Analysis And Study Of Factors Influencing The Locking Performance Of Titanium Alloy Self-locking Nut For Aerospace

In 2022,China launched more than 60 space missions,setting a new record.With the launch of the 23 rd satellite,the launch of the C919,the completion of the space station,lunar exploration,fire exploration and sun-to-day activities,China has made remarkable achievements in the field of aviation and aerospace,ushering in a golden era of rapid and all-round development.As an important link of aerospace industry,fasteners are the most widely used and the most widely used products in aerospace aircraft.A medium-sized aircraft can have 2 to 3 million of various fasteners.Self-locking nut,as a common threaded fastener,has the advantages of repeatable disassembly and multiple use,and has reliable anti-seismic and anti-loosening performance.On this basis,the self-locking nut made of titanium alloy also has the characteristics of high hardness,good heat resistance and strong corrosion resistance,making it far ahead in metal materials.Therefore,titanium alloy self-locking nuts are widely used in the field of aerospace.At the same time,the titanium alloy of fasteners can greatly reduce the weight of components,and play a key role in the lightweight of aircraft structure and reducing energy consumption.However,in complex and changeable aerospace application scenarios,the locking performance of titanium alloy self-locking nuts tends to decay due to the coupling effects of vibration,impact,load change and high temperature,and there is a risk of loosening and falling off.If the self-locking nuts are damaged too early after installation,it will lead to irreversible huge consequences.Therefore,based on the factors affecting the locking performance of Ti-6Al-4V self-locking nut of MJ6 specification used by a certain company,this thesis carried out an in-depth study.The main contents are as follows:(1)The working principle and influencing factors of locking performance of titanium alloy self-locking nut are analyzed.Based on the principle of inclined plane,the mechanical model of locking and loosening of titanium alloy self-locking nut was constructed,and the influence formula of locking torque and releasing torque was obtained.The influence of friction force on locking performance was analyzed.Combined with the structural characteristics and material characteristics of titanium alloy self-locking nut,the processing technology and testing method of titanium alloy self-locking nut were experimentally studied.The key factors affecting the locking performance were analyzed and designed,and the problems existed in the machining process of this type of self-locking nut were summarized.(2)Based on ABAQUS software,the closing simulation analysis of titanium alloy hexagon self-locking nuts with different closing outer circle,indentation height and closing amount was carried out to study the changing rule of self-locking nut displacement under different factors.The influence of these three factors on the locking performance of titanium alloy self-locking nut was studied by metallographic test,five-times locking performance test and standard axial load test.The accuracy of simulation results was verified by test data,and the influence trend of single variable factors on the locking performance of self-locking nut was obtained.(3)Based on the experiment,the influence of multi-variable interaction on the locking performance of titanium alloy self-locking nut was studied.Through locking test,permanent deformation test,ultimate axial load test and vibration test,the influence of three variables,including the outer circle of the closing,indentation height and closing quantity,on the locking performance of self-locking nut was tested.Combined with engineering application,The optimal closing combination mode of the self-locking nut of this type titanium alloy was selected(closing outer circle 7.485 mm,closing amount 0.4mm,indentation height 2.0mm).(4)Verify the reliability of optimal closing parameters and self-locking nut processing parameters.Under this parameter,the number of locking test cycles was increased from 5times to 15 times,and batch production verification was carried out.The stability of the process parameters was proved through locking performance test,permanent deformation test and axial load test,and then the process parameters were solidified.