Influence Of Structural Parameters On Dynamic Performance Of SR20 Nose Landing Gear Shock Absorber

Up to now,the fleet size of SR20 aircraft of a certain flying unit has reached more than150,undertaking a very large training mission.Because the shock absorber is a life limited part,the flight training facility has to spend a lot of money on replacing the shock absorber every year.Therefore,the flight training facility plans to develop domestic replacement parts of the shock absorber to reduce the annual cost of consumables.In the process of shock absorber design and development,the change of structural parameters has a great influence on its damping performance,so it is extremely critical to choose the appropriate structural parameters in the design process of shock absorber.With the continuous development of computer technology,the development of shock absorber by computer has become the current mainstream trend,which is of great significance to the design and development of home-made shock absorber replacement parts.In order to study the influence of structural parameters on the dynamic characteristic of shock absorber of SR20 nose landing gear,this thesis will analyze its internal structure,working principle and dynamic performance,establishing a three-dimensional internal flow field simulation model of the shock absorber,and analyze the flow field distribution law of the shock absorber under different working conditions by using computational fluid dynamics simulation.The correctness of the simulation model is verified by comparison with the experimental results.Therefore,this thesis uses the simulation model to study the effects of the diameter of the through hole,the size of the oil drain,the diameter of the piston rod and the diameter of the check valve on the dynamic performance of the shock absorber.This provides a theoretical basis for the design and development of domestic shock absorber replacement parts.The main research contents of this thesis are as follows:1.Firstly,the research background and significance of SR20 hydro-pneumatic shock absorber are introduced,and then the computer simulation technology is used to study the dynamic performance of the shock absorber by analyzing and summarizing the research status.2.This article designs the corresponding fixture to disassemble the shock absorber and analyzes its working principle;next,the 3D scanner and Geomagic Design X are use to reverse model the shock absorber.Finally,the 3D solid model of the shock absorber is established using CATIA,and based on the 3D model of shock absorber,the IPC manual is established.According to the shock absorber disassembly process,the disassembly process of SR20 aircraft landing gear shock absorber is used for the preparation of shock absorber manual later.3.The use of bearing press drawing machine,shock absorber pressure tests to obtain the maximum compression stroke of the shock absorber;the vibration absorber bench test is carried out by using the indicator machine.The damping characteristics and velocity characteristics of the shock absorber under different working conditions are obtained by changing the frequency.The influence of different frequencies on the dynamic performance of the shock absorber is analyzed to provide data support for the verification of the simulation model of the shock absorber.4.In order to reduce the workload of calculation,the structure is simplified to a certain extent,and the three-dimensional internal flow field model of the shock absorber is established.The simulation results are compared with the test results.It is proved that the error between the simulation results,which proves the correctness of the simulation model;5.On the basis of verifying the correctness of the simulation model,change the diameter of the through hole,the size of the oil drain,the diameter of the piston rod and the diameter of the check valve to study the influence of different structural parameters on the Dynamic characteristic of the shock absorber.The results show that the diameter of the through hole has less influence on the dynamic characteristic of the shock absorber than the other four parameters.The flow area of the oil drain has a great influence on the dynamic performance of the shock absorber,and the influence of the width of the oil drain is larger than that of the depth of the oil guide groove.With the decrease of the flow area of the oil channel,the recovery damping force and the median compression damping force of the shock absorber increase,and the changes are obvious.The diameter of the piston rod decreases and the damping force of the shock absorber increases.When the diameter of check valve decreases,the recovery damping force of shock absorber remains unchanged,while the median compression damping force increases.By studying the influence of different structural parameters on the dynamic performance of the shock absorber,it can be concluded that the influence of the size of oil drain on the damping force of the shock absorber is greater than that of size of the piston rod and the through hole.The diameter of check valve has a significant effect on the compression damping force of shock absorber,but has no effect on the recovery damping force of shock absorber.Based on the analysis of the above conclusions,it can be concluded that more attention should be paid to the impact of oil drain size and check valve size on the damping force of SR20 shock absorber when designing the replacement parts.