Three-Dimensional Fatigue Crack Growth Model of TC4ELI Titanium Alloy at Low Temperature

Fatigue crack propagation behaviors of TC4ELI titanium alloy with different thickness (12.5,9.0,6.0,3.0 mm) at different temperatures(20,-20,-40,-60 ℃)were studied with fatigue testing machine and scanning electron microscope, and the three-dimensional fatigue crack growth model at low temperature of the alloy was established. The results show that due to the closure effect, the fatigue crack propagation rate of the test alloy decreased by decreasing the thickness or temperature, and the material parameters C and n in Paris two-dimensional formula were not constant. Under the framework of three-dimensional fatigue crack growth theory, the material parameters C_eff and n_eff in the revised Paris formula were both constanted, indicating that the established three-dimensional fatigue crack growth model could normalize the fatigue crack growth of the test alloys with different thickness at different temperatures.