Fatigue strength prediction of TC4 titanium alloy following foreign object damage based on contour feature

Foreign object damage (FOD) is a common accident that happens in aeroengines, especially in fan and compressor blades. Accurate prediction of the fatigue strength of the fan/compressor blade materials following FOD is important for the repair and maintenance of aeroengines. This paper was based on the experiment part of Ref. [13], and fatigue strength prediction of TC4 alloy following simulated FOD was carried out by the theory of critical distances (TCD). The FOD notch bottom morphology was characterized by structured light scanning, and a superimposed notch model containing the characteristic of FOD contour was proposed for fatigue prediction. The results show that the prediction based on the FOD macro size overrates the fatigue strength. This overrated prediction is mainly caused by ignorance of the irregular local defects at the FOD notch bottom. By taking the local defects into consideration, the superimposed notch model can effectively improve the prediction accuracy of fatigue strength, and the relative error is within ±30 %.