基于磁记忆机理的焊缝疲劳累积损伤特征

通过20号钢焊接平板试件的拉-拉疲劳试验,研究了在单周期和多周期循环载荷下焊缝疲劳累积损伤的磁记忆信号特征。结果表明,由于试件内部初始状态下各处应力分布不均匀,焊缝原始磁信号表现为起伏较大;随着循环周次的增加,试件内部应力集中重新分布,信号趋于稳定;在周期累积循环试验中,磁记忆信号随着循环周次的增加出现螺旋上升的趋势,呈现出磁弹性效应变化特征;通过建立磁记忆信号与损伤度函数的模型,可根据磁记忆信号的变化准确判断裂纹扩展趋势,用于焊缝剩余寿命的预测。

Welded Joints Fatigue Cumulative Damage Behavior Based on Magnetic Memory Mechanism

In order to get metal magnetic memory（MMM） signal characteristics under single cycle tension loading and multi-cyclic fatigue loading, 20 steel welded plate specimens were tested by experiments. In single cycle tension experiments, the loading is increased from 20 kN to 60kN at 10kN interval space. In multi-cyclic tension fatigue experiments, the static loading is 35kN and the stress ratio is 1/6. The. results showed that MMM signals had fluctuations throughout the specimens under the initial state because of the residual stress distributed uniformly on welded joints. With the increment of tension loading, internal stress was redistributed again and MMM signal tended to be stable. In the cycle cumulative experiments, MMM signals show a loop-arising trend along with the increase of cycle numbers, reflecting the magnetic elastic variation effect. By establishing the relational model between the damage degree and the magnetic memory signal, the fatigue residual life of welded joints can be forecasted.