Cyclic plasticity behaviors of steam turbine rotor subjected to cyclic thermal and mechanical loads

In this paper, shakedown and ratchet analyses are performed to investigate the cyclic plasticity behaviors of the steam turbine rotor subjected to cyclic thermal and mechanical loads by employing Linear Matching Method (LMM). Traditionally, the shakedown or ratchet analysis mainly focus on the structure under general cyclic loading condition composed by constant mechanical load and cyclic thermal load, but the investigated steam turbine rotor here is subjected to cyclic mechanical load and cyclic thermal load that vary in phase and out of phase throughout the practical operation load cycle. The failure behaviours of structure under practical operation load cycle is studied and discussed. The novel shakedown and ratchet failure diagrams are plotted by calculating different combinations of cyclic mechanical load and cyclic thermal load. The innovative equation to acquire plastic strain range of the structure under steady state cycle is fitted, which is vital for low cycle fatigue (LCT) assessment. Moreover, detailed step-by-step inelastic analyses are also performed to verify the applicability and effectiveness of the limit boundaries calculated by the LMM. All the investigations demonstrate that the proposed LMM technique is capable of handling practical industrial application with complicated cyclic loads.