采用疲劳损伤力学的方法分析NiCrMoV钢核电汽轮机低压焊接转子1︰1模拟件接头低周疲劳过程，针对损伤变量表征方法中的弹性模量法和应力幅值法应用的局限性，并考虑循环前期循环软化造成的材料的损伤，提出适用于循环软化材料的低周疲劳全过程损伤变量表征的复合分析法，提高了疲劳过程各阶段材料损伤测量的准确性；提出低周疲劳损伤过程的三阶段损伤模型，将焊接接头的疲劳损伤过程分为应力松弛、微空洞和微裂纹的萌生和扩展以及宏观裂纹的萌生和扩展三个阶段，并用于分析焊接接头的低周疲劳损伤过程。试验结果表明，在NiCrMoV钢汽轮机低压焊接转子接头的低周疲劳损伤过程分析中，采用复合分析法表征损伤变量较弹性模量法和应力幅值法更为合理，且三阶段疲劳损伤模型能很好地反映疲劳损伤过程。

The fatigue damage mechanics is used to analyze the low-cycle fatigue process of 1︰1 simulated sample of NiCrMoV steel nuclear turbine LP welded rotor. A combination analyzing method(CAM) is presented for the limitations of elastic modulus method(EM) and stress amplitude method(SAM) on the definition of fatigue damage variable, which considers material damage during cyclic softening and applies to low-cycle fatigue of cyclic softening materials and improves the accuracy of damage measurement of fatigue process. A new fatigue damage model—three stage model of fatigue damage(TSM-FD) is also proposed to analyze the low-cycle fatigue process of welded joint, which divides fatigue process of welded joint into three stages, as stress relaxation, initiation and propagation of micro hole and crack and initiation and propagation of macro crack. The results show that, in low-cycle fatigue analysis of NiCrMoV steel nuclear turbine LP welded rotor, CAM is more reasonable than EM and SAM to characterize damage variable, and TSM-FD can well describe the evolution of fatigue damage.