Subsurface crack nucleation and growth behavior and energy-based life prediction of a titanium alloy in high-cycle and very-high-cycle regimes.

• Duplex S-N curve associated with surface and subsurface failures under R = 0 is more obvious. • Deflection of crack surfaces contributes to the slow crack growth especially in the FCA. • Subsurface failure mechanism with the determination of stress intensity factors is elucidated. • An energy-based life prediction approach with crack nucleation and growth is proposed. Fully reversed and pulsating tension fatigue tests were performed to clarify the subsurface failure behavior of TC11 titanium alloy in high-cycle and very-high-cycle regimes. The deflection of crack surfaces induces the premature contact of crack surfaces and slow crack growth. The whole failure processes mainly include: (i) nucleation of microcracks, (ii) coalescence and growth of microcracks, (iii) formation of facet cluster area, (iv) early macrocrack growth, (v) formation of fisheye, (vi) unstable macrocrack growth and (vii) momentary fracture. Based on the modeling of crack nucleation and growth, an energy-based approach is well proposed to predict the total fatigue life. [ABSTRACT FROM AUTHOR]