Influence of Surface Defect on the High Cycle Fatigue behavior of TB6 Titanium Alloy

High cycle fatigue tests of TB6 titanium alloy with surface defects of impact pit and scratch were carried out with different cyclic stress amplitude and different defect size. Thereafter SEM was employed to analyze the fatigue fracture morphology. Experimental results indicate that a surface defect like impact pit and scratch will decrease the fatigue life of TB6 alloy and the degradation of material’s fatigue resistance will be intensified with the increase of the defect depth. Fatigue crack initiation sites were figured out through SEM analysis, which was at the edge of impact pit and at the bottom for the scratch defect. Furthermore, the fatigue strength prediction models for the impact pit and scratch cases respectively were proposed based on Murakami’s empirical formula, and the predicted values of new models were in good agreement with fatigue test results.