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焊接钢结构的局部往往处于复杂的多轴非比例受力状态,在动力循环荷载作用下钢结构的局部失效破坏主要为多轴非比例疲劳所致。采用薄壁圆管试件进行了多轴加载条件下Q235B钢基材和焊接件的低周疲劳性能试验,对比了基材和焊接件的基本力学性能和低周疲劳性能;采用KBM和FS临界面准则进行了Q235B钢基材和焊接件的低周疲劳寿命预测。研究结果表明:多轴非比例加载路径下,Q235B钢基材及焊接件都存在明显的循环附加强化效应,导致其相对于单轴或多轴比例加载路径下的疲劳寿命更低;KBM准则能较好地预测多轴比例加载路径下的疲劳寿命,而对多轴非比例加载路径下的疲劳寿命的预测偏于不安全;FS准则通过考虑材料的非比例强化效应对多轴疲劳附加损伤的影响,能显著提高对多轴非比例加载路径下的疲劳寿命的预测精度。
Part of the welded steel structure is often in a complex multi-axial non-proportional stress state, the failure of the local failure of the steel structure under dynamic cyclic loading is mainly caused by multiaxial non-proportional fatigue. The low-cycle fatigue test of Q235B steel substrate and welded part under multiaxial loading conditions was carried out by using thin-walled circular tube specimens. The basic mechanical properties and low cycle fatigue properties of base material and welded part were compared. KBM and FS critical surface criteria The low cycle fatigue life prediction of Q235B steel substrate and weldment was carried out. The results show that under the multi-axial non-proportional loading path, the Q235B steel substrate and the weldment have obvious cyclic additional strengthening effect, which leads to lower fatigue life under the uniaxial or multi-axial proportional loading path. The KBM criterion The prediction of fatigue life under multi-axial non-proportional loading path is unsafe. The FS criterion adds additional damage to multi-axial fatigue by considering the non-proportional strengthening effect of material Influence, can significantly improve the prediction accuracy of fatigue life under multi-axial non-proportional loading path.