Plasticity-induced fatigue crack closure under plane strain condition with dwelling

Visco-plastic finite element method was used to simulate fatigue crack propagation under constant amplitude cyclic and dwelling tensile loading conditions for a middle-crack specimen made of turbine disc material Udimet720 Li (low inclusion).Node release was used to model the crack propagation at 700°C.The influences of different maximum cycle loads and dwelling time on crack open stress intensity factor were studied under plane strain and constant load stress ratio R=0 condition. The values of normalized crack open stress intensity factor were dispersed under different maximum cycle loads, increased at the beginning of the cycles, and then decreased slightly to a steady value after adequate cycles with the crack growth. The result shows that the increase of dwelling time will increase normalized crack open stress intensity factor. Creep may influence the crack growth rate at elevated temperature and under dwelling condition.