Study On Interference Bolt Connection Based On Shape Recovery Of Fe-Mn-Si Memory Alloy

Fatigue damage is the main destructional form of aircraft structure.So it is importance to improve the fatigue resistance of aircraft structure and achieve long life and high reliability in the aspect of advanced aircraft manufacturing technology.As a hole-axle connection assembly method with large interference,the interference fit bolt connection is an important technology to improve the fatigue life of aircraft structure.In order to solve the problem that traditional fasteners can't realize large interference uniform connection.,the design idea of interference bolt connecting by the shape memory recovery characteristics of Fe-Mn-Si memory alloy is proposed.Meanwhile,the radial recovery characteristics of Fe-Mn-Si memory alloy and the interference connection characteristics of Fe-Mn-Si memory alloy and 6061-T651 aluminum alloy are researched.Based on the law of volume constancy inside plastic deformation,the relationship between radial pre-strain and axial pre-strain,radial recovery strain and axial recovery strain of Fe-Mn-Si memory alloy was deduced.With the radial recovery characteristic test,it can be shown that the calculation error of radial pre-strain and radial recovery strain of Fe-Mn-Si memory alloy increases with the increasement of pre-strain.The calculation of the radial pre-strain is greater than the measured radial pre-strain,and the calculated value of radial recovery strain is less than the measured radial recovery strain.The maximum axial recoverable strain and radial recoverable strain of Fe-Mn-Si memory alloy are 2.31%and 1.41%,respectively.Meanwhile,the radial and axial shape recovery ratio decrease with the increase of pre-strain.It can be seen in the influence of main factors on radial recovery characteristics that the radial and axial shape recovery ratio of Fe-Mn-Si shape memory alloy increase with the increasement of heating recovery temperature and remain stable at 300 degrees Celsius.With the analysis of Shockley incomplete dislocation resistance formula,it can be seen that thetotal dislocation density and the resistance of phase transformation Shockley incomplete dislocation movemen is proportional to the pre-strain,whitch results in the reduction of the radial and axial shape recovery ratio of Fe-Mn-Si memory alloy.And the solid solution temperature will affect the shape memory effect by the total dislocation density and parent phase strength in the structure of Fe-Mn-Si memory alloy.When the annealing temperature is between 900?and 1000?,the radial and axial shape recovery ratio of Fe-Mn-Si shape memory alloy are maximalBased on the theory of thick-walled cylinder,the formula between interference and aperture,radius of plastic zone under elastic-plastic deformation is deduced,and then the relationship between interference stress and radius of plastic zone is also obtained.After interference bonding,the relation curve between interference and interference force of Fe-Mn-Si memory alloy/6061-T651 aluminum alloy is measured by experiments.Although the error between the interference force test value and the theoretical calculation value exisits(7%-17%),but the variation trend was consistent.From the fatigue test of Fe-Mn-Si interference bolt/6061-T651 aluminium alloy interference bolt connection,it can be seen the fatigue life of aluminium alloy joint increases with the increasement of interference.Based on the Workbench software,the weak position of fatigue life obtained by the simulation is consistent with that by the actual test.The stress concentration in X direction is gradually away from the hole edge When the interference increases,which indicates that the better the effect of stress support at the hole edge and the smaller the stress concentration will induce by the greater interference;while the stress concentration in Y direction increases with the increase of interference,So excessive interference may reduce the fatigue life of the connecting plate.