Effects of defects on fatigue behavior of TC17 titanium alloy for compressor blades: Crack initiation and modeling of fatigue strength

S-N data of TC17 titanium alloy with surface defects exhibits plateau region (105-109 cycles) feature. The effects of defects are greatly related to the defect size. When the defect size is bigger than the critical one, the crack initiates from the defect, and the fatigue strength σw incorporating the effects of defects could be expressed as σw=Carean, in which area denotes the square root of the projection area of defect perpendicular to the principal stress direction, C and n are parameters. The model is also validated by the experimental results of metallic materials in literature.