核电汽轮机末级长叶片材料的疲劳性能研究

Fatigue Property Investigation on Last Stage Blade Steel of Nuclear Power Steam Turbine

为了掌握核电汽轮机末级长叶片材料1Cr12Ni3Mo2VN的疲劳性能,开展了低周疲劳试验研究,测试了材料的疲劳循环响应特性、循环应力-应变曲线和应变-寿命曲线,比较了不同疲劳寿命预测模型的预测结果。结果表明:叶片材料在循环寿命的绝大部分期间都保持非常稳定的应力应变状态,仅在循环寿命初期表现出一定的循环软化特征;作为一种屈强比极高的材料,在循环周次105次及以上的疲劳寿命区域,循环塑性应变占总变形的比重变得非常小;断口形貌显示疲劳裂纹基本均起源于试样表面;Ramberg-Osgood模型和Manson-Coffin模型可以较好地拟合叶片材料的循环应力-应变曲线和应变-寿命曲线;Manson-Coffin模型和Langer模型对低周疲劳寿命预测均保持了较好的准确性;三参数幂函数能量模型在104循环周次以下的预测结果很好,需要更多的数据来提高其在更高循环周次的寿命预测准确性。

In order to investigate the fatigue properties of the last steam turbine blade steel 1 Cr12 Ni3 Mo2 VN,low cycle fatigue tests,including cyclic-stress,cyclic stress-strain and strain-life curves were conducted.The fatigue life was predicted according to the several theoretical models.Results show that the cycle stress amplitude keeps stable during the most of the fatigue life and the cyclic softening behaviour happens only in the early stage of cyclic life.As a high yield ratio steel,plastic strains are extremely small especially in the high cycle situation.Most of the fatigue crack sources are in the surface of the specimens according to the results of fracture morphology.The stress-strain curves and the fatigue life curves are fitted well using the Ramberg-Osgood model and the Manson-Coffin model.Both Manson-Coffin model and Langer model can match the fatigue life curves effectively.The three-parameter strain energy model may need more test data to improve the prediction accuracy in the high cycle area.