Effect of Prolonged Thermal Exposure on Low-Cycle Bending Fatigue Resistance of Low-Carbon Steel

Using a dynamic mechanical analyzer, the comparative studies of a low-cycle bending fatigue were carried out for AISI 1022 low-carbon steel after extreme thermal exposure, simulating the severe beyond-design-basis accident at nuclear power plants. In the as-delivered state, the steel has a high resistance to low-cycle fatigue (the fatigue strength at N = 3.5 × 104 cycles (σNf) was 360 MPa). Long-term thermal exposure led to a slight decrease in the resistance to low-cycle fatigue of steel: σNf is decreased by 9%. The influence of AISI 1022 steel structure on the characteristics of fatigue strength and fracture mechanisms is analyzed.