Analysis on stress-strain behavior and life prediction of P92 steel under creep-fatigue interaction conditions

摘要

Considering the flexible operation conditions, the creep-fatigue performance of P92 steel plays a crucial role in manufacturing structural components of ultra-supercritical fossil power plants at 620°C-630°C. The creep-fatigue interaction tests of P92 steel were conducted at 630°C in air with different duration periods, where the duration periods were simultaneously added on the peak tensile strain and valley compressive strain. The addition of hold time resulted in a rapid decrease of fatigue life, where the reduction amplitude increasing with the hold time. There was more than five times reduction as the hold time increased to 300 s. Moreover, the stress relaxation behavior during hold time exhibited a saturation behavior at long dwell time, where the limited relaxed stress gradually approached to the creep threshold stress. Furthermore, a modified strain energy density exhaustion model involving creep threshold stress was proposed and provided more accurate predictions in comparison with the conventional model, reducing the conservatism.