The fatigue life of stainless steel under multiaxial loading conditions as a consequence of multiple damage effect occurring at elevated temperature is a topic of great importance. However, the interaction of creep, fatigue, and multiaxial non-proportional loading is poorly understood owing of a lack of experimental data obtained under multiaxial loading conditions. In the present study, data of previous creep–fatigue experiments performed on type 304 stainless steel under multiaxial loading conditions are summarized from available literature. These test results include the effects of strain rate, asymmetric strain waveform, and loading path on the creep–fatigue life of the stainless steel. Then, additional creep–fatigue tests are performed on the stainless steel under non-proportional loading conditions with four strain rates at 873 K in air. The applicability and limitations of several frequency-based life prediction models are discussed on the basis of the experimental results. Finally, an improved version of the frequency modified damage function (FMDF) model considering the effects of various loading path is proposed. The new model shows good correlation with the failure lives under multiaxial proportional and non-proportional loading conditions at elevated temperatures.

由于在高温下发生的多重损伤效应，不锈钢在多轴载荷条件下的疲劳寿命是一个非常重要的话题。然而，由于缺乏在多轴加载条件下获得的实验数据，人们对蠕变、疲劳和多轴非比例加载的相互作用知之甚少。在本研究中，从现有文献中总结了先前在多轴加载条件下对 304 型不锈钢进行的蠕变疲劳实验数据。这些测试结果包括应变速率、不对称应变波形和加载路径对不锈钢蠕变疲劳寿命的影响。然后，在空气中 873 K 的四种应变率下，在非比例加载条件下对不锈钢进行额外的蠕变疲劳试验。在实验结果的基础上讨论了几种基于频率的寿命预测模型的适用性和局限性。最后，提出了考虑各种加载路径影响的频率修正损伤函数（FMDF）模型的改进版本。新模型与高温多轴比例和非比例加载条件下的失效寿命具有良好的相关性。