Fatigue failure of materials has a considerable impact on the safety of equipment in service. In this study, axially tensile and low cycle fatigue tests were conducted on a low alloy steel after accelerated thermal aged at 450 °C for 10,000 h. The experimental results indicate that the ultimate and yield strengths increase moderately, while the fatigue life of specimens experience a slight decrease in this circumstance. The fracture analysis demonstrates that the bainite breaking facilitates the fatigue crack initiation and propagation after thermal aging, which is accompanied by a decrease in plastic strain amplitude. Therefore, the plastic strain amplitude is considered as an indicator of thermal aging in fatigue life modeling for the low alloy steel. Finally, a novel life model that incorporates both aging time and temperature was proposed for rapid prediction of low cycle fatigue life. It is assumed that this model promotes reliable fatigue life prediction in low alloy steels under various thermal aging circumstances, as well as the extrapolation of fatigue performance of the material in service.

中文翻译：

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低合金钢长期热时效后的疲劳寿命建模


材料的疲劳失效对使用设备的安全性有相当大的影响。在本研究中，对低合金钢在 450 °C 下加速热时效 10,000 h 后进行了轴向拉伸和低周疲劳试验。实验结果表明，在这种情况下，极限强度和屈服强度适度增加，而试样的疲劳寿命略有下降。断裂分析表明，贝氏体断裂促进了热时效后疲劳裂纹的萌生和扩展，这伴随着塑性应变幅值的减小。因此，在低合金钢的疲劳寿命建模中，塑性应变幅值被视为热时效的指标。最后，提出了一种结合了老化时间和温度的新型寿命模型，用于快速预测低周疲劳寿命。假设该模型促进了低合金钢在各种热时效情况下的可靠疲劳寿命预测，以及对使用中材料的疲劳性能的推断。