基于金属磁记忆的钢结构焊缝疲劳试验

金属磁记忆检测技术已经在对接焊缝疲劳损伤检测方面有了诸多研究成果,但是目前的研究主要集中于对接焊缝的拉压疲劳,与实际结构中焊缝的弯拉疲劳过程之间存在差异.为此,本研究开展了含对接焊缝的工字钢梁疲劳试验,旨在真实地模拟实际工程中对接焊缝的疲劳开裂过程,揭示疲劳过程中磁信号的变化规律.试验结果表明:焊缝的初始焊接状态对于磁信号分布曲线的变化趋势有一定的影响,对于同一焊缝,当其初始磁信号曲线分布趋势相似时,其峰值及谷值随疲劳周次的变化趋势基本一致;研究发现,磁信号分布曲线的突变可以表征宏观疲劳裂纹出现,但是在疲劳稳定阶段,磁信号法向分量对于疲劳损伤的累计更加敏感;经过标准化处理后的矢量合成磁场平均值特征曲线可以表征焊缝疲劳的变化过程,捕捉到疲劳裂纹萌生的广义时间节点,从而对宏观疲劳裂纹的出现起到预警作用.

Fatigue Experiment of Steel Structure Weld Based on Metal Magnetic Memory

Many achievements have been made in the field of fatigue damage detection of butt welds by metal magnetic memory detection technology, but the current research mainly focuses on pull-pressing fatigue failure of butt welds. It is different from the bending-tensile fatigue failure of welds in actual structures. For this purpose, the steel I-beam with butt weld was used to perform fatigue experiments, in order to more realistically simulate the fatigue-cracking process of butt weld in actual engineering, and reveal the changing laws of magnetic signals during the fatigue process. The experiment results show that the change trend of the magnetic signal distribution curve is influenced by the initial welded state of the weld. When the initial magnetic signal curve distribution trend of the same weld is similar, the variation trend of the peak and valley values with the fatigue cycle is also basically same.The appearance of macroscopic fatigue cracks can be expressed as the sudden change of the magnetic signal distribution curve, but the normal component of the magnetic signal is more sensitive to the accumulation of fatigue damage during the stable fatigue stage. The change process of weld fatigue can be characterized as the variation of the normalized vector composite magnetic signal average characteristic curve and the generalized time node of fatigue crack initiation can be captured. So the appearance of macro fatigue cracks can be warned.