| With the rapid development of Chinese aviation industry,the demand for split sleeve used for cold extrusion strengthening the fastening holes of aircraft fuselage will inevitably increase.At present,the demand for small diameter split sleeves in China is basically imported.In order to narrow the gap of the production technology of split sleeve between China and overseas,this paper base on the two-axle bending technology,researched the forming performance by simulation and experiment using 302 stainless steel as material,explored the theoretical model.The main work and achievements are as follows:1.A new rigid axle fixture was designed to solve the problem of manufacturing straight split sleeve with diameter less than 8 mm.It was carried out by establishing its finite element simulation model,conducting static analysis and rigid axle force analysis,optimizing the size of fixture body,and improving its supporting and fixing methods.And the improved fixture iwas applied in the two-axle bending equipment.The experiment proved that the fixture can realize the stable support of rigid shafts with diameter of 4mm and 5mm.2.The mechanical properties of 302 stainless steel were studied by tensile test.Based on the study of the constitutive model of polyurethane material and the fitting of data under uniaxial tensile test by ABAQUS simulation software,the Mooney-Rivlin constitutive model was established to describe the small deformation of polyurethane material.And the simulation model of two-axle bending was established based on experimental data,and the influence of two-axle flexible bending parameters on the forming diameter of strip were analyzed by simulation.3.Two-axle flexible bending test was carried out with the improved rigid shaft fixture,and the effect of process parameters on the formability of 302 stainless steel strip were studied.The program for identifying the diameter of the forming strip was compiled by MATLAB software,which was used as the basis for the analysis of test results.Through single factor test and orthogonal test,it was found that the degree of influence on the forming diameter of strip from large to small were: the hardness of polyurethane wheel,the extrusion quantity of rigid shaft,strip hardness and the diameter of rigid shaft.The diameter of rigid shaft is the decisive factor that restricts the ultimate forming diameter of strip.Finally,a 5.2 mm straight split sleeve was successfully prepared,which breaks through the minimum diameter of domestic split sleeve.4.Based on the wide plate elastic-plastic bending theory and the contact mechanics model of two-axle bending,through the analysis of the bending process of strip,the calculation method of the forming diameter of strip after roll bending was obtained,and the theoretical calculation formula of the radial force on the rigid shaft was obtained.The theory was verified by the measurement result of the extrusion force of the rigid shaft in two-axle bending. |
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