Very high cycle fatigue of TC4 titanium alloy under variable stress ratio: Failure mechanism and life prediction

Axial loading tests with variable stress ratio were performed to investigate the very high cycle fatigue property of TC4 titanium alloy, and a life prediction approach associated with failure mechanism was proposed. The interior failure process is characterized as: (1) occurrence of slip lines or bands on partial α grains, (2) nucleation of micro-cracks within some α grains, (3) coalescence of micro-cracks and formation of granular bright facets, (4) stable macro-crack growth within fisheye (5) unstable crack growth outside fisheye and (6) momentary fracture. The validity of approach is confirmed by the good agreement between predicted and experimental results.