Fatigue Crack Propagation Rules of Ti-6Al-4V Titanium Alloy

The fatigue crack propagation rate under constant amplitude loading and the fatigue crack propagation threshold value of Ti-6Al-4V titanium alloy were studied by tests．The results indicate that the fatigue crack propagation threshold values of CT specimens were higher than that of CCT specimens for the same material, and the fatigue crack propagation threshold values of the same kind of specimens decreased linearly with the increase of the test stress ratio. The change rules of fatigue crack propagation rate increased with the increase of average stress and stress level were gained．The material parameters of the Paris and Walker equations were derived from the test data for Ti-6Al-4V titanium alloy. The research results could provide reference for assessment of the material life and damage tolerance design.