Study On Sealing And Static Load Characteristics Of Shock Absorber In Nose Landing Gear Of SR20 Aircraft

SR20 aircraft Nose Landing Gear shock absorber as a time-of-life parts,aircraft maintenance manual(AMM)requires every 2000 hours of operation to be renovated,the original manufacturer(OEM)for technical confidentiality reasons,not to any third party to provide renovation technology,so a flight training unit each year to spend a lot of money to replace the shock absorber.In order to reduce the cost of flight training,the flight training unit intends to carry out domestic research on the renovation technology of SR20 aircraft Nose Landing Gear shock absorber,aiming at realizing the autonomous renovation of the component.The sealing characteristics and static load characteristics of the shock absorber reflect the internal quality of the shock absorber.They are extremely important performance indicators in both the design of the shock absorber and the renovation process.In this thesis,the Nose Landing Gear shock absorber of SR20 aircraft is taken as the research object.The sealing characteristics and static load characteristics of the shock absorber are studied by means of simulation and experiment,and the internal quality of the shock absorber of SR20 aircraft Nose Landing Gear is deeply explored.It provides technical and theoretical support for the research and development of domestic shock absorber replacement parts in the future.The specific research contents are as follows :(1)The disassembly of the components of the shock absorber of the SR20 aircraft Nose Landing Gear is realized by designing the corresponding disassembly tool.The reverse modeling is carried out by using the Hex Articulated Arm Scanner 3D scanner and Geomagic Design X software.In Creo5.0 software,the corresponding assembly is carried out through the relative position relationship of each component,and the equal scale three-dimensional model of the shock absorber is completely established.(2)The sealing structure of the shock absorber of the Nose Landing Gear of the SR20 aircraft is mainly based on the Sturt seal.The finite element analysis of the Sturt seal is established based on the ANSYS software platform.The maximum contact pressure distribution cloud diagram and the maximum Von-Mises stress cloud diagram of the O-ring in the Sturt seal structure are obtained by simulation.The influence of the compression ratio of the O-ring on the sealing performance is analyzed.The reciprocating sealing test of the shock absorber with the new sealing ring was carried out to verify the sealing characteristics.(3)Aiming at the SR20 aircraft Nose Landing Gear shock absorber,the experimental modeling research is carried out.The constitutive model and friction model of the shock absorber are established.The improved Lu Gre model function is proposed to describe the complex friction characteristics of the oil-gas shock absorber.The test scheme is designed according to the model.Based on the test data,the static friction force and Coulomb friction force are fitted.Based on the Matlab software platform,the simulink simulation model of friction force and static load characteristics is established,and the simulation values of the comprehensive friction force and static load characteristics of the shock absorber under static load are obtained respectively.(4)Based on the existing research technical data on the static load characteristics of the shock absorber,a reasonable static load characteristic test scheme of the SR20 aircraft Nose Landing Gear shock absorber is designed,and the static load characteristic diagram and the comprehensive friction diagram of the SR20 aircraft nose landing gear shock absorber at the speed of 0.0001m/s are obtained.By comparing with the simulation results and experimental data,it is verified that the established model can accurately characterize the static load characteristics of the shock absorber.Through the research on the sealing and static load characteristics of the shock absorber of the SR20 aircraft Nose Landing Gear,it can be concluded that when the cross-section diameter of the O-ring in the shock absorber is 3.5mm and the compression ratio is 20%,the reliable sealing performance can be obtained,and the friction and wear can be greatly reduced and the service life can be prolonged.The simulation value of the static load comprehensive friction is 128 N,and the error between the test value and the simulation value is less than 5%.The established static load characteristic simulation model has high accuracy,which can provide theoretical support for the establishment of static load characteristic labeling of SR20 aircraft Nose Landing Gear shock absorber after renovation.