This study discusses the creep-fatigue strength for Mod.9Cr-1Mo steel at a high temperature of 823 K under multiaxial loading. Low cycle fatigue tests in various strain waveforms were performed with a hollow cylindrical specimen. The tests were conducted under a proportional loading with a fixed axial strain and a non-proportional loading with a 90-degree phase difference between axial and shear strains. The tests at different strain rates and the creep-fatigue tests at different holding times were also conducted to discuss the effects of stress relaxation and strain holding on the failure life. In this study, two types of multiaxial creep-fatigue life evaluation methods were proposed: the first method is to calculate the strain range using Manson’s universal slope method with considering a non-proportional loading factor and creep damage; the second method is to calculate the fatigue damage by considering the non-proportional loading factor using the linear damage law and to calculate the creep damage from the improved ductility exhaustion law. The accuracy of the evaluation methods is much better than that of the methods used in the evaluation of actual machines such as time fraction rule. The second method proposed by the authors showed the highest evaluation accuracy. The first evaluation equation is slightly less accurate than the second, but it is useful in that the evaluation procedure is easy.

本研究讨论了 Mod.9Cr-1Mo 钢在 823 K 高温下在多轴载荷下的蠕变疲劳强度。对空心圆柱试样进行了各种应变波形的低周疲劳试验。测试是在具有固定轴向应变的比例加载和轴向应变与剪切应变之间具有 90 度相位差的非比例加载下进行的。还进行了不同应变率的试验和不同保持时间的蠕变疲劳试验，以讨论应力松弛和应变保持对失效寿命的影响。在本研究中，提出了两种多轴蠕变疲劳寿命评估方法：第一种方法是使用曼森万能斜率法计算应变范围，同时考虑非比例加载因子和蠕变损伤；第二种方法是使用线性损伤定律通过考虑非比例载荷因子来计算疲劳损伤，并根据改进的延性耗竭定律计算蠕变损伤。评价方法的准确性远优于时间分数法则等实际机器评价方法。作者提出的第二种方法显示出最高的评估准确度。第一个评估方程的准确度略低于第二个，但它很有用，因为评估过程很简单。评价方法的准确性远优于时间分数法则等实际机器评价方法。作者提出的第二种方法显示出最高的评估准确度。第一个评估方程的准确度略低于第二个，但它很有用，因为评估过程很简单。评价方法的准确性远优于时间分数法则等实际机器评价方法。作者提出的第二种方法显示出最高的评估准确度。第一个评估方程的准确度略低于第二个，但它很有用，因为评估过程很简单。