High-temperature low-cycle fatigue failure characteristics and fatigue strength attenuation coefficient of welded joints of 316 stainless steel

To address the fatigue performance degradation of welded components of 316 stainless steel at elevated temperatures, the high-temperature fatigue behavior and fatigue attenuation coefficient were systematically studied from both material-level and structural-level perspectives. Low-cycle fatigue tests were conducted at 450 ℃ on the base metal, weld metal, and welded joint specimens of 316 stainless steel. The results show that within a total strain range of 0.5%–1.0%, the welded joint exhibits the highest cyclic stress response, followed by the weld metal, while the base metal shows the lowest cyclic stress response. Based on the difference in fatigue life between the base metal and welded joint, the ratio of the total strain ranges of the base metal to the welded joint at a specific number of cycles was calculated, and a recommended value of the fatigue strength attenuation coefficient for welded joints of 316 stainless steel at 450 ℃ was proposed. Based on the combined kinematic hardening model and improved damage model, the fatigue behavior of the welded joints of 316 stainless steel was accurately predicted. A theoretical framework for analyzing the fatigue strength attenuation coefficient of welded structures was proposed, and the influence of geometric characteristic factors on the fatigue attenuation coefficient of welded structures was revealed.