INFLUENCE OF CREEP ON LOW-CYCLE FATIGUE LIFE ASSESSMENT OF ULTRA-SUPERCRITICAL STEAM TURBINE ROTOR

Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.