循环应力对磁记忆效应影响的试验研究

Experimental Study on the Effect of Cyclic Stress on Magnetic Memory Effect

为揭示循环应力对磁记忆效应影响的宏微观机制,基于拉-拉疲劳试验,采用TSC-2M-8应力集中磁检测仪研究了低碳钢缺口试件在不同循环周次下的磁记忆信号变化,提取了切向磁信号的多尺度模糊熵特征信息。基于粉纹法,采用自配的Fe_3O_4磁流体对试件表面固定区域进行了磁畴原位观察,得到不同疲劳周次下的磁畴形貌。研究结果表明:宏观磁信号将整个疲劳过程划分为早期的快速变化、中间阶段的趋于稳定、后期的迅速增大等三个阶段,利用多尺度模糊熵指标可以实现疲劳损伤的定量评价;试件在未受循环应力作用时表面的磁畴结构排列无序,加载后随疲劳循环的进行大部分磁畴形貌发生变化;试件表面漏磁场是循环应力引起内部磁畴结构变化的外在反映,二者具有一致性。

In order to reveal the macro-and micro-mechanism of the influence of cyclic stress on magnetic memory effect,the magnetic memory signal variations under different cyclic numbers of notched specimens made of low steel Q235 steel were investigated by using the stress concentration magnetic indicator TSC-2M-8 based on tension-tension fatigue experiments,and the multiscale fuzzy entropy characteristics of the tangential components were extracted simultaneously.The magnetic domain in situ in the fixed area of the specimen was observed by using the magnetic fluid Fe 3O 4 self-made based on the power grain method,and the corresponding magnetic domain morphology under different fatigue cycles was obtained.The results show that the whole fatigue process can be divided into three stages including the rapid early change,stable middle stage and rapid increase in the last stage by the macro-magnetic signals,and the multiscale fuzzy entropy can be applied to evaluate fatigue damage quantitatively.The surface magnetic domain structures are arranged disorderly when the specimen is not subjected to cyclic stress,and most change with the increasing fatigue cycles after loading.The leakage magnetic field on the surface of the specimen is the external reflection of the change of internal magnetic domain structures caused by cyclic stress,and they are in good agreement.