汽轮机转子疲劳-蠕变损伤的非线性损伤力学分析

转子是汽轮机的核心部件，往往要在高温、复杂应力情况下工作，易产生裂纹萌生。除疲劳作用外，蠕变在转子的寿命损耗中也占有相当的比例。一般低周疲劳约占转子总寿命的80％，而蠕变则占转子总寿命的20％。事实上，对汽轮机转子而言，疲劳和蠕变往往是同时发生并存在着相互的作用。该文采用非线性损伤力学模型估算了国产600MW汽轮机高压转子在实际启停功况下的疲劳-蠕变寿命，考虑了疲劳与蠕变的耦合作用以及多轴应力的影响，并与当前汽轮机疲劳—蠕变寿命估算普遍采用的线性累积损伤理论进行了对比。结果表明：非线性连续损伤力学模型正确地反映了疲劳-蠕变交互作用以及损伤演化的非线性机制，其分析结果比现行理论方法更为准确、可靠。

ON THE FATIGUE-CREEP DAMAGE ANALYSIS OF A STEAM TURBINE ROTOR BY A NONLINEAR CONTIMUUM DAMAGE MECHANICS MODEL

Being an important part of the steam turbine, the rotor is often subject to high temperature and complex stress. Cracks are likely initiate. Apart from fatigue, creep damage also plays an important role in the rotor damage. Generally, low cycle fatigue wears off seventy percent of the life of the rotor and the creep accounts for the remaining thirty percent. However, fatigue and creep always occur with each other. In this study, a nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison results show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory.