1 AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China 2 Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation, Beijing 100095, China 3 Key Laboratory of Science and Technology on Aeronautical Materials Testing and Evaluation of Aero Engine Corporation of China, Beijing 100095, China 4 Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation, Beijing 100095, China 5 AVIC Changhe Aircraft Industry (Group) Corporation Ltd., Jingdezhen 333000, China
Abstract: The fretting fatigue fracture mechanism of TB6 high strength titanium alloy under tension-torsion multiaxial stress was studied. Based on macro and micro observation, residual stress testing and computer simulation, the difference of the fretting fatigue life of the lugs with different treated conditions under tension-torsion fatigue test stress was analyzed. The characteristics of fretting fatigue crack initiation and propagation under tension-torsion fatigue test were studied, and the mechanism of fretting crack initiation was revealed. The results show that fractures propagation area of twice extrusion lugs is larger. After twice extrusion, the total life of fretting fatigue of lugs is greatly extended, and the crack initiation life accounts for more than 95% of the total life. The driving force of the crack initiation is lower and the resistance against crack initiation is better. Each fracture originates from the marks on the inner hole of lugs have heavier fretting wear. After extrusion strengthening, a higher residual compressive stress layer and a tissue strengthening layer are formed on the hole wall, which can effectively inhibit the initiation and propagation of the cracks. The formation of fretting wear layer in the inner hole of lugs is the result of the combined action of mechanical mechanism and thermal induction mechanism, and the final wear form of lugs is fatigue wear.
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