Aiming at the connection hole of TB6 titanium alloy

the strengthening effect of cold expansion parameters on titanium alloy lug samples was studied. Plastic deformation

residual stress and surface roughness of the hole expanded with different ratios and times were characterized. The tension-tension fatigue life of lug samples before and after cold expansion was tested. Morphology characteristics of fatigue fracture and the reasons for the improvement of fatigue life were analyzed. The results show that cold expansion can hardly improve the surface quality of the hole

but can cause severe plastic deformation of the hole wall and introduce compressive residual stress. With the increase of expansion ratio

the plastic deformation

the peak value and depth of compressive residual stress increase significantly and the attenuation rate decreases

while expansion times has less impact. The fatigue life of lug samples after cold expansion is significantly improved

and the fatigue limit of cold expansion with 3% expansion ratio is increased by at least 38%.