Research On The Manufacture And Usability Of Stainless Small-diameter Split Sleeve

In recent years,the appearance of large aircraft C919 and fifth generation jet fighters 20 indicates the rapid development of China’s aviation industry,and the requirements for anti fatigue manufacturing technology of aircraft is also increasing.Split s leeve cold expansion technology is widely used in the field of aviation,and it can significantly improve the fatigue of fastening holes on the plane.Split sleeve is one of the most important parts of the split sleeve cold expansion,but there is still a gap between our country and abroad for the manufacture technology of split sleeve,especially for the manufacture of small-diameter split sleeve,to a certain extent the development of split sleeve cold expansion technology is limited.Therefore,this paper adopted the method of experiment and simulation,and researched the manufacture and performance of small-diameter split sleeves based on two-axle bending technique.The main work and achievements were as follows:1.Based on the research for the forming condition of 301 stainless steel strip with different thickness,the thick of the strip was optimized out 0.3mm as the research object,which is the most conductive to the manufacture of small-diameter split sleeve.The finite element simulation model of two-axle bending process was established accurately by the strip tension test,and the strip forming radius was obtained by MATLAB image recognition program,the bending process under different rolling process parameters was analyzed by simulation model,with the increase of the hardness of the elastic wheel,the decrease of the diameter of the rigid shaft and the decrease of the strip hardness,the curvature radius of the strip would decrease,and the rigid shaft was the key for the manufacture of 10 mm small diameter split sleeve.2.Based on manufacture requirements for the small-diameter split sleeve,a set of rigid shaft fixture was designed,and its feasibility was verified by strength check and ADAMS dynamics simulation.The main purpose of the design was to achieve stable clamping of rigid shaft with diameter below 8mm,the design used both ends of the fixed support and the new structure of combination bearing,and the anti bending capacity of the shaft was improved by applying axial tension at both ends of the shaft.In the experiment,the fixture c ould successfully clamp rigid shaft whose diameter were both 6mm and 8mm,and straight split sleeves with diameter below 10 mm were successfully manufactured.3.The two-axle bending test was running with the redesigned rigid shaft fixture and hardness of H,3/4H,1/2H of with the same thickness of type 301 stainless steel.Firstly,the interaction between the factors judged by two factorial experiment,and accurate design the orthogonal test with three factors and two levels,the factors were rigid shaft diameter,extrusion and strip hardness,the results of experiment showed that extrusion was the most important factor,then the hardness of strip,and the interaction between diameter of rigid shaft and extrusion,the radius of the rigid shaft was the last one,and the best combination of parameters was chosen for the manufacture of split sleeve with small-diameter.Finally,the single factor experiment was used to research the influence of various factors on radius,with constant extrusion,the increase of the hardness of the elastic wheel,the decrease of the rigidity axis diameter,the decrease of the strip hardness and width w ould reduce radius of the strip,the force of rigid shaft of different hardness strip during bending was measured to make the roll bending forming force quantify.4.The influence of rolling process parameters on strip forming is obtained by simulation and experiment,the split sleeve with diameter of 8mm was successfully manufactured by the rigid shaft with a diameter of 6mm,elastic wheel with hardness as 60 D,301 stainless steel strip with hardness of 1/2H and 3/4H,it’s the present minimum diameter of domestic split sleeve.5.To test the performance of 301 stainless steel split sleeve manufactured in the paper,experimental study of flanging and expansion were carried out.The flanging of straight split sleeves with diameters of both 6mm and 8mm were done,there were no cracks appear.The cold expansion for 2024 Aluminum Alloy samples with the split sleeve with diameters of both 10 mm and 15 mm were carried out to test the hardness change around the hole wall after strengthening,it was found that the hardness increased with the increase of extrusion amount,and the surface quality was good,which verified the reinforcement effect of 301 stainless steel split sleeve cold extrusion.6.To observe the microstructure change of 301 stainless steel strip after roll bending,flanging and cold expansion.The metastable austenite gradually changed into lath martensite,the hardness and strength of the split sleeve increased after cold expansion,the plastic and toughness were decreased,and the severe hardening and deformation occurred,the reflection of the disposable use and the necessity of the slotting,at the same time,the importance of selecting material hardness for split sleeve were also revealed.