应力状态对磁记忆信号的影响

 通过对20#钢试件拉伸时表面磁场的在线测量和20#钢试件经过不同程度拉伸并卸载后的表面磁场的测量，研究应力状态对磁记忆信号的影响。20#钢进行拉伸试验时，在应力集中部位，当变形很小时磁场信号变化平缓；产生一定程度塑性变形后磁场信号变化相对剧烈；出现颈缩现象时磁场信号变化非常剧烈。经分析认为，磁记忆信号的变化与材料内部微观组织的状态有关，试件变形很小时，磁弹性效应对试件表面磁场的变化起主要作用;试件变形较大时，其表面磁场的变化主要受塑性变形区内位错聚集产生的微缺陷的影响。

Influence of Stress State on Magnetic Memory Signal

By testing the magnetic flux leakage distributions of specimens of steel 20 under uniaxial tensile loading condition and after removal of the applied uniaxial tensile load, at different loading levels, the influence of stress state on magnetic signal was studied. At the stress concentration zone, the magnetic signal change is found relatively gentle with slight deformation of the specimen, relatively acute with a certain plastic deformation of the specimen and very acute when necking of specimen happens. On analysis it is believed that the magnetic memory signal change is correlated to the state of the microstructure of the material. The specimen surface magnetic field change is mainly induced by the magneto-elastic effect when the deformation of the specimen is very small, and affected by the micro-flaws caused by the dislocation aggregation when the deformation of the specimen is relatively large.