核电用690镍基合金的应变疲劳行为及寿命预测

Strain fatigue behavior and life prediction of nickel based alloy 690 for nuclear power plants

研究了某核电用690镍基合金在4种应变幅控制下的低循环应变疲劳,分析了疲劳断裂行为、应变疲劳寿命数据和循环应力-应变数据,给出了该690镍基合金的应变疲劳参数。结果表明,690镍基合金的低循环应变疲劳裂纹主要以穿晶断裂方式萌生于试样的自由表面并向内部扩展。4种应变幅控制下的应变疲劳寿命均高于美国阿贡国家试验室(ANL)给出的设计寿命。分别用Manson-Coffin方程和Langer方程对应变幅-疲劳寿命数据进行拟合,给出了预测方程;弹性应变幅、塑性应变幅与载荷反向周次的关系和塑性应变幅与循环应力幅的关系在对数坐标系下均呈线性关系。

The strain fatigue tests under different strain amplitudes of nickel based alloy 690 used for nuclear power plants were performed.The fatigue behavior,fracture surfaces,strain-fatigue life data and cyclic stress-strain data were analyzed,the strain fatigue parameters of the alloy were obtained. The results show that the fatigue cracks of the alloy initiated at the specimen surface mainly in transgranular mode and propagated internally until final fracture by ductile dimple rupture. The fatigue lives under different strain amplitudes were higher than the designed life provided by Argonne National Laboratory. The relationship between strain amplitude and fatigue life can be described by Manson-Coffin and Langer equations,subsequently two equations are obtained. The elastic strain amplitude-reversals to failure,plastic strain amplitude-reversals to failure and plastic strain amplitude-cyclic stress amplitude all exhibit linear relationships in logarithmic coordinate.