磁记忆是力磁效应的一种表现，目前关于力磁效应的基本规律及机理研究还没有统一的定论。为了进一步对磁记忆效应的机理及不同材料不同应力状态下磁记忆信号特征进行试验性的研究，对不同铁磁材料(Q235，20号钢，45号钢)圆棒试件进行静载拉伸试验，分别测量某固定点处在线加载和在线卸载2种不同应力状态下的磁记忆信号。试验结果表明：3种不同材料在线加载时磁记忆信号各表现出了不同的力磁效应；在线卸载时测得的磁记忆信号更能有利地分析构件的应力阶段；弹性阶段时磁荷梯度GF变化幅度不大，接近屈服阶段时，磁荷梯度变化幅度变大，可以利用磁荷梯度对低碳钢材料应力定量评价。试验结果为磁记忆效应机理研究提供了一定的依据，也为金属磁记忆检测的定量检测提供了潜在可能性。

Magnetic memory is a manifestation of stress-magnetic effect, currently, there is still no unified conclusion on the basic law and mechanism of stress-magnetic effect. In order to further carry out experimental study for mechanism of metal magnetic memory effect and study metal magnetic memory signal characteristics in different stress states of different materials, static tension tests on different ferromagnetic materials (Q235, 20 steel, 45 steel) round bar specimens were carried out, and magnetic memory signals on a fixed point under two different states which were online-loading and online-unloading stress were measured by metal magnetic memory testing. The results indicate that magnetic memory signals of three different materials under online-loading stress state show different stress-magnetic effects. The measured magnetic memory signal under online-unloading stress state is more favorable to analyze stress stage. The gradient of magnetic charge (GF) changes slightly at the elastic stage, but the changing amplitude of magnetic charge gradient becomes bigger near the yield stage, which can be used to quantitative evaluation of stress of low carbon steel. The test results provide some evidences for the mechanism of magnetic memory effect, and provide the potential possibility of quantitative inspection for metal magnetic memory testing.