Plastic energy dissipation model for lifetime prediction of zirconium and zircaloy-4 fatigued at RT and 400 C

Zirconium and zircaloy-4 are generally used as fuel tubes in pressurized heavy water reactors because of their low neutron absorption cross-section, excellent corrosion resistance, good strength and ductility. Low cycle fatigue properties of zirconium and zircaloy-4 were investigated at RT and 400 C. The microscopic structure was determined using scanning electron microscopy and transmission electron microscopy techniques. On the basis of analyses of fatigue damage mechanism, it is believed that fatigue is an irreversible energy dissipation process. Thus, the plastic dissipation energy per cycle is selected as a fatigue damage variable. The accumulated plastic dissipation energy is calculated at the condition of considering cyclic hardening, saturation and softening characters of zirconium and zircaloy-4 during cycling. The testing results show that they present a power law between the plastic dissipation energy and fatigue lifetime