Cumulative fatigue damage in low cycle fatigue and gigacycle fatigue for low carbon–manganese steel

Typical tee and pipe components are subjected to thermal and mechanical loading histories which are variable and divided into two different regimes: low cycle fatigue and high cycle fatigue in steam generator vessel of nuclear power plants. Carbon–manganese steel A42 are often used in such applications. In order to investigate the cumulative damage of low cycle fatigue and gigacycle fatigue, the gigacycle tests have been executed after LCF fatigue cycles damaged. The comparison of VHCF and cumulative fatigue test results shows that LCF load influences the VHCF strength. Continuum Damage Mechanics model is employed to estimate the fatigue damage of LCF and is extended to VHCF regime. The VHCF damage is obtained from varying test resonance frequency of specimen. Moreover, the effect of LCF load on VHCF is studied by an improved cumulative damage model.