Microstructure-Dependent Model for Calculating the Growth Rate of Physically Small and Long Fatigue Cracks

Based on the structural concept of threshold stress intensity factor ranges, the model, describing the growth kinetics of physically small and long cracks, was constructed. The model permits the calculation of lifetime on the growth of physically small and long cracks at regular cyclic uniaxial loads by the data on static mechanical characteristics and a microstructure of the initial material. The model validity was corroborated by fracture toughness results in symmetric cyclic plane bending of VT3-1 titanium alloy specimens in different microstructural states. Calculated kinetic fatigue fracture diagrams are in good agreement with experimental results.