Experimental Study on Residual Stress and Fatigue Life of TB6 Titanium Alloy Connection Hole After Cold Expansion
FENG Pingfa1,2,3, LIU Jiahui1,2, WANG Zibiao4, FENG Feng3, ZHANG Xiangyu1,2, SHEN Yue1,2, ZHANG Jianfu1,2, WANG Jianjian1,2, WU Zhijun1,2, YU Dingwen1,2
1. Beijing Key Laboratory of Precision and Ultra-Precision Manufacturing Equipment and Control, Tsinghua University, Beijing 100084, China;
2. State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, China;
3. Tsinghua Shenzhen International Graduate School, Shenzhen 518055, China;
4. State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
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%.
2023, 
