核级管道不锈钢316LN的低周疲劳特性研究

Research on Low-cycle Fatigue Characteristics of Nuclear Grade 316LN Stainless Steel Pipelines

在室温下,对核级管道不锈钢材料316LN试样进行了不同应变幅的低周疲劳试验研究,得到了316LN试样的循环应力-应变响应特征及低周疲劳寿命曲线。基于疲劳过程中、不同应变幅水平下,循环应力-应变迟滞回线的试验结果,分析了应力峰值、谷值和循环弹性模量随疲劳循环数的变化规律,研究了316LN试样的疲劳特性和疲劳寿命曲线特征,并与ASME疲劳设计曲线进行了对比。试验结果表明,试样初始循环表现出循环硬化,随后表现出循环软化直至失效;初始前10%疲劳寿命期内循环弹性模量缓慢下降,然后几乎保持不变,在达到80%~90%寿命后开始下降;Basquin和Manson-Coffin公式可以很好地描述0.2%~0.7%应变幅范围内的应变-疲劳寿命曲线。

Low cycle fatigue tests of316LN stainless steel specimens with different strain amplitudes were carried out at room temperature ,and the cyclic stress-strain response characteristics and low-cycle fatigue life of the stainless steel curve were obtained .Based on the test results of cyclic stress-strain hysteresis loop in the fatigue process at different levels of strain amplitudes ,the change rules of the peak and valley tensile stress and cyclic elastic modulus with the number of fatigue cycles were analyzed.The low-cycle fatigue characteristics and fatigue life curve characteristics of316LN specimen were investigated and compared with the ASME fatigue design curve.The results show that the316LN stainless steel specimens exhibited cyclic hardening at the beginning of cycles,and then exhibited cyclic softening until fractured.The cyclic elastic modulus decreased slowly during the period of the initial10% of fatigue life,and then remained almost unchanged,and begun to decrease after reaching 80%~90% of its lifetime.The Basquin and Manson-Coffin equations could well describe the strain fatigue life curve within the strain amplitude range of 0.2%~0.7%.