results show that the axial clearance at the upper and lower torsion link joints plays a dominant role in the critical damping coefficient of shimmy,and the radial clearance and axial clearance at the turn sleeve and upper torsion link joints and the lower torsion link and piston rod joints have a dominant effect on the torsion angle with smaller values.All three positions will have a small angle of periodic shimmy when the axial clearance increases to a certain value.3.Study of the effect of multiple spatial revolute joint with clearances on the stability of the shimmy.The simulation analyzes the influence law on the stability of shimmy when the spatial revolute joint with clearance exists in three positions at the same time,and the results show that when the shimmy occurs,the maximum periodic torsional angle will be generated when the sliding speed is 30m/s;the maximum radial assembly clearance in three positions are 0.045,0.037 and0.045 mm respectively,and the axial clearance is 0.1mm,when the wear amount is less than 0.01 mm,then the small angle periodic shimmy will not occur.4.Experimental study on the shimmy of nose landing gear with clearance.The single-factor experiment method is used to analyze the effect of the clearance at the upper and lower torque link joints on the shimmy stability,the results show that the radial clearance has no significant effect on the stability of the shimmy,while the axial clearance will reduce the stability of the shimmy when the axial clearance is increased,and 0.127 ° periodic shimmy will occur when the axial clearance is 1mm.